Environmental Medicine Reports among care service nursery of … · Musculoskeletal diseases are disorders presumed to have developed after a long period ofexposure to unfavourable

Occupational and Environmental Medicine 1995;52:686-693

Reports of work related musculoskeletal injuryamong home care service workers compared withnursery school workers and the generalpopulation of employed women in Sweden

Yuichiro Ono, Monica Lagerstr6m, Mats Hagberg, Arvid Linden, Birgitta Malker

AbstractObjectives-To describe the nationwideoccurrence ofwork related musculoskele-tal injuries among all home care serviceworkers in Sweden, and to identify rela-tive risks and risk factors ofthe injuries.Methods-The study was based on workrelated injuries reported to the Swedishoccupational injury information systemin 1990-1. The work related musculo-skeletal injuries were divided into overex-ertion accidents and musculoskeletaldiseases. The incidence of the injuries infemale home care service workers wascompared with those in nursery schoolworkers and all other employed women inSweden.Results-In home care service workers,the annual incidence of injury fromoverexertion accidents and muscu-loskeletal diseases were 19-2 and 15 1 per1000 workers, respectively, which washigher than those in nursery schoolworkers and all employed women inSweden. For five injury locations includ-ing the back, all the age standardised rel-ative risks (SRR) of overexertionaccidents exceeded 4*0, and most ofthosefor musculoskeletal diseases were 1-5 ormore in home care service workers com-pared with all other employed women inSweden. Total duration of sick leave dueto overexertion accidents was 7-7 times,and musculoskeletal diseases 3 5 times,longer than in nursery school workers.National loss due to sick leave resultingfrom only musculoskeletal injuries inhome care service workers was about8-2% ofthe total work related sick leave inall employed women in Sweden, althoughthe number ofhome care service workersrepresented only some 5% of this popula-tion. Lifting other people was most fre-quently reported as the main risk causeof overexertion accidents in both kinds ofworkers.Conclusions-The results support thehypothesis that home care service work-ers have higher annual injury incidenceof musculoskeletal injuries than nurseryschool workers due to physically stressfultasks that are far less common in nurseryschool workers.

(Occup Environ Med 1995;52:686-693)

Keywords: injury reports; musculoskeletal; home care

In many developed countries, the need forhome care services is growing rapidly.Reasons for this growth include an increase inthe number of elderly people and a generaltendency of people to stay at home, which ispartly related to the development of medicalcare and reduced institutionalisation in hospi-tals due to cost containment pressure.' 2 Manystudies exist concerning the work relatedhealth risks associated with institutionalhealth care, 6 and detailed preventive mea-sures at work sites have been documented orstandardised.7 '0 On the other hand, littlework has been done on health problems inhome care service workers, although work inthe home is suspected to entail, as well as thesame risks as institutional health care, extraburdens on workers, as the work environmentis uncontrolled and less standardised."1

Recent research on work related risks asso-ciated with home health (medical) care indi-cates that back and other musculoskeletalaccidents and diseases are common in homenursing staff.""-3 Similarly, home care service(non-medical) workers were recently found tohave a higher prevalence of symptoms in theneck, shoulders, and low back than a controlgroup.14 In Sweden, there are about 110 000home care service workers who often work inprivate homes. The magnitude of the risksand factors related to the cause of workrelated musculoskeletal accidents and diseasesin these workers has not yet been clarified inthat country.

Patient handling has been considered to beone of the main risk factors of musculoskeletalproblems in nursing staff.6 15-18 It is suspectedthat home care service workers would havesimilar musculoskeletal troubles for similarreasons. Thus, we suspected that nurseryschool workers would have musculoskeletaltroubles associated with tasks such as liftingand carrying children. Their person handlingloads, however, would be less stressful thanthose of home care service workers becausethe people in their care are healthier andsmaller. Besides, home care service workershave other strenuous material handling tasks

National Institute ofOccupational Health,Division ofWork andEnvironmentalPhysiologyY OnoM LagerstromM HagbergNational Board ofOccupational Safetyand Health,Occupational InjuryInformation Division,S-171 84 Solna,SwedenA lindenB MalkerNagoya UniversitySchool ofMedicine,Department ofHygiene, 65Tsurumai-cho,Showa-ku, Nagoya466, JapanY OnoCorrespondence to:Dr Y Ono, Department ofHygiene, Nagoya UniversitySchool of Medicine, 65Tsurumai-cho, Showa-ku,Nagoya 466, Japan.Accepted 19 June 1995

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Reports ofwork related musculoskeletal injury among home care service workers compared with nursery school workers, etc

such as shopping, carrying, washing, cleaning,and cooking, which are far less common innursery school workers. Thus, it was consid-ered meaningful to compare the occurrence ofmusculoskeletal accidents and diseasesbetween home care service workers and nurs-ery school workers to estimate the differencesin the effect of work loads upon the muscu-loskeletal system in the two occupations.The aim of this investigation was to

describe the nationwide occurrence of workrelated musculoskeletal reports of accidentsand diseases in all home care service workersin the working population of Sweden, and toidentify relative risks and factors related to theaccidents and diseases by comparing homecare service workers with nursery schoolworkers and with all other employed womenin Sweden.

