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Eur Spine J (2008) 17 (Suppl 1): S192-S198DOI 10.1007/s00586-008-0636-7

Reprinted with permission from Lippincott Williams & Wilkins, Côté P, Kristman V, Vidmar M, et al., The Preva-lence and Incidence of Work Absenteeism Involving Neck Pain, A Cohort of Ontario Lost-Time Claimants, SPINE, Volume 33, Number 4S, pp S192–S198

SPINE Volume 33, Number 4S, pp S192–S198©2008, Lippincott Williams & Wilkins

The Prevalence and Incidence of Work AbsenteeismInvolving Neck PainA Cohort of Ontario Lost-Time Claimants

Pierre Cote, DC, PhD,*†‡§ Vicki Kristman, PhD,*†‡§ Marjan Vidmar, MD, MSc,§Dwayne Van Eerd, MSc,†§ Sheilah Hogg-Johnson, PhD,†§ Dorcas Beaton, PhD,†§�

and Peter M. Smith, PhD§

Study Design. Cohort study.Objective. To measure the prevalence and incidence

of work absenteeism involving neck pain in a cohort ofclaimants to the Ontario Workplace Safety & InsuranceBoard (WSIB).

Summary of Background Data. According to workers’compensation statistics, neck pain accounts for a smallproportion of lost-time claims. However, these statisticsmay be biased by an underenumeration of claimants withneck disorders.

Methods. We studied all lost-time claimants to theOntario WSIB in 1998 and used 2 methods to enumerateneck pain cases. We report the prevalence and incidenceof neck pain using 2 denominators: (1) annual number oflost-time claimants and (2) an estimate of the Ontarioworking population covered by the WSIB.

Results. The estimated percentage of lost-time claim-ants with neck pain ranged from 2.8% (95% CI 2.5–3.3)using only codes specific for neck pain to 11.3% (95% CI9.5–13.1) using a weighted estimate of codes capturingneck pain cases. The health care sector had the highestpercentage of claims with neck pain. The annual inci-dence of neck pain among the Ontario working popula-tion ranged from 6 per 10,000 full-time equivalents (FTE)(95% CI 5–6) to 23 per 10,000 FTE (95% CI 20–27) depend-ing on the codes used to capture neck pain. Male workersbetween the ages of 20 and 39 years were the most likelyto experience an episode of work absenteeism involvingneck pain.

Conclusion. Neck pain is a common and burdensomeproblem for Ontario workers. Our study highlights theimportance of properly capturing all neck pain caseswhen describing its prevalence and incidence.

Key words: neck pain, work, sick leave, epidemiology,prevalence, incidence, workers’ compensation.

Neck pain is a well-recognized source of disability in theworking population.1 Surveys of workers suggest thatthe annual prevalence of activity limitations related toneck pain varies from 11.0% in the UK to 14.1% inQuebec, Canada.2,3 However, these statistics do notagree with claim rates reported by Workers’ Compensa-tion Boards. According to workers’ compensation statis-tics, work-related neck pain represents a minor healthburden to society.

For example, in 2005 in Saskatchewan, Canada, neckpain claims accounted 1.7% of all claims accepted by theWorkers’ Compensation Board.4 During the same pe-riod in Ontario, claims related to the cervical and tho-racic regions accounted for 4.5% of all lost-timeclaims.5 Moreover, Silverstein et al6 reported that be-tween 1990 and 1998, 3.0% of annual claims to theWashington State Department of Labor and Industrieswere for “non-traumatic” “soft tissue disorders of theneck.” In Washington State, the annual incidence ofneck pain lost-time claims was 19.1 per 10,000 full-time equivalents (FTE).6

The discrepancy between survey and administrativestatistics is partly attributable to differences in neck painseverity (i.e., lost-time claimants likely represent the pro-portion of workers with worse injuries). However, it isalso possible that workers’ compensation statistics do notaccurately capture the true burden of disability related tospecific disorders. Although worker’s compensationrecords offer a rich source of data for epidemiologic re-search, their use may lead to erroneous estimates of theprevalence and incidence of work absenteeism related toa type of disorder.

