Activity Limitation in Rheumatoid ArthritisCorrelates With Reduced Grip Force Regardless ofSex: The Swedish TIRA ProjectINGRID THYBERG,1 URSULA A. M. HASS,2 ULLA NORDENSKIOLD,3 BJORN GERDLE,2 AND

THOMAS SKOGH4

Objective. To evaluate activity limitations 3 years after diagnosis of early rheumatoid arthritis (RA) in relation to gripforce and sex.Methods. A total of 217 patients, 153 women and 64 men, with recent-onset RA were included. Activity limitations werereported using the Health Assessment Questionnaire (HAQ) and the Evaluation of Daily Activities Questionnaire (EDAQ).The relationships between activity limitations versus grip force (measured by the Grippit), walking speed, functionalimpairment, grip ability, pain, plasma C-reactive protein, the 28-joint disease activity score and its components, thephysician’s global assessment of disease activity, and sex were analyzed by partial least squares (PLS).Results. Women had significantly lower grip force and more activity limitations (HAQ and EDAQ) than men. The PLSanalyses demonstrated that grip force was the strongest regressor of activity limitation, closely followed by walkingspeed. However, within subgroups based on grip force (group 1 � grip force <114 N, group 2 � 116–206 N, group 3 �214–321 N, group 4 � grip force >328 N) and including sexes, women and men had corresponding degrees of activitylimitation as reported by the HAQ and EDAQ.Conclusion. Our results indicate that the more pronounced activity limitations seen in women with RA, as comparedwith men, may be explained by lower grip force rather than sex.

KEY WORDS. Activity limitation; Grip force; Health Assessment Questionnaire; Evaluation of Daily Activities Question-naire; Rheumatoid arthritis; Sex.

INTRODUCTION

Rheumatoid arthritis (RA) is a chronic inflammatory dis-ease that ultimately leads to joint destruction and perma-

nent disability. However, early in the disease course, theinflammatory process leads to a multitude of functionallimitations (1–5). Several studies have also shown that RAis associated with a shortened life span, mainly due tocoronary vascular disease (6–8). Wolfe et al recently re-ported that patients’ self-assessed functional impairments,using the Health Assessment Questionnaire (HAQ), are thebest predictors of life expectancy compared with labora-tory, radiographic, and physical examination data (9).Early use of potent antirheumatic therapy is advocated toimprove the outcome (10).

Typically, disability in RA diminishes within the firstyear after diagnosis and start of intervention, and theneither remains stable but still affected (11) or slowly wors-ens over time (2,12). Two recent Swedish studies on earlyRA have found that women on average have more pro-nounced difficulties in performing daily activities thanmen as reflected by the HAQ (13,14). Apart from sex,factors such as age, disease activity, and joint destructionhave been found to correlate with HAQ score (4,15–18).Also, by using another instrument designed to evaluateactivity limitations in patients with RA, the Evaluation of

Supported by grants from the Medical Research Councilof Southeast Sweden, the National Board of Health andWelfare, the County Council of Ostergotland, the SwedishRheumatism Association, King Gustaf V 80-Year Founda-tion, and the Swedish Research Council (project K2003-74VX-14594-01A).

1Ingrid Thyberg, OT, MSc: The Swedish Institute for Dis-ability Research, Linkoping University, Linkoping, and Ore-bro Universities, Orebro, Sweden; 2Ursula A. M. Hass, PhD,Bjorn Gerdle, MD, PhD: Linkoping University, Linkoping,Sweden; 3Ulla Nordenskiold, OT, PhD: Institute of ClinicalNeuroscience, Sahlgrenska akademin, Goteborg University,Goteborg, Sweden; 4Thomas Skogh, MD, PhD: LinkopingUniversity, Linkoping, and Orebro University, Orebro, Swe-den.

Address correspondence to Ingrid Thyberg, OT, MSc,Rheumatology unit, Linkoping University Hospital, SE-58185 Linkoping, Sweden. E-mail: ingrid.thyberg@lio.se.

Submitted for publication February 13, 2005; accepted inrevised form June 27, 2005.

Arthritis & Rheumatism (Arthritis Care & Research)Vol. 53, No. 6, December 15, 2005, pp 886–896DOI 10.1002/art.21595© 2005, American College of Rheumatology

ORIGINAL ARTICLE

886

Daily Activities Questionnaire (EDAQ), women have beenfound to be more disabled than men (5,19). Similar tohealthy individuals, women with RA have a substantiallylower average grip force than men with RA (5,20–23).Several studies have also found that grip force is associ-ated with disability (5,20,24–26).