Subjects and methodsREPORTING SYSTEMIn Sweden the working population is compul-sorily insured against work related accidentsand diseases as well as against commutingaccidents. According to Swedish law, theemployers or self employed people mustreport all such accidents and diseases on aninquiry form that is sent to the labour inspec-torate. The work injury insurance scheme pre-sents a general description of what is to beconsidered as work related accidents and dis-eases, referring to those resulting from acci-dents and harmful influences at work. Besidesaccidents at work, the Work Injury InsuranceAct describes examples of substances, energyradiation, strenuous work operations, workingpostures, pressure, vibrations, noise, tempera-tures, etc, in the category ofwork related acci-dents and diseases. General infectiousconditions like colds are excluded.The work related musculoskeletal injuries

consist of overexertion accidents andmusculoskeletal diseases. If accidents can beconnected to a particular event or a specificpoint of time related to musculoskeletal over-exertion at work like lifting a heavy object, it isclassified as an overexertion accident. Otheraccidents like falls or vehicle accidents are notincluded in this category. Musculoskeletaldiseases are disorders presumed to havedeveloped after a long period of exposure tounfavourable ergonomic factors.The work injury insurance compensates, in

principle, for economic loss. Additional com-pensation for pain, incapacity, and otherinconveniences can be obtained from fundsbased on collective agreements betweenemployer organisations and trade unions. Thenumber of reports of work related musculo-skeletal injuries to the work injury insurancesystem is the subject of the present study, andthe number of injuries additionally compen-sated by the funds on collective agreementsare excluded. The information from thelabour inspectorate is collected in the occupa-tional injury information system that wasinstituted by the National Board ofOccupational Safety and Health in 1979.

Occupational accidents involving at least oneday of absence from work, and all workrelated diseases, are registered to form theofficial statistics of work related accidents anddiseases produced by the occupational injuryinformation system. The occupational injuryinformation system coding is based on inter-national classifications, including the interna-tional standard classification of occupation(ISCO) and the international standard classifi-cation of all economic activities (ISIC). Thereare also some individual occupational injuryinformation system codes for activities,events, external agencies, and so on.

STUDY BASEThis study is based on work related overexer-tion accidents and musculoskeletal diseasesreported to the occupational injury informa-tion system. All home care service workers(occupational code 154, ISCO 1958) withoccurrence of work related overexertion acci-dents or diseases registered in the occupa-tional injury information system in 1990 and1991 were selected. The incidence of workrelated accidents and diseases in home careservice workers was compared with that ofnursery school workers (occupational code153, ISCO 1958) and all other Swedishemployed women. Men were excludedbecause of their very small numbers in homecare service and nursery school workers.There were 105 006 home care service workersand 108 252 nursery school workers, repre-senting 4-9% and 5 0%, respectively, of thetotal population of employed women inSweden. These figures are taken from thenational population and housing census ofpeople registered on 1 November 1990.'9Those working at least one hour a week onaverage during October 1990 were counted asgainfully employed workers in this census. Weselected workers aged between 16 and 64years.

JOB DESCRIPTIONHome care service workers care for the elderlyor handicapped people in private or institu-tional homes. Their work comprises the careof the person, cooking, cleaning, necessaryshopping errands, and washing. The care ofthe person involves dressing and undressing,bathing, hair washing, and visiting a doctor,all of which sometimes requires person han-dling tasks including lifting. Home care ser-vice workers periodically clean the livingroom, bedroom, kitchen, entrance, and wash-room for the care client. When shopping, thehome care service workers sometimes have tocarry heavy bags of food and other domesticarticles. Washing tasks include not only wash-ing clothes but also ironing, folding andputting them away. In the census, 83% ofhome care service workers in Sweden work 20or more hours a week.

In Sweden, nursery school workers take careof the children aged one to six years. Thereare two types of nursery school teachers;preschool teachers, qualified by professionaleducation, and child minders. In this study,

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only child minders were chosen because theireducational background as professionals wassimilar to home care service workers. Averageincomes of the child minders and home careservice workers are also very similar inSweden. About 90% of nursery school work-ers in Sweden worked 20 or more hours aweek. Their work comprises the care and edu-cational activities for children-that is, meals,dressing and undressing, outings, play, paint-ing, bathing, dancing, reading, and so forth.There are occasional person handling activi-ties such as lifting and carrying children. Theweights, sizes, and physical coordinativecapacities of those receiving care, differgreatly from those of home care service work-ers. Nursery school workers usually take careof healthy children, whereas home care serviceworkers often look after elderly people withimpairment or clumsiness. In inspectional vis-its to more than 30 Swedish nursery schools,the authors found most of the chairs andtables for children were changed so as tomatch working heights. Supervisors in nurseryschools also commonly educate workers toavoid unsuitable work postures. Therefore, itwas thought unlikely that postural factors inperson handling had a remarkable effect onmusculoskeletal conditions in nursery schoolworkers in Sweden. Thus, person handlingtasks for nursery school workers are presum-ably physically less stressful than those forhome care service workers. Besides, strenuousmaterial handling tasks in home care serviceworkers are far less common in nursery schoolworkers, whose duties do not usually includelifting and carrying shopping materials, wash-ing, cleaning, and cooking. In the job inspec-tion and rough survey of social background,we did not find any evidence that the risks ofmusculoskeletal injuries in nursery schoolworkers are greater than those in home careservice workers.