Reporting (underreporting and inaccurate reporting)and diagnostic uncertainty can lead to measurement er-ror when using workers’ compensation data in re-search.7–9 However, for injuries such as soft tissue disor-ders of the neck, an additional source of systematic errormay be related to the coding protocols used by workers’compensation boards. According to these protocols, an

From the *Centre of Research Expertise in Improved Disability Out-comes (CREIDO), University Health Network Rehabilitation Solutions,Toronto Western Hospital, Toronto, Canada; †Departments of PublicHealth Sciences and Health Policy, Management and Evaluation, Uni-versity of Toronto, Canada; ‡Division of Health Care and OutcomesResearch, Toronto Western Research Institute, Toronto, Canada; §In-stitute for Work & Health, Toronto, Canada; ¶Graduate Departmentof Rehabilitation Science, University of Toronto, Toronto, ON; and�Mobility Program Clinical Research Unit, St Michael’s Hospital, Uni-versity of Toronto, Toronto, ON.Supported by a grant of The Ontario Ministry of Health and LongTerm Care (Special Chiropractic Research Fund), Canadian Institute ofHealth Research (to P.C., D.B., and V.K.), and Canadian Institute forthe Relief of Pain and Disability’s (formerly the Physical MedicineResearch Foundation) Woodbridge Grants and Awards Program (toV.K.).The manuscript submitted does not contain information about medicaldevice(s)/drug(s).Institutional funds were received in support of this work. No benefits inany form have been or will be received from a commercial party relateddirectly or indirectly to the subject of this manuscript.Ethics Board Approval number: University of Toronto (Protocol Ref-erence: 00011747).Address correspondence and reprint requests to Pierre Cote, DC, PhD,Toronto Western Hospital, Fell Pavilion 4-124, 399 Bathurst Street,Toronto, ON, Canada M5T 2S8; E-mail: [email protected]

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injured worker with multiple injuries would only havehis/her “most severe injury” coded and recorded in thedatabase. Therefore, sprain and strains of the cervicalspine would not be coded because they are given a lowcoding priority relative to other injuries such as concus-sions and lacerations. We studied this potential source ofbias and found that omitting to count these claimantswould lead to a gross underestimation of the true num-ber of lost-time claimants with soft-tissue disordersinvolving the neck. Specifically, we found that thenumber of lost-time claimants with soft-tissue disor-ders to the neck varied from 88% in those coded witha disorder of the neck region, to 69% for claimantscoded with disorders of the back and 55% for claim-ants with a brain injury (concussion).10 The objectiveof this article is to report on the prevalence and inci-dence of work absenteeism involving neck pain in acohort of claimants to the Ontario Workplace Safety& Insurance Board (WSIB).

The Context

Ontario Workplace Safety & Insurance BoardThe Ontario WSIB is a public insurance system legislatedby the Workplace Safety & Insurance Act to provideno-fault insurance for workplace injuries and diseases toOntario workers and workplaces.11 In 1998, approxi-mately 65% of Ontario workers were covered by theWSIB.

Two main types of coverage exist within the WSIB:“Schedule 1” and “Schedule 2.” Under “Schedule 1”coverage, employers are not individually liable to paybenefits directly to workers or their survivors. These em-ployers are required to submit a claim to the WSIB within3 days of a worker’s injury if the injury resulted in losttime from work, wage loss, or the worker receivinghealth care. Employers covered under “Schedule 2” arecompanies that do not pay premiums to the WSIB butare compulsorily covered through a system of individualliability (they are required to pay an administrative feewith each claim submitted—approximately 29% of thetotal injury costs). These companies include telephoneand telegraph companies, navigation companies, inter-national bridges, provincial government (includingboards, commissions, and Crown agencies), airlines witha regularly scheduled international passenger service,municipalities (including municipal boards and commis-sions, except hospital boards), public library boards, andschool boards. “Schedule 2” employers are required toreport all workplace injuries to the WSIB and they areresponsible to pay the total costs of benefits for theirinjured employees. In this article, all injuries reported by“Schedule 2” employers are aggregated under the rubric“Schedule 2.” Workers who are self-employed or em-ployed by companies that are not required to have WSIBcoverage are not required to report injuries to the WSIB.