In a review of sex-based differences in patients with RA,Harrison pointed out the need for studies that highlightsex differences to optimize intervention strategies inwomen and men (27). The purpose of the present studywas to investigate possible differences between womenand men concerning grip force and activity limitation 3years after the diagnosis of recent-onset RA, and to deter-mine if activity limitation correlates with grip force.

PATIENTS AND METHODS

TIRA study. The present study is part of the Swedishearly intervention in RA (TIRA) project, in collaborationbetween 10 Swedish rheumatology units (Eskilstuna,Jonkoping, Kalmar, Lindesberg, Linkoping, Motala, Nor-rkoping, Oskarshamn, Vastervik, and Orebro) (13). A totalof 320 patients with recent-onset RA (�1 year after the firstself-reported signs of joint swelling) were included in theSwedish TIRA, 215 women (median age 56 years, inter-quartile range [IQR] 24) and 105 men (median age 62 years,IQR 20). The first signs of arthritis (joint swelling) wereobserved at least 6 weeks, but not more than 1 year, beforeinclusion. All patients either fulfilled at least 4 of 7 criteriafor RA as defined by the 1987 revised American College ofRheumatology (ACR) classification criteria (18) or experi-enced morning stiffness (�60 minutes as judged by thepatients), symmetric arthritis, and arthritis in small joints(fingers, hands, wrists, feet, and toes). The mean � SDnumber of ACR criteria was 4.5 � 0.8, with no differencesbetween women and men. The 44 patients who droppedout during the period from inclusion to the 3-year fol-lowup, 24 women (median age 69 years, IQR 23 at inclu-sion) and 20 men (median age 70 years, IQR 15 at inclu-sion), were significantly older (P � 0.001) than the rest ofthe study group. There were no significant differencesregarding the baseline Disease Activity Score in 28 joints(DAS28) (28) or HAQ score (29).

Study group. Of the 276 patients (86%) remaining inthe TIRA study at the 3-year followup, 191 (69%) werewomen (median age 55 years at inclusion, IQR 24) and 85(31%) were men (median age 60 years at inclusion, IQR20). Latex-agglutinating rheumatoid factor (RF) was ana-lyzed, and 62% of the women and 60% of the men were RFseropositive at the time of inclusion. The 217 (78%) pa-tients who completed the EDAQ (19) at the 3-year fol-lowup were included in the present study. Of these, 153(71%) were women (median age 56 years, IQR 24 at inclu-sion) and 64 (29%) were men (median age 60 years, IQR 21at inclusion). RF was present in 61% of the women and58% of the men at the time of inclusion. Of the 59 patientswho dropped out and did not complete the EDAQ, 37 werewomen (median age 50 years, IQR 27 at inclusion) and 22

were men (median age 59 years, IQR 23 at inclusion). Age,erythrocyte sedimentation rate (ESR), plasma C-reactiveprotein (CRP), DAS28 (28), grip force (21), and HAQ score(29) did not differ between the study group and the drop-outs, whereas the dropouts reported significantly moregeneral pain on a 0–100-mm visual analog scale (VAS)(P � 0.023) and more tender joints (P � 0.04).

The patients were offered medication and multiprofes-sional intervention when considered adequate, and ongo-ing medication was registered at followup. At the 3-yearfollowup, treatment with disease-modifying antirheumaticdrugs was ongoing in 65% of the women and 64% of themen. No differences were found between women and menregarding the proportion of patients who were prescribednonsteroidal antiinflammatory drugs, analgesics, or oralcorticosteroids.