EPIDEMIOLOGICAL ANALYSESTo determine the relative frequency of workrelated accidents and diseases, the annualinjury incidence rate (AIIR)/1000 workersstandardized to the age distribution of allemployed women in Sweden in the census,was calculated as

AIIR= 1000 05* N,, *Ni Ts NOT

where N,, = number of accidents and diseasesin home care service workers in each age stra-tum, NTi = total number of home care serviceworkers in each age group, Noz = number of allemployed women in each age group, and NOT =total number of all employed women. Themultiplication by 0-5 in the expression was toobtain the average of the 1990 and 1991 rates.Age groups for calculation were 16-19, 20-24,25-29, 30-34, 35-39, 40-44, 45-49, 50-54,55-59, and 60-64 years. This formula was alsoapplied to obtain the annual injury incidencerates for nursery school workers.The age standardized relative risks (SRRs)

of work related overexertion accidents andmusculoskeletal diseases in home care service

workers and nursery school workers com-pared with all other Swedish employedwomen were also calculated. This was doneby subtracting the number of home care ser-vice workers and nursery school workers fromthe whole population of employed women inSweden. Thus, the SRR is a ratio of twoannual injury incidence rates-that is, directlyage standardized rates. The SRR of theinjuries between home care service workersand nursery school workers was also calcu-lated, and the 95% confidence interval (95%CI) for the SRR was computed by a logarith-mic transformation.20 An age dependent trendin the proportion of injuries to workers wasalso tested by x' as proposed by Armitage.21

ResultsOVEREXERTION ACCIDENTS IN ALL WORKRELATED ACCIDENTSThe most common accidents were overexer-tion accidents related to exertion and falls inhome care service workers, which were alsomost frequently found in nursery schoolworkers (table 1). Vehicle accidents were thethird most common events in home care ser-vice workers but the least in nursery schoolworkers. The proportion of overexertion acci-dents (61 7%) to all work related accidentswas significantly higher (P < 0 01 by X2 test)in home care service workers than (33 1 %) innursery school workers.

MUSCULOSKELETAL DISEASES IN ALL WORKRELATED DISEASESThe distribution of main factors leading towork related diseases was similar for homecare service workers and nursery school work-ers (table 2). The most common disease wasrelated to musculoskeletal exertion in homecare service and nursery school workers. Thesecond and third most common diseases weredue to chemicals and social factors, whichwere far less frequent than musculoskeletaldiseases.

Table 1 Reported main events and the annual injuryincidence ofwork related accidents/1000 workers amonghome care service (HCS) and nursery school (NS)workers in Sweden (1990-1)

Occupations

Events HCS workers NS workers

Overexertion 19-2 3-5Fall 4-6 3-3Vehicle 1-9 0-3Blow 1-1 1-5Faulty step 1-0 0-8Object rest 0 9 0-6Object 0 8 0 3Other 1-2 0 7Total 30 7 11-0

Overexertion = musculoskeletal accidents related to exertion;fall = fall on the same or to a lower level; vehicle = accidentswith vehicle in motion except for commuting accident; blow =blow, kick, or other contact with other person; faulty step =faulty steps or step on a nail; object rest = contact with objectat rest; object = pressing, cutting, etc by handled object,instrument, etc.

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Table 2 Reported main factors and the annual incidenceof injuryfrom work related diseases/1000 workers amonghome care service (HCS) and nursery school (NS)workers in Sweden (1990-1)

Occupatioms

Factors HCS workers NS workers

Musculoskeletal 15-2 6-6Chemical 1-8 0-7Social 0 9 0-6Infectious 0-2 0-2Physical 0-1 0-1Other 0 3 0 3Total 18-5 8-5

Musculoskeletal = musculoskeletal diseases related toexertion; chemical = diseases related to chemical agents;social = organizational and social factors; infectious =infectious agents; physical = physical agents includingvibration.

ANNUAL INCIDENCE OF INJURY FROMOVEREXERTION ACCIDENTS AND MUSCU-LOSKELETAL DISEASESThe annual incidence of injury from over-exertion accidents and musculoskeletal dis-eases were much higher in home care serviceworkers than in nursery school workers andthe general population of all employed women(figs 1 and 2). With increasing age the annualincidence of injury from musculoskeletal dis-eases tended to increase in all groups, and thistendency was more pronounced in home careservice and nursery school workers than thatin the general population of all employedwomen. A significant increase in the propor-tion of overexertion accidents was found inthe age group 25-54 in home care service andnursery school groups (X2 = 5-43 P < 0 05,x2= 29*1 P < 0-01, respectively, fig 1). Theannual incidence of injury from overexertionaccidents was lowest in the 55-64 age groupin home care service workers. The mean (SD)duration of employment in the present occu-

Figure 1 Annualincidence of injury(AII)11000 workers dueto overexertion accidentsstratified by age. The agespecific AII calculated as amean in 1990-1 amonghome care service workerswas compared with thoseamong nursery schoolworkers and the Swedishgeneral population of allemployed women.

Figure 2 Annualincidence of injury(AII) /I 000 workers due tomusculoskeletal diseasesstratified by age. The agespecific AII calculated asan average in 1990-1among home care serviceworkers was comparedwith those among nurseryschool workers and theSwedish general populationof all employed women.