Methods

Source Population and DesignThe source population included all injured workers 18 years ofage or older with an accepted lost-time claim to the WSIB in1998. Our design includes a cross-sectional and a prospectivecomponent. First, we measured the prevalence from a cross-sectional analysis of all injured workers with active lost-timeclaims in 1998. Second, we measured the incidence of lost-timeclaims involving neck pain by forming a historical cohort ofinjured workers with a new lost-time claim corresponding toinjuries that occurred between January 1 and December 31,1998. The incidence analysis only included claimants who didnot make a claim for neck pain in the year before their indexclaim. The study received ethics approval from the Universityof Toronto Ethics Review Board.

Definition of Neck PainWe aimed to measure neck pain related to soft-tissue disordersof the cervical spine/shoulder area including disc lesions andradiculopathy. The clinical presentation of neck pain may in-clude symptoms in the head, trapezius muscle, shoulder, upperback, upper arm and arm.13,14 We excluded neck pain associ-ated with fractures, tumors, infections, rheumatoid arthritis,mylopathies, lacerations to the neck–shoulder region, shouldertendinitis as well as dislocations and subluxations of the gleno-humeral joint.

Data Sources and Linkage

WSIB Claim Data File. We used the WSIB claim data file toidentify lost-time claims involving neck pain. This file includes(1) age; (2) sex; (3) date of accident; (4) injured part of body; (5)nature of injury; and (6) occupation.

Employer File. The employer file provides information aboutthe sector of activity of all firms registered with the WSIB. Thisdata were used to classify firms into 1 of 16 industrial sectors.

Data LinkageWe used firm numbers to deterministically link records fromthe claim data and employer files. The linked data file used foranalysis was stripped of all identifiers.

Enumeration and Validity of Neck-Pain ClaimantsWe used the “part of body” and “nature of injury” codes fromthe WSIB claim data file to identify injured workers with lost-time claims involving neck pain. The nature of the injury de-scribes the principal physical characteristics of the injury ordisease (e.g., sprains bruises, tendonitis). The part of body iden-tifies the worker’s anatomic location that was directly affectedby the nature of injury (e.g., cervical region/cervical vertebrae,multiple back regions). The methodology used to identify lost-time claimants is described in detail elsewhere.10

In summary, we reviewed all 610 nature of injury and 188part of body codes used by WSIB coders to code claims.10

These codes comply with the National Work Injuries Statisticscoding standards.15 We initially selected 60 nature of injuryand 27 part of body codes that may relate to neck pain andreached consensus on a final set of 173 code combinations. Wecombined these codes into 10 groups based on body regions(e.g., cervical region, back region). We then randomly selected434 claims for an in-depth chart review. Based on the availableinformation, the reviewer (D.V.E.) who was blind to the code

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combination determined whether a claimant had neck painaccording to the definition provided earlier.10

Our final set of body regions included 9 groups formed from60 nature of injury codes and 22 part of body codes. Theproportion of neck pain cases in each of the 9 final groupsvaried from 10% for the shoulder and head and face region to88% for the cervical region (Table 1). Twelve percent of thecervical region cases did not meet our criteria for soft-tissueinjuries of the neck and could be classified as false-positivecases (3 workers had back pain and 1 had a cervical disc her-niation with spinal cord compression). The back region groupincluded a significant proportion of neck pain cases (69%).

Estimation of the Population of Workers Covered bythe WSIB

We estimated the size of the population covered by the WSIBaccording to the method developed by Smith et al (2004) usingStatistic Canada’s Labor Force Survey (LFS)16,17. The LFS es-timates the working-age population in Canada (employed, un-employed, and nonlabor force participants) using a sample ofapproximately 54,000 Canadian households each month. Forour analysis, the LFS was restricted to “non-self-employed”labor force participants who were working in Ontario. Becauseof data availability, we restricted our analysis to workers whoare at least 20 years of age. We adjusted our estimates to ac-count for differences in mandatory coverage and reporting ofwork-related injuries to the WSIB among particular industrygroups in Ontario.5 To account for differences in hours of em-ployment between labor force participants (e.g., age and gen-der groups), we present all denominators as FTE. One FTEcorresponds to 2000 hours of work in 1 year (50 weeks � 40hours of work).

Analysis

Prevalence. We computed the cumulative, age-specific, gen-der-specific, and industrial sector-specific annual prevalence ofneck pain in lost-time claimants using 2 sets of denominators.First, we calculated the prevalence of neck pain as a proportionof all lost-time claimants. Second, we measured the prevalenceof neck pain as the proportion of all Ontario workers employedby firms with mandatory WSIB coverage using FTE’s (N1998 �2,819,437 FTE). Our numerator included one claim per year perclaimant, that is, claimants with multiple claims in a calendar yearwere only counted once.