Patient characteristics. ESR and CRP levels were ana-lyzed at the local hospital laboratories. DAS28 was calcu-lated (21) and the physician’s global assessment of diseaseactivity (PGA) was estimated on a 5-degree scale (range0–4, where 0 represents no activity and 4 represents highactivity). The patients estimated the duration of morningstiffness (minutes). Patients also graded average pain in-tensity and average wellbeing during the past week using0–100-mm VAS scales (where 0 represents no pain or bestpossible wellbeing and 100 represents worst possiblepain/wellbeing). Grip ability was tested using the GripAbility Test (GAT), which consists of 3 items; the score(range 10–276) is based on time consumption (high scoresindicating decreased hand function). The reliability andinternal consistency of the GAT are high (30). Signals ofFunctional Impairment (SOFI) was used to assess handfunction (4 items scored 0–16), upper limb function (3items scored 0–12), and lower limb function (4 itemsscored 0–16) (31). The scoring of each item ranged from 0(full function) to 2 (cannot perform) for the right and leftside, respectively. The reliability, validity, and sensitivityof SOFI have been reported to be adequate (31). Walkingspeed was defined as the time (seconds) it took to walk 20meters as fast as possible indoors; the patients used theirown assistive devices if necessary.

Grip force. Maximum, momentary, and average gripforce (N) over a period of 10 seconds were measured in theright and the left hand separately using a digital electronicdevice (Grippit; Detektor AB, Goteborg, Sweden) (21). Inthis study, the average grip force of 10 seconds in the righthand was used. Three percent of the patients were lefthanded, with no significant difference in grip force in theleft or right hand in comparison with the right-handedpatients.

Activity limitation. The Swedish version of the HAQ(29) was used to report difficulties in performing activities.The HAQ includes 20 items divided into 8 groups. TheHAQ score is achieved by adding the highest score withineach group divided by the number of completed groups,and ranges from 0 to 3 (where 0 � without any difficultyand 3 � unable to do). Difficulties performing daily activ-

Activity Limitation and Grip Force in RA 887

ities were also measured by the EDAQ, which consists of102 items grouped into 11 dimensions: eating/drinking,transfer, toileting, dressing, bathing, cooking, mobility in-doors, cleaning, washing/clothes care, mobility outdoors/shopping, and communication (19). Each dimension con-tains 4–13 items, which in this study are termed“activities.” Difficulties performing activities were repre-sented by the answer to the question, “How do you per-form the following activities without assistive devices oraltered methods?” The scale ranged from 0 to 3 (where 0 �without any difficulty and 3 � unable to do). The occupa-tional therapist gave instructions regarding the EDAQ atthe visit. The questionnaire was completed by the patientat home and was sent back within 2 weeks. An EDAQscore is calculated by adding the highest score within eachdimension and then by dividing by the number of com-pleted dimensions, and the score ranges from 0 to 3 (where0 � without any difficulty and 3 � unable to do).

Statistics. All statistics were calculated using SPSS forWindows version 11.5 (SPSS, Chicago, IL) or SIMCA-Pversion 10.0, and P values �0.05 were considered signifi-cant. Median values and IQRs are presented. The Kruskal-Wallis test was performed to determine if significant dif-ferences occurred between subgroups, and if so, the Mann-Whitney U test was used to test differences betweenindependent subgroups and to test differences betweenwomen and men. Partial least squares or projection tolatent structures (32) was used to investigate the relation-ships between variables representing patient characteris-tics and grip force versus variables representing activitylimitation. The variable influence on projection (VIP) pro-

vides information about the relevance of each X variableand each Y variable pooled over all dimensions, and VIP�1.0 is considered significant. Components with eigenval-ues �2.00 were considered nontrivial components. Multi-ple linear regression is an alternative method for the pre-diction, but it assumes that the regressors (X variables) aremathematically independent, and only 1 Y variable at atime can be predicted. If multicolinearity (high correla-tions) occurs among the X variables, the calculated regres-sion coefficients become unstable and their interpretabil-ity breaks down. Outliers were identified using the 2methods available: score plots in combination with Hotell-ing’s T2 (identifies strong outliers) and distance to modelin X space (identifies moderate outliers). Subgroups ofpatients, based on grip force (means), were identified byK-means cluster analysis. All data except EDAQ scorewere collected at the regular visit.

Ethics. All patients gave written informed consent toparticipate. The local ethics committees of the participat-ing units approved the protocol for the study.

RESULTS

Patient characteristics. The majority of the variablesdid not differ significantly between women and men inthe study group (Table 1). A small but significant differ-ence was found in SOFI assessments of the upper limb,where men had more functional impairment than women(Table 1).