M Home care service workers= Nursery school workers

u 25 - m General population.M 20-

0

o 10 LLLL0

16-24 25-34 35-44 45-54 55-64 All

Age (y) (16-64)

M Home care service workersNursery school workers

U25 _ General population

4)015-10 oh- h h0

0

16-24 25-34 35-44 45-54 55-64 All

Age (y) (16-64)

pation of home care service workers withmusculoskeletal diseases was 11 5 (7 7) years,about three years longer than in home careservice workers with overexertion accidents.In nursery school workers with musculo-skeletal diseases, it was 12A4 (7 5) years, aboutthree years longer than in those with over-exertion accidents.

In home care service workers the highestannual injury incidence rates of all over-exertion accidents were found in the back(1 1), and in musculoskeletal diseases in theneck (5-0). This tendency was also seen innursery school workers and the general popu-lation of all employed women. Relatively highannual incidence of injury in home care ser-vice workers were also noticed for the neck(2-7) and shoulder or arm (2-7) for over-exertion accidents and for the back (4 0) andshoulder or arm (3-7) for musculoskeletaldiseases.

SRR OF OVEREXERTION ACCIDENTS ANDMUSCULOSKELETAL DISEASESWith regard to five injury locations: the neck,back, hand or wrist, shoulder or arm, and legor knee, all the SRRs of overexertion acci-dents exceeded 4 0 in home care serviceworkers when compared with all otheremployed women in Sweden (table 3). TheSRRs for the neck, shoulder or arm, and backwere notably high (more than seven), whereasthe SRRs of musculoskeletal diseases in homecare service workers were 1 5 or more for alllocations except the hand or wrist (table 3).For all overexertion accidents involving thefive body parts the SRR (95% CI) was 7-7(7 4-8 0) in home care service workers, andthat for all diseases was 1-7 (1-7-1-8).

In nursery school workers, the SRR ofoverexertion accidents exceeded 1-0 only forthe back (1-6) and leg or knee (1 9), and thoseof musculoskeletal diseases also slightlyexceeded 1 0 only for the back and leg or knee(table 3). The SRR (95% CI) in nurseryschool workers for all overexertion accidentsinvolving the five locations was 1-4 (1 3-1-5)v 0-7 (0 7-0 8) for all musculoskeletaldiseases.

Table 3 Age SRRs (95% CIs) ofoverexerion accidentsand musculoskeletal diseases among home care service(HCS) and nursery school (NS) workers compared withthe risks among the Swedish general population of all otheremployed women in 1990-1

HCS workers NS workers

SRR (95% CI) SRR (95% CI)

overexertion accidents:Neck 10-1 (9-1-11-3) 0-9 (0-7-1-2)Back 7-9 (7-5-8 3) 1-6 (1-4-1-7)Hand or wrist 4-7 (3-8-5-7) 0-9 (0-61-5)Shoulder or arm 8-4 (7-69-3) 1-0 (0-7-1-3)Leg or knee 4 9 (43-5 7) 1 9 (1-5-2-4)Total of five parts 7-7 (74-8-0) 1-4 (1-3-1-5)

Musculoskeletal diseases:Neck 1-5 (1-41-6) 0 7 (0S6-07)Back 2-7 (2-5-2 9) 1-2 (1-1-14)Hand or wrist 0-9 (0-8-1-0) 0-3 (0-2-0-4)Shoulder or arm 1-6 (1-5-1-7) 0-6 (0S6-07)Leg or knee 2-5 (2-2-2 8) 1-3 (1-0-1-6)Total of five parts 1-7 (1-7-1-8) 0 7 (0 7-0 8)

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Table 4 Age SRRs (95% CIs) of overexertion accidentsand musculoskeletal diseases among home care service(HCS) workers compared with the risk among nurseryschool (NS) workers

SRR (95% CI)

Overexertion accidents:Neck 114 (84-154)Back 5-1 (4 6-5-7)Hand orwrist 5 0 (3-1-8-1)Shoulder or arm 8 5 (6 4-11 4)Leg or knee 2 6 (2 0-3 4)Total of five parts 5 5 (5-1-6 0)

Musculoskeletal diseases:Neck 2-3 (2 0-2-6)Back 2-2 (1-9-2-5)Hand orwrist 3 2 (2-3-4 5)Shoulder or arm 2 4 (2 1-2 8)Leg or knee 2-0 (1-5-2-6)Total of five parts 2-3 (2-1-2 5)

Figure 3 Average andtotal duration of sick leavedue to overexertionaccidents among homecare service workerscompared with thoseamong nursery schoolworkers in 1990-1. 00

0H

Figure 4 Average andtotal duration of sick leavedue to musculoskeletaldiseases among home careservice workers comparedwith those among nurseryschool workers in 1990-1.

120 r

100

Home care serviceworkers (total)

100 Nursery school 100workers (total)Home care service

80 workers (average) - 80i Nursery school X

60 W workers (average) 60 v

40 40-4

20 20

16-24 25-34 35-44 45-54 55-64Age (y)

_I Home care serviceworkers (total)Nursery schoolworkers (total)Home care serviceworkers (average)

_,__ Nursery schoolworkers (average)

is00 80xI,,, 60

A) 040

H 20

0O1 - l l _ _

16-24 25-34 35-44 45-54Age (y)

Numbers of people0 500 1000 1500 2000

Other person (handling)Construction parts

Materials and goods

Lifting machines or vehicles

Handling tools or implements

Air conditioningE

Electrical equipment l

Other converting machines

Other factors

Lifting

m Exertion

- 160

The SRRs were higher for overexertionaccidents than for musculoskeletal diseases inboth home care service and nursery schoolworkers. Comparison of overexertion acci-dents in home care service workers with nurs-ery school workers showed that the SRRswere 5-0 or more for all locations except theleg or knee (table 4) v 2-0 or more for muscu-loskeletal diseases.