Incidence. We computed the annual cumulative, age-specific, and gender-specific incidence of neck pain in lost-timeclaimants. We restricted this analysis to workers who made anew lost-time claim related to neck pain between January 1 andDecember 31, 1998. The incidence rate was calculated using

the total number of individuals employed by firms with man-datory WSIB coverage as the denominator.17 This denomina-tor does not represent a true population of workers at risk ofmaking a lost-time claim because it does not exclude workerswith prevalent lost-time claims involving neck pain. However,given the low prevalence of lost-time claims involving neckpain in the working population, we expect the resulting under-estimation of incidence to be minimal. As for prevalence, wedescribe the impact of selecting different WSIB code combina-tions on our estimates. All analyses were done using SAS Ver-sion 8.02 on a UNIX system.18

Assessment and Correction for “Hidden” Neck PainThe selection of “part of body” and “nature of injury” codesused to enumerate cases from WSIB claims data may influencethe measurement of prevalence.10 We used 2 numerators todescribe the impact of this bias. First, we used the number ofWSIB claimants with injuries coded with “part of body” and“nature of injury” codes referring to the cervical region only.As indicated by our validation study, 88.2% of claimantscoded as having an injury to the cervical region and neck havea soft-tissue disorder.10 Therefore, we weighted the first nu-merator by 0.882. Our second numerator was a weighted pro-portion of lost-time claimants with neck pain sampled fromall 9 groups derived from combinations of “part of body”and “nature of injury” codes10 (Table 1). These groups in-cluded the cranial region, neck region, shoulder, and upperarm with specific diagnoses, upper arm, back region, brain,trunk and multiple regions, face and head regions and mul-tiple body regions. For example, we found that 42.7% ofclaimants coded as “multiple body” injuries had neck pain.Therefore, our numerator included the total number ofclaimants with “multiple body” injury multiplied by 0.427.We adjusted the variance of the weighted prevalence andincidence estimates by using the variance (standard devia-tion) of the weight in the calculation of their 95% CI.

Results

Sample CharacteristicsWe estimated that the Ontario WSIB covered 2,819,437workers in 1998 (Table 2). Most of the Ontario work-force was younger than 49 years and almost 60% weremales. In 1998, 114,836 injured workers had active lost-time claims and received lost-time benefits (date of injurycould have been in 1998 or earlier, but the claim wasactive in 1998) (Table 2). The 3 industrial sectors withthe highest proportion of lost-time claimants are the ser-vice sector, the manufacturing sector, and “Schedule 2”employers (Table 2). These statistics cannot be used toinfer that these sectors are the most hazardous becausethey include the highest proportion of workers and aretherefore likely to include the highest proportion ofclaims.

Table 3 presents the characteristics of claimants codedwith disorders of the neck region and those coded withother code combinations from the 9 identified groups.Claimants coded with disorders of the neck region in-cluded a higher proportion of claimants in the 30 to 39years age-group and more women. We found no system-atic differences in the distribution of claimants acrossindustrial sectors.

Table 1. Proportion of Neck Cases by Injury Group10

Injury Group Proportion of Neck Cases

Neck region 0.882Back region 0.688Brain/concussion 0.550Multiple body 0.427Multiple face and body 0.350Upper arms 0.200Head 0.200Head, face 0.100Shoulder (specific diagnoses) 0.098

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Annual Prevalence of Work Absenteeism AssociatedNeck Pain in WSIB Lost-Time Claimants

When we relied on neck codes only, we found that 2.8%(95% CI 2.5–3.3) of claimants were off work each yearbecause of neck pain (Table 4). However, when we ac-counted for neck pain in workers coded with other inju-ries, the annual prevalence of neck pain increased to11.3% (95% CI 9.5–13.1). This 403% difference sug-gests that a significant amount of neck pain is hiddenwithin the classification system used to code claims.Because of this significant bias, we focus our descrip-tion of the burden of work absenteeism associatedneck pain to the figures obtained from all code combi-nations.