Table 1. Comparison of patient characteristics, grip force, and activity limitationbetween women and men*

Variable Women (n � 153) Men (n � 64) P

Patient characteristicsESR, mm/hour 15 (20) 16 (26) NSCRP, mg/liter 5 (9) 5 (10) NSSwollen joints (range 0–28) 2 (5) 3 (7) NSTender joints (range 0–28) 2 (5) 1 (4) NSDAS28 score 3.45 (2.23) 3.42 (2.08) NSPGA (range 0–4) 1 (0.25) 1 (1) NSMorning stiffness, minutes 30 (55) 30 (87) NSPain (0–100-mm VAS) 30 (38) 26 (48) NSWellbeing (VAS, mm) 31 (36) 28 (49) NSGAT (range 0–276) 18 (9) 20 (9) NSSOFI hand (range 0–16) 1 (3) 2 (4) NSSOFI upper limb (range 0–12) 0 (1) 1 (3) � 0.001SOFI lower limb (range 0–16) 2 (3) 1 (2) NSWalking speed, seconds 13 (4) 12 (5) NS

Grip force and activity limitationGrip force, N 114 (104) 221 (154) � 0.001HAQ (range 0–3) 0.63 (1.0) 0.25 (0.75) � 0.001EDAQ (range 0–3) 0.66 (0.91) 0.29 (0.66) � 0.001

* The median missing rate in the variables was 4% (range 0–16%). Values are the median (interquartilerange) unless otherwise indicated. ESR � erythrocyte sedimentation rate; NS � not significant; CRP �C-reactive protein; DAS28 � disease activity score 28 joint count; PGA � physicians global assessment ofdisease activity; VAS � visual analog scale; GAT � Grip Ability Test; SOFI � Signals of FunctionalImpairment; HAQ � Health Assessment Questionnaire; EDAQ � Evaluation of Daily ActivitiesQuestionnaire.

888 Thyberg et al

Grip force. The mean � SD grip force in men (222 �108) was significantly higher than in women (126 � 74)(Table 1).

Activity limitation. On average, women had a signifi-cantly higher HAQ score than men (Table 1). Womenreported significantly more pronounced difficulties thanmen in 11 of the 20 activities in the HAQ, whereas in 9activities there were no differences (Table 2). Of the 20activities in the HAQ, 11 were mainly performed using theupper extremities (Table 2), and 6 (55%) of these 11 activ-ities were significantly more difficult for women to per-form compared with men. Of the other 9 HAQ activities,which were not mainly dependent on the upper extremi-ties, 5 activities (55%) were significantly more difficult forwomen to perform compared with men. The activitiesmost frequently reported as difficult to perform by bothwomen and men were “open jars which have been previ-ously opened” and “reach and get down a 5 pound objectsuch as a bag of sugar from just above your head.”

On average, women had a significantly higher EDAQscore than men (Table 1). Women stated significantly moremarked difficulties than men in 46 of the 102 activities inthe EDAQ; however, there were no differences in the re-maining 56 activities (Table 2). Of the 102 activities in theEDAQ, 77 were mainly performed using the upper extrem-ities, and in 39 (51%) of these activities, women hadsignificantly more difficulties than men (Table 3). Of theremaining 25 EDAQ activities, which were not mainlydependent on the upper extremities, 7 activities (28%)were significantly more difficult for women to perform

compared with men. The activities most frequently re-ported as difficult to perform by women belonged to thedimensions eating/drinking (“opening glass jar” and“opening juice bottle”), cooking (“lifting frying pan” and“reaching for sugar”), and activities related to mobilityoutdoors/shopping (“taking long walks,” “bringing homegroceries,” and “shopping on a large scale”) (Table 3). Formen, the most frequently reported difficulties were “open-ing glass jar” and “taking long walks.” For women, 71% ofthe 102 activities within the EDAQ were performed “with-out any difficulty,” and for men, 84% were performed“without any difficulty.”

Regression of activity limitation. Activity limitationsmeasured by HAQ and EDAQ scores were regressed by 16variables (Figure 1). Six of these variables were significantand entered into the model (grip force, walking speed,SOFI lower extremities, pain, wellbeing, and PGA) and theexplained variation (R2) was 0.55. When the HAQ scorealone was regressed by the 16 variables, the same 6 signif-icant variables were entered into the model (grip force [VIP1.57], walking speed [VIP 1.57], SOFI lower extremities[VIP 1.44], pain [VIP 1.28], wellbeing [VIP 1.09], and PGA[VIP 1.04]) and the explained variation (R2) was 0.61.When the EDAQ score alone was regressed by the 16variables, the same 6 significant variables were enteredinto the model, although grip force (VIP 1.54) changedplace with walking speed (VIP 1.6), and thereafter SOFIlower (VIP 1.47), pain (VIP 1.32), wellbeing (VIP 1.12), andPGA (VIP 1.03) were entered into the model and the ex-plained variation (R2) was 0.5.