SICK LEAVEIn home care service workers, the mean andtotal duration of sick leave for overexertionaccidents were 35 0 and 139 633 days,respectively, and 101 6 and 325 654 days formusculoskeletal diseases. With increasing age,the mean and total duration tended toincrease notably in both overexertion acci-dents and musculoskeletal diseases except inthe oldest age group for overexertion acci-dents (figs 3 and 4). The average and totalduration of sick leave were 24-8 and 18 235days, respectively, for the overexertion acci-dents in nursery school workers, and 78A4 and94 377 days for the musculoskeletal diseases.With increasing age of nursery school work-ers, the average duration tended to increase,whereas total duration was greatest in the 35-44 age group (figs 3 and 4).

Thus, total duration of sick leave due tooverexertion accidents was 7 7 and due tomusculoskeletal diseases was 3-5 times greaterin home care service workers than in nurseryschool workers. Total loss due to sick leaveresulting from overexertion accidents andmusculoskeletal diseases was nearly 465 000days in home care service workers in 1990-1.This figure corresponded to about 8-2% ofall work related sick leave days (5 655 000days) including all types of accident and dis-ease in all employed women in Sweden in1990-1.

140MAIN RISK FACTOR

120 The factors registered as having a primary100 > relation to the reported cause of overexertion

* accidents were classified in two different ways80 U)* -that is, classification by the type of objects

*60 , being handled and by activities involving lift-- 40 < ing or other exertion. In home care service

_20 workers, handling another person was most20 frequently reported (n = 3009, 75.7%) to be

55-64 0 the main risk factor, other factors representingonly some 25% (n = 967) of all reports (fig 5).In the activities classification, lifting repre-sented 81.2% (n = 3229) of all reports and

2500 3000 94-7% (n = 2851) of those involved handlinganother person. In nursery school workers,handling of another person was also most fre-quently reported (n = 412, 56 5%) to be themain risk factor and 88-1% (n = 363) of thetasks were also related to lifting activities.

Person handling accounted for 55-1% (n =1766) of the main risk factors for the musculo-skeletal diseases in home care service workers,and 79-5% (n = 957) of those in nurseryschool workers. Risk factors remainedunknown in 29-2% of musculoskeletal dis-

vics workers eases in home care service workers and 11 -2%in 1990-1. of those in nursery school workers.

Figure 5 Main risk factors of overexertion accidents among home care sernzcategorised by the objects handled and activities with lifting or other exertion

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DiscussionIMPORTANCE OF OVEREXERTION ACCIDENTSAND MUSCULOSKELETAL DISEASES IN HOMECARE SERVICE AND NURSERY SCHOOL WORKERSThe annual incidence of injury and SRRs ofoverexertion accidents and musculoskeletaldiseases were notably higher in home care ser-

vice workers than in the general population ofall other employed women in Sweden. Thiswas found not only for the back, but also theneck, shoulder or arm, hand or wrist, and legor knee-that is, high risk locations. Theannual incidence of injury from back acci-dents was higher than that in nurses' aides(8-92) in a study by Engkvist et al.22 Johanssonreported high odds ratios (ORs, 1-39-1 52)for symptoms in the neck, shoulders, and lowback in home care service workers comparedwith a control group of office workers, teach-ers, child care workers, and others.'4 Theseresults accord with those in our study, but our

data showed higher levels.The annual incidence of injury and SRRs

of overexertion accidents and musculoskeletaldiseases were higher in home care serviceworkers than in nursery school workers. Thissupports our hypothesis that incidences ofoverexertion accidents and musculoskeletaldiseases would be higher in home care serviceworkers than in nursery school workers.Home care service workers will have to per-

form more stressful person and material han-dling tasks such as care of the elderly,shopping and carrying, washing, cleaning, andcooking jobs that are far less common innursery school workers. It should be notedthat the lower limit of the 95% CI of SRRswas greater than 1 0 for accidents to the backand leg or knee, and back diseases in nursery

school workers. Some studies showed that theneck, shoulders, arms, and back were highrisk locations for work related musculoskeletalproblems in nursery school workers inJapan."'6 In the occupational injury informa-tion system in Sweden, however, we foundthat SRRs were less than 1-0 for the neck andshoulder and arms in nursery school workers.There have been no international comparativestudies on working conditions and work loadof nursery school workers. Thus, the reasons

for this discrepancy in the results of investiga-tions conducted in two countries should bethe subject of future studies.

National loss due to sick leave resultingfrom overexertion accidents and musculo-skeletal diseases accounted for about 8-2% ofall work related sick leave in all Swedish work-ing women, although the number of homecare service workers represented only some

5% of this population. Thus, it is consideredimportant and urgent for the national econ-

omy to decrease work related overexertionaccidents and musculoskeletal diseases inhome care service workers.

Relative risks of neck accidents and dis-eases were as high as those of back accidentsand diseases in Swedish home care serviceworkers. Makela et al studied a representativepopulation sample of 8000 people in Finlandand reported that ORs for chronic neck pain

syndrome were increased by some determi-nants such as physical and mental stress atwork, and the neck pain syndrome was alsoclosely associated with low back pain.27Linton also reported that lifting and uncom-fortable work posture were found to increasethe risk of both neck and back pain problemsin the questionnaire study of more than20 000 Swedish workers.2n Thus, the highrisks of neck problems in home care serviceworkers do not seem to be unusual, althoughthe biological mechanism relating neck symp-toms to back problems remains unclear.