Of all claims with time-loss in 1998, 14.4% ofclaims by females and 10.1% of claims by males in-volved neck pain. We did not find that the annualprevalence varied across age groups (range, 10.4% in20 –29 year old group to 12.1% in 60 – 69 year oldgroup) (Table 4). When stratified by industrial sector,we found that lost-time claims involving neck painwere most common in the following sectors: healthcare (18.9%), Schedule 2 (14.3%), electrical (13.5%),

transportation (13.3%), and education (12.9%) (Ta-ble 5).

Annual Prevalence of Work Absenteeism AssociatedNeck Pain in Ontario Workers Covered by the WSIB

In Ontario in 1998, the annual prevalence of workabsenteeism involving neck pain was 30 per 10,000FTE (95% CI 25–34) (Table 6). Again, we observedthat using the neck codes only would lead to a largeunderestimation of the prevalence. Using the WSIBcovered population as a denominator, we found thatthe annual prevalence of work absenteeism involvingneck pain was higher in males (33 per 10,000 FTE)than females (24 per 10,000 FTE). This finding mayseem contradictory to our previous estimates. How-ever, it reflects the gender differences in the composi-tion of the denominators used to compute the annualprevalence; i.e., the male to female ratio is larger in thepopulation of WSIB lost-time claimants than it is inthe Ontario covered population (Table 2). The annualprevalence of neck pain peaked in the 30 to 39 year oldgroup (33 per 10,000 workers) and was the highest in30 to 39 year old males (38 per 10,000 FTE) (Table 6).

Table 2. Characteristics of Study Population in 1998*

Lost-Time Claimants,n (%)

Population Covered byWSIB, n (%)

N 114,836 2,819,437Age (yrs)

18–20 3035 (2.6) N/A20–29 25,124 (21.9) 706,216 (25.0)30–39 36,684 (31.9) 875,553 (31.1)40–49 29,773 (25.9) 743,186 (26.4)50–59 16,767 (14.6) 403,240 (14.3)60–69 3337 (2.9) 85,964 (3.0)70� 115 (0.1) 5278 (0.2)

GenderFemale 36,341 (31.6) 1,140,350 (40.4)Male 78,479 (68.3) 1,679,087 (59.6)

Industrial sector NAAgriculture 1897 (1.7)Automotive 8079 (7.0)Chemical/processing 2699 (2.4)Construction 7191 (6.3)Education 1289 (1.1)Electrical 539 (0.5)Food 4098 (3.6)Forest 1056 (0.9)Health care 8286 (7.2)Manufacturing 22,751 (19.8)Mining 758 (0.7)Municipal 1124 (1.0)Pulp and paper 418 (0.4)Schedule 2† 16,262 (14.2)Service 26,053 (22.7)Steel 2027 (1.8)Transportation 8933 (7.8)

*Missing data: age (1 claimant in lost-time claimants); gender (16 claimants inlost-time claimants); industrial sector (1376 claimants in lost-time claimants).†Schedule 2 includes railways, telephone and telegraph companies, naviga-tion companies, international bridges, provincial government (includingboards, commissions and Crown agencies), airlines with a regularly scheduledinternational passenger service, municipalities (including municipal boards andcommissions, except hospital boards), public library boards, police villages,and school boards.

Table 3. Unweighted Characteristics of 1998 Cohort ofInjured Workers*

Neck Pain Classification, n (%)

Neck Codes Only All Code Combinations†

N 3805 25,751Age (yrs)

18–20 37 (1.0) 395 (1.5)20–29 680 (17.9) 5017 (19.5)30–39 1423 (37.4) 8400 (32.6)40–49 1114 (29.3) 6978 (27.1)50–59 468 (12.3) 4057 (15.8)60–69 82 (2.2) 884 (3.4)70� 1 (0) 20 (0.1)

GenderFemale 1694 (44.5) 10,239 (39.8)Male 2111 (55.5) 15,504 (60.2)

Industrial sectorAgriculture 24 (0.6) 276 (1.1)Automotive 320 (8.4) 1943 (7.5)Chemical/processing 72 (1.9) 486 (1.9)Construction 140 (3.7) 1170 (4.5)Education 50 (1.3) 328 (1.3)Electrical 21 (0.6) 136 (0.5)Food 115 (3.0) 897 (3.5)Forest 34 (0.9) 182 (0.7)Health care 512 (13.5) 2927 (11.4)Manufacturing 546 (14.3) 4142 (16.1)Mining 21 (0.6) 136 (0.5)Municipal 34 (0.9) 250 (1.0)Pulp and paper 13 (0.3) 94 (0.4)Schedule 2 782 (20.6) 4511 (17.5)Service 690 (18.1) 5479 (21.3)Steel 45 (1.2) 347 (1.3)Transportation 372 (9.8) 2295 (8.9)