EFFECT OF AGEThe annual incidence of injury from over-exertion accidents and musculoskeletal dis-eases tended to increase with the age of homecare service workers. In general this would bepartially attributed to pathological changes inthe musculoskeletal system or decreases inmuscular strength and other physical capabilitydue to aging.29 There must be more factorsaggravating musculoskeletal conditions ofhome care service and nursery school workersthan in the general population, because wefound a more prominent age dependentincrease in home care service and nurseryschool workers. As person handling is one oftheir routine tasks, home care service andnursery school workers need more physicalstrength than some other workers do. Henceit is supposed that the effect of work load onthe musculoskeletal system would be moresignificant in home care service and nurseryschool workers than in other occupations iftheir capabilities are reduced by aging.Preventive measures, including decrease ofwork load corresponding to the age of theworkers, would be essential especially forhome care service and nursery school workers.The lowest annual incidence of injury from

overexertion accidents was found in the55-64 age group in home care service work-ers. In Sweden, early retirement in this agegroup was not uncommon.30 In the 1989statistics, the number of early retirements per1000 people was 174-0 in the 55-59 agegroup and 330 4 in the 60-64 group, but lessthan 100 in every other five year age group.Aronsson et al reported that newly retiredpeople with early retirement pensions hadhigher complaint scores of back, shoulder,and arm pain than did those with retirementdue to maturation of age.3' In another study ofFinnish workers representative of the generallabour force over 35 years of age, the mostcommon ground for early retirement, espe-cially in older workers, was the fear of losing,or the loss of, their health and working capac-ity.32 Thus, it is suspected that the annualincidence of injury in the oldest age group inSweden at least could be largely biased bymuch early retirement and does not reflect thereal situation in this group.

RISK FACTORSStudies on the relation of patient handlingtasks to episodes of back pain, overexertionaccidents, and musculoskeletal diseases sup-

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Ono, Lagerstrom, Hagberg, Lindtn, Malker

port the notion that person handling tasks canbe the main risk factors of overexertion acci-dents and musculoskeletal diseases in homecare service workers.6 15-18 Recent studies alsosuggest risk factors of musculoskeletal prob-lems in home care service workers. Johanssonreported that the prevalence of musculoskeletalsymptoms in home care service workers wasassociated with both psychosocial factors andphysical work load.'4 In his questionnairestudy, psychosocial factors consisted of super-visory attitude, influence on and control ofwork, stimulus from the work, relations withfellow workers, and psychological work load.He also included some physical work load(lifting, repetitive and monotonous move-ment, unsuitable postures, trunk flexion, andhands above shoulder height). In the reporton home care service workers by Aronsson etal, early retirement pensioners had high scoresfor musculoskeletal symptoms and complaintsof working conditions before retirement,including difficulty in walking and shopping,uncomfortable work position, work undertime pressure, and effort to keep up.3' Torgenet al studied the work load of nursing aides inthe home care services and reported that theyspent most of their working day walking orstanding, which could be very tiring for theback and feet.33 These authors also reportedthat the amount of the day spent in poor backpostures and time spent on cleaning tasks cor-related positively to perceived exertion and tosick leave. As the work of home care serviceworkers contains tasks resembling those ofnursing aides, similar physical strain couldcause their musculoskeletal problems.The mean duration of employment in the

present occupation was 11-5 years in homecare service workers with musculoskeletal dis-eases, and about three years longer than thatin those with overexertion accidents in ourstudy. This may imply the long term cumula-tive effects of many risk factors on the devel-opment of musculoskeletal diseases. There isno information on the weekly working hoursof home care service workers with musculo-skeletal injuries registered in the occupationalinjury information system. The number ofpast occurrences of the diseases was alsounavailable in the occupational injury infor-mation system, making it impossible to deter-mine whether the reported injuries hadoccurred for the first time or not. Thus, wewere unable to work out cumulative workinghours from the beginning of employment tothe first occurrence of musculoskeletal dis-eases. We think that the occupational injuryinformation system should have some addi-tional variables to increase its use for epidemi-ological studies, including working hours ofthe reported cases and the number of the pastoccurrence of the injuries.

In our study, the main risk factor reportedto the occupational injury information systemwas person handling in home care serviceworkers, which is accompanied not only bylifting activity but also trunk flexion andunsuitable postures. The studies already men-tioned suggested many other factors that

influence musculoskeletal conditions of homecare service workers.'4 31 33 Besides, our studyonly dealt with limited factors reported tohave a primary relation with musculoskeletalinjuries and no information was available as tothe extent to which other factors might con-tribute to the development of injuries.Considering the many risk factors formusculoskeletal injuries and the highly vari-able nature of the work, the data and studiesremain insufficient to reach any definite con-clusion about risk factors in home care serviceworkers. Thus, field studies on work load andepidemiological investigations with temporaldesign for analysing causes of many factors,are necessary in the future.