*Missing data: age (20 claimants in the all groups category); gender (8 claim-ants in the all groups category); industrial sector (14 claimants in the neck/cervical group and 152 claimants in the all groups category).†Injuries related to the cranial region, neck/cervical region, shoulder and upperarm with specific diagnoses, shoulder and upper arm with non-specific diag-noses, upper arm, back region, brain, trunk and multiple regions, face andhead regions, and multiple body regions.



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Annual Incidence of Work Absenteeism AssociatedNeck Pain in Ontario Workers Covered by the WSIB

In 1998, the annual incidence of work absenteeism asso-ciated neck pain in workers covered by the WSIB was 23

per 10,000 FTE (95% CI 20–27) (Table 7). Using claim-ants with neck codes only would have led to a 383%underestimation in the incidence. The incidence washigher in males (25 per 10,000 FTE; 95% CI 21–30) than

Table 4. Weighted Prevalence of Neck Pain in WSIBLost-Time Claimants in 1998

Neck Pain Classification, % (95% CI)

Neck Codes Only All Code Combinations*

Cumulative 2.8 (2.5–3.3) 11.3 (9.5–13.1)Gender-specific

Female 4.1 (3.6–4.6) 14.4 (12.3–16.4)Male 2.4 (2.1–2.7) 10.1 (8.4–11.8)

Age-specific20–29 2.4 (2.1–2.7) 10.4 (8.6–12.3)30–39 3.4 (3.0–3.8) 12.0 (10.1–13.9)40–49 3.3 (2.9–3.7) 12.0 (10.2–13.8)50–59 2.5 (2.2–2.8) 11.5 (9.7–13.2)60–69 2.1 (1.9–2.4) 12.1 (10.3–13.9)

Age- and gender-specificFemale

20–29 3.5 (3.1–3.9) 13.2 (11.1–15.3)30–39 4.9 (4.3–5.5) 15.1 (12.9–17.2)40–49 4.5 (4.0–5.1) 14.8 (12.7–16.8)50–59 3.2 (2.8–3.6) 14.4 (12.3–16.5)60–69 3.0 (2.6–3.4) 15.3 (13.1–17.5)

Male20–29 2.0 (1.7–2.2) 9.4 (7.7–11.2)30–39 2.8 (2.5–3.2) 10.7 (8.9–12.5)40–49 2.6 (2.3–3.0) 10.4 (8.8–12.1)50–59 2.0 (1.8–2.2) 9.7 (8.1–11.2)60–69 1.8 (1.6–2.0) 10.7 (9.1–12.3)

*Injuries related to the cranial region, neck/cervical region, shoulder and upperarm with specific diagnoses, shoulder and upper arm with nonspecific diag-noses, upper arm, back region, brain, trunk and multiple regions, face andhead regions, and multiple body regions.

Table 5. Weighted Industrial Sector-Specific Prevalenceof Neck Pain in WSIB Lost-Time Claimants in 1998

Industrial SectorNeck Codes

Only, % (95% CI)All Code Combinations,

% (95% CI)*

Agriculture 1.1 (1.0–1.3) 7.0 (5.7–8.2)Automotive 3.5 (3.1–3.9) 11.7 (9.9–13.4)Chemical/processing 2.4 (2.1–2.6) 9.1 (7.7–10.5)Construction 1.7 (1.5–1.9) 8.2 (6.9–9.5)Education 3.4 (3.0–3.8) 12.9 (11.1–14.8)Electrical 3.4 (3.0–3.9) 13.5 (11.2–15.7)Food 2.5 (2.2–2.8) 11.0 (9.2–12.7)Forest 2.8 (2.5–3.2) 8.8 (7.6–10.0)Health care 5.5 (4.8–6.1) 18.9 (15.9–21.9)Manufacturing 2.1 (1.9–2.4) 9.1 (7.6–10.6)Mining 2.4 (2.1–2.7) 9.3 (7.8–10.9)Municipal 2.7 (2.3–3.0) 11.2 (9.5–13.0)Pulp and paper 2.7 (2.4–3.1) 10.5 (8.9–12.1)Schedule 2† 4.2 (3.7–4.8) 14.3 (12.2–16.4)Service 2.3 (2.1–2.6) 10.7 (8.9–12.5)Steel 2.0 (1.7–2.2) 8.7 (7.2–10.2)Transportation 3.7 (3.2–4.1) 13.3 (11.3–15.4)

*Injuries related to the cranial region, neck/cervical region, shoulder and upperarm with specific diagnoses, shoulder and upper arm with nonspecific diag-noses, upper arm, back region, brain, trunk and multiple regions, face andhead regions, and multiple body regions.†Schedule 2 includes railways, telephone and telegraph companies, navigation com-panies, international bridges, provincial government (including boards, commissions,and Crown agencies), airlines with a regularly scheduled international passengerservice, municipalities (including municipal boards and commissions, except hospitalboards), public library boards, police villages, and school boards.

Table 6. Weighted Prevalence of Neck Pain (per 10,000;95% CI) in the WSIB Covered Population in 1998


Cumulative 7 (6–8) 30 (25–34)Gender-specific

Female 7 (6–8) 24 (21–28)Male 8 (7–9) 33 (27–39)

Age-specific20–29 6 (5–7) 27 (22–31)30–39 9 (8–10) 33 (28–39)40–49 8 (7–9) 29 (25–34)50–59 6 (5–7) 28 (24–32)60–69 5 (4–5) 30 (25–34)


20–29 5 (4–5) 18 (15–21)30–39 8 (7–9) 26 (22–29)40–49 8 (7–9) 27 (23–31)50–59 6 (6–7) 29 (25–33)60–69 4 (4–5) 25 (22–29)

Male20–29 7 (6–8) 33 (27–39)30–39 10 (8–11) 38 (32–45)40–49 8 (7–8) 30 (26–35)50–59 6 (5–6) 27 (23–31)60–69 5 (4–5) 32 (27–37)


Table 7. Weighted Incidence of Claims Involving NeckPain (per 10,000 Person–Year; 95% CI) in the WSIBCovered Population in 1998


Cumulative 6 (5–6) 23 (20–27)Gender-specific

Female 5 (5–6) 19 (16–21)Male 6 (5–7) 25 (21–30)

Age-specific20–29 5 (5–6) 24 (20–28)30–39 7 (6–8) 25 (21–29)40–49 5 (5–6) 21 (18–24)50–59 4 (3–4) 19 (16–22)60–69 3 (2–3) 18 (15–21)


20–29 4 (4–5) 16 (14–19)30–39 6 (5–7) 19 (17–22)40–49 6 (5–6) 20 (17–23)50–59 4 (4–5) 20 (18–23)60–69 3 (3–4) 15 (13–17)

Male20–29 6 (6–7) 29 (24–35)30–39 8 (7–9) 29 (24–34)40–49 5 (5–6) 22 (18–25)50–59 4 (3–4) 18 (15–21)60–69 2 (2–2) 20 (17–23)




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in females (19 per 10,000 FTE; 95% CI 16–21). Amongmale workers the incidence varied from 18 per 10,000FTE (95% CI 15–21) in the 50 to 59 year old group to 29per 10,000 FTE (95% CI 24–35) in those between theages of 20 to 39 years. In female workers, the incidencevaried from 15 per 10,000 FTE (95% CI 13–17) in 60 to69 year old age group to 20 per 10,000 FTE (95% CI17–23) in those between the ages of 40 and 59 years(Table 7).

Discussion

We conducted a cohort study to determine the preva-lence and incidence of work absenteeism involving neckpain in Ontario workers. Our study has 2 main findings.First, it provides evidence that neck pain is associatedwith a significant burden of disability in workers. Specif-ically, we found that 11.3% of Ontario workers whoreceived lost-time benefits in 1998 had neck pain associ-ated with their claim. Moreover, our analysis suggeststhat each year approximately 23 new cases of work ab-senteeism per 10,000 FTE’s will involve neck pain. Sec-ond, our analysis demonstrates that strictly relying onneck-specific codes such as those used by CanadianWorkers’ Compensation Boards can lead to a gross un-derestimation of the burden of neck pain in workers.Historically, North American Workers’ CompensationBoards have not considered neck pain to be a leadingsource of disability in workers; their statistics suggestedthat less than 5% of claims involved soft-tissue disordersof the neck.