EXTRAPOLATION TO OTHER COUNTRIESIt might be supposed that relative risks ofmusculoskeletal injuries are similarly high inhome care service workers in other developedcountries if they have analogous strenuoustasks in their work. International comparisonof the Swedish statistics may be almost impos-sible for work related injuries because criteriafor work related injuries vary widely fromcountry to country. In Japan, for example, thenumber of musculoskeletal diseases withoutaccidental origin treated according to injurycompensation law for workers is less than 2%of that reported in the occupational injuryinformation system in Sweden.'934

POSSIBLE BIASThere are some studies on underreporting tothe occupational injury information system.35-37Larsson et al made a comparative study ofwork related accidents in three differentregistries-that is, hospital and insurance reg-istries, and the occupational injury informa-tion system in the municipality of Umea.35They found that 27% of cases that shouldlegally have been reported to the occupationalinjury information system were missing.Engkvist et al also reported that the incidenceof low back accidents estimated in their ques-tionnaire study was 20 times higher thanreported in the occupational injury informa-tion system for workers in a nursing district.37Thus, the actual numbers of accidents anddiseases could be far greater than the annualincidence of injury based on the occupationalinjury information system, although the occu-pational injury information system may reflectmore severe cases than the study populationdata, which is based on complaints only.As the occupational injury information sys-

tem is based on reports from employers thatare often initiated by workers, motives for reg-istration could be biased in some occupationalsectors by psychosocial factors, includingunion activities, workers' knowledge of workrelated accidents and diseases, and relationsbetween labour and management. Reportingof work related accidents and diseases isstrongly urged by law in all occupational sec-tors in Sweden, and therefore these differ-ences in reporting attitudes might not be verylarge in various occupations. To our knowl-edge, we are not aware of any major con-

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founders in home care service and nurseryschool workers that could have influenced thereporting to the occupational injury informa-tion system. This reporting issue requires fur-ther study.

In accidents, risk factors are usually regis-tered as events when they have just occurred.In general, the records seem to be reliablebecause accidental events often occur sonoticeably as to be observed by other workers.On the other hand, in musculoskeletal diseasethe onset is usually unclear and records of riskfactors are inevitably considered speculativeand anecdotal. This may partially explain whynearly 30% of the records lacked any descrip-tion of risk factors. Although acknowledgingthis drawback, it should nevertheless be notedthat person handling tasks were indicated as arisk factor in more than half of the records ofmusculoskeletal diseases.

ConclusionsStatistics show that national loss due tomusculoskeletal injuries has been extremelyhigh in Sweden. Thus, it is considered impor-tant and urgent for the Swedish nationaleconomy that the number and severity ofthese injuries be reduced in home care serviceworkers. The present results clearly supportthe hypothesis that home care service workershave higher annual incidence of injury frommusculoskeletal injuries than nursery schoolworkers due to physically stressful tasks thatare far less common in nursery school work-ers.

1 American Medical Association Council on ScientificAffairs. Council report, home care in the 1990s. JAMA1990;263:1241-4.

2 Swedish National Board of Occupational Health.Ordinance on care and assistance in private homes.Arbetarskyddssamling f6rfattningssamling 1990;18:1992.(In Swedish.)

3 Magora A, Taustein I. An investigation of the problem ofsick-leave in the patient suffering from low back pain.Ind Med 1969;38:80-90.

4 Klein BP, Jensen RC, Sanderson LM. Assessment ofworkers' compensation claims for back strains/sprains.J Occup Med 1984;26:443-8.

5 Marchette L, Marchette B. Back injury: a preventableoccupational hazard. Orthopaedic Nursing 1985;4:25-9.

6 Harber P, Elizabeth B, Gutowski M, SooHoo K, Lew M,Roman A. Occupational low-back pain in hospitalnurses. J7 Occup Med 1985;27:518-24.

7 Standards Association of Australia. Guide to the lifting andmoving ofpatients. Part 1-Safe manual hfting and movingof patients. North Sydney: Standards Association ofAustralia Standards House, 1982. (Australian Standard2569.)

8 Stubbs DA, Baty D, Buckle PW, Fernandes AF, HudsonMP, Rivers PM, et al. Back pain in nurses, summary andrecommendations. Surrey: University of Surrey, 1986.

9 Lloyd P, Tarling C, Troup JDG, Wright B, CharlesworthD. The handling ofpatients. 2nd ed. Middlesex: Back PainAssociation. London: Royal College of Nursing, 1987.

10 Stockholm County Council. The Stockholm training concept.Stockholm: Stockholm City Council,1987. (InSwedish.)

11 Smith AW, White MC. Home health care, occupationalhealth issues. American Association of Occupational HealthNurses Journal 1993;41: 180-5.

12 Knibbe JJ, Friele RD. Back pain and patient lifting innurses working in home care. In: Hagberg M, HofnannF, St6Bel U, Westlander G, eds. Occupational health forhealth care workers: proceedings of the 1st internationalcongress on occupational health for health care workers;September 1992. Landsberg: Ecomed verlagsgesellschaftmbH, 1993:312-4.

13 Toomingas A. The health situation among Swedish healthcare workers. Occupational health for health care workers.In: Hagberg M, Hofmann F, Stol6el U, Westlander G,eds. Occupational health for health care workers: proceedingsof the 1st international congress on occupational health for

health care workers; September 1992. Landsberg: Ecomedverlagsgeseilschaft mbH, 1993:37-42.

14 Johansson jA. Psychosocial factors, physical load, andsymptoms from the neck, shoulders and back amonghome care workers. In: Hagberg M, Hofmann F. StolBelU, Westlander G, eds. Occupational health for health careworkers: proceedings of the 1st international congress on occu-pational health for health care workers; September 1992.Landsberg: Ecomed verlagsgesellschaft mbH,1993:326-31.

15 Harber P., Elizabeth B, Vojtecky M, Rosenthal E,Shimozaki S, Horan M. Nurses' beliefs about cause andprevention of occupational back pain. J7 Occup Med1988;30:797-800.

16 Lortie M. Analyse comparative des accidents declares pardes proposes hommes et femmes d'un h6pital ghria-trique. Journal of Occupational Accidents 1987;9:59-81.(In French with English abstract.)

17 Owen BD. The need for application of ergonomic princi-ples in nursing. In: Asfour SS, ed. Trends in ergonomicshuman factors IV. New York: Elsevier, 1987:831-8.

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19 Official Statistics of Sweden, National Board ofOccupational Safety and Health, Statistics Sweden.Occupational risks 1990-1991, occupational accidents anddiseases. Stockholm: Svenskt Tryck AB, 1994. (InSwedish with English summary.)

20 Ahlbom A. Biostatistics for epidemiologists. Boca Raton:Lewis, 1993.

21 Armitage P. Tests for linear trends in proportions and fre-quencies. Biometrics 1955;11:375-86.

22 Engkvist I-, Hagberg M, Linden A, Malker B. Over-exer-tion back accidents among nurses' aides in Sweden.Safety Science 1992;15:97-108.

23 Nagira T, Suzuki J, Oze Y, Ohara H, Aoyama H.Cervicobrachial and low-back disorders among schoollunch workers and nursery-school teachers in compari-son with cash-register operators. J Hum Ergol (Tokyo)1981;10:117-24.

24 Kurumatani N, ilDi M, Katagi K. A study on occupationalcervicobrachial disorder (OCD) of nursery school teach-ers based on subjective symptoms related to OCD.Japanese Journal ofIndustrial Health 1984;26:389-96. (InJapanese with English abstract, figures, and tables.)

25 Ono Y, Hosokawa M, Maeda K, Miyao M. 1987.Occupational cervicobrachial disorders (OCD) andassociated back pain in Japan. In: Osterholz U, KarmausW, Hullmann B, Ritz B, eds. Work-related musculoskeletaldisorders: proceedings of an international symposium; June1985. Bonn: Wirtschaftsverlag NW, 1987:279-305.

26 Ono Y, Shimaoka M, Hiruta S, Shibata E, Huang J,Takeuchi Y, et al. Analysis of ergonomic problems in thework at nursery schools. NagoyaJ Health Physical Fitnessand Sports 1990;13:91-100. (In Japanese with Englishabstract, figures, and tables.)

27 Mdkela M, Heliovaara M, Sievers K, Impivaara 0. Knekt P,Aromaa A. Prevalence, determinants, and consequencesof chronic neck pain in Finland. Am J Epidemiol1991;134:1356-67.

28 Linton SJ. Risk factors for neck and back pain in a workingpopulation in Sweden. Work and Stress 1990;4:41-9.

29 Parker KG, Imbus HR. Cumulative trauma disorders.Chelsea, MI: Lewis, 1992.

30 Westerholm P., Baltzari L. The social security systems inSweden and its utilisation by the elderly work force. In:Kilbom A, ed. Early retirement and social security systems.the situation of workers in Denmark, Finland, Norway, andSweden. Arbete och Halsa 1992:29. Solna: NationalInstitute of Occupational Health, 1992:39-59.

31 Aronsson G, Astvik W, Thulin A-B. Working conditions andoccupational exclusion among home care workers inStockholm. A comparison between a group of care givers onearly retirement/disablement pensions and a group of healthy,now retired care givers. Arbete och Halsa 1993:26. Solna:National Institute of Occupational Health, 1993. (InSwedish with English summary.)

32 Huuhtanen P, Piispa M. Work or retirement: alternativesof elderly people in the 1990s. In: Kilbom A, ed. Earlyretirement and social security systems. The situation of work-ers in Denmark, Finland, Norway and Sweden. Arbete ochHalsa 1992:29. Solna: National Institute of OccupationalHealth, 1992:60-6.

33 Torghn M, Nygard C-H, Kill C, Kilbom A. Physiologicalstrain and its relation to work tasks and physical capacityamong elderly nursing aides in home care service. Proceedingsof 24th congress of the international commission on occupa-tional health; September 1993. Nice: ICOH, 1993:282.

34 Japanese Association of Public Health Statistics. The trend ofnational health. 1993. (In Japanese.)

35 Larsson T, Bjomstig U. The epidemiology of occupationalaccidents: three ways to measure the problem in aSwedish municipality. Journal of Occupational Health andSafety of Australia and New Zealand 1990;6:39-52.

36 Jacobsson B, Schelp L. One-year incidence of occupa-tional injuries among teenagers in a Swedish ruralmunicipality. Scand J Soc Med 1988;16:21-5.

37 Engkvist IL, Wigaeus Hjelm E, Hagberg M, Olivius G,Hellstrom S. Musculoskeletal accidents at work and freetime among health care workers. Proceedings of the 48thannual general meeting of the Swedish Society of Medicine;1991 Nov; Stockholm. Stockholm: Swedish Society ofMedicine 1991. (In Swedish.)

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