The 2000 –2010 Bone and Joint Task Force onNeck Pain and its Associated Disorders accepted onlyone study describing the population-based incidenceof lost-time claims in workers. Silverstein et al6 re-ported that in Washington State, the annual incidenceof work absenteeism involving neck pain (off work formore than 4 days) was 19.1 per 10,000 FTE’s. Despitemethodological differences, we reported a similar in-cidence (23 per 10,000 FTE’s) in Ontario. There are 2main methodological differences between our studies.First, Silverstein et al only included primary injuries tothe neck in their numerator. In contrast, we accountedfor injured workers who had neck pain associated withother injuries.6 Second, we excluded workers who hada lost-time claim for neck pain in the previous yearwhereas the Washington estimates did not imposesuch restriction.

Our study has limitations. First, we likely under-enumerated all lost-time claims involving neck pain. Itis likely that the certain code combinations that wereomitted from our analyses included a small number ofinjured workers with neck pain. Second, we could notuse a “true” denominator of the workers at risk ofbeing off work because of neck pain. Although, thisbias led to an underestimation of our incidence esti-mates, it was likely minimal. The low number of prev-alent cases of work absenteeism because of neck painrelative to the size of the population covered by the

WSIB would not result in an important bias. Third, weestimated the prevalence and incidence of lost-timeclaims involving neck pain among Ontario workerscovered by the WSIB using FTE’s rather than workersas a denominator. FTE’s are based on the assumptionthat a full-time employee works 2000 hours per year(50 weeks � 40 hours per week). However, someworkers (e.g., part-time workers) work less whereasothers work more than 40 hours per week. Therefore,the number of FTE’s may not accurately reflect thenumber of workers covered by the WSIB. Finally, ourresults cannot be used to infer that neck disorders arethe sole cause of work absenteeism in workers withprevalent or incident neck pain. Rather, our analysisprovides us with crude figures of the association be-tween neck pain and lost-time claims. Future studiesshould focus on measuring the contribution of neckpain to an episode of work absenteeism in a cohort ofinjured workers with multiple injuries.

Conclusion

Our study highlights that neck pain is a disabling con-dition in workers. Traditional application of theworkers’ compensation statistics provide a gross un-derestimation of the burden of neck pain in workersdue to errors in the ways these claims are describedand coded. We believe that the collection of workers’compensation data could be improved to allow propersurveillance of neck pain in workers by allowing morethan one injury per claim to be recorded and by allow-ing diagnoses to change over time. Valid surveillanceof work-related disorders such as neck pain is essentialto measure secular trends in compensable injuries andto evaluate the impact of population-based preventionstrategies.

Key Points

● Little is known about the prevalence and inci-dence of neck pain in workers making lost-timeclaims to Workers’ Compensation Board.● We found that the prevalence and incidence ofneck pain in workers making lost-time claims var-ies considerably with the method used to ascertaincases.● The estimated percentage of lost-time claimantswith neck pain in 1998 ranged from 2.8% (95% CI2.5–3.3) using codes specific for neck pain to11.3% (95% CI 9.5–13.1) using a weighted esti-mate of codes capturing neck pain cases. The an-nual incidence of neck pain among the Ontarioworking population ranged from 6 per 10,000 FTE(95% CI 5–6) using only codes specific for neckpain to 23 per 10,000 FTE (95% CI 20–27) usinga weighted estimate of codes capturing neck paincases.



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● Male workers between the ages of 20 and 39years were the most likely to experience an episodeof work absenteeism involving neck pain.

References

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5. Workplace Safety & Insurance Board (WSIB). [Workplace Safety & Insur-ance Board (WSIB)]. 2005. Available at: http://www.wsib.on.ca/wsib/wsibobj.nsf/LookupFiles/DownloadableFile2005StatisticalSupplement/$File/2278A_StatSup.pdf.

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15. Association of Worker’s Compensation Boards of Canada. National WorkInjury/Disease and Fatality Statistics Program. Coder Reference Manual:Coding guidelines, issues and cases Version 2. [Association of Worker’sCompensation Boards of Canada.]. 1999;2.

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The Prevalence and Incidence of Work Absenteeism Involving Neck Pain