Table 2. Percentage distribution in the Health Assessment Questionnaire (HAQ) in 20 items*

0 1 2 3HAQ items W (M) W (M) W (M) W (M) P

Shampoo your hair† 76 (85) 21 (15) 2 1 NSDress yourself including tying shoelaces and doing

buttons†53 (69) 42 (28) 5 (4) NS

Stand up from an armless straight chair 67 (74) 26 (26) 5 2 NSGet in and out of bed 75 (80) 22 (21) 3 NSCut your meat† 55 (80) 30 (19) 14 (2) 1 0.001Open a new milk carton† 82 (84) 15 (14) 4 (2) — NSLift a full glass to your mouth† 75 (89) 23 (9) 2 (2) — 0.045Climb up 5 steps 64 (82) 33 (19) 3 — 0.016Walk outdoors on flat ground 72 (83) 22 (15) 6 (2) — NSTake a tube bath 55 (71) 20 (27) 15 (2) 10 0.018Get on and off the toilet 74 (87) 18 (11) 8 (2) — 0.049Wash and dry your entire body† 69 (78) 30 (19) 2 (4) — NSReach and get down a 5 pound object such as a

bag of sugar from just above your head†42 (63) 43 (32) 1 (6) — 0.006

Bend down to pick up clothing from the floor† 68 (78) 26 (19) 5 (4) — NSOpen car doors† 72 (85) 23 (15) 5 — 0.045Open jars that have been previously opened† 28 (61) 39 (26) 31 (13) 2 � 0.001Turn faucets on and off† 65 (80) 26 (17) 9 (4) — 0.048Do chores such as vacuuming and yardwork 49 (83) 38 (17) 12 2 � 0.001Run errands and shop 50 (84) 31 (12) 18 (4) 2 � 0.001Get in and out of a car 62 (74) 31 (24) 7 (2) — NS

* Test between women (W) (n � 153) and men (M) (n � 64). P values �0.05 are considered significant. The median missing rate in items was 16%(range 15–51%). 0 � without any difficulty; 1 � with some difficulty; 2 � with much difficulty; 3 � unable to do; NS � not significant.† Activities mainly performed by using upper extremity.

Activity Limitation and Grip Force in RA 889

Table 3. Percentage distribution in Evaluation of Daily Activities Questionnaire in 102 activities grouped in 11 dimensions*

0 1 2 3

PW M W M W M W M

Eating/drinkingLifting glass† 80 91 20 8 2 NSLifting cup† 78 92 21 6 1 2 0.017Using knife, fork† 77 88 20 13 3 NSCutting bread† 54 76 41 22 5 2 0.002Slicing cheese† 56 71 38 25 6 3 0.034Bringing down milk carton† 67 86 29 14 4 0.003Pouring milk† 69 86 26 14 5 0.008Opening milk carton† 46 69 40 30 11 2 3 0.001Opening bottle† 49 78 35 22 13 3 � 0.001Opening glass jar† 20 52 46 38 24 6 11 4 � 0.001Opening juice bottle† 26 61 50 36 15 3 9 � 0.001Opening can† 42 68 39 27 13 5 7 � 0.001

ToiletingGetting to toilet 93 97 7 3 NSSitting on and rising from toilet 77 87 20 11 2 2 1 NSDrying oneself after toilet visit† 87 92 11 6 2 2 NSWashing back† 91 97 9 3 NSArranging clothes† 88 92 11 8 1 NSWashing hands† 96 98 4 2 NSBrushing and combing hair† 84 89 15 11 1 NSBrushing teeth† 87 95 13 5 NSUsing toothpaste† 83 89 17 11 1 NSUsing suppository† 90 90 9 10 1 NSOpening medicine bottle† 68 86 28 15 3 1 0.008Putting on makeup† 88 92 12 8 NSPutting on jewelery† 69 91 27 9 5 0.001

DressingOutdoor clothing† 78 87 21 13 1 NSClothes over head† 73 81 26 19 1 NSClothes with front button† 81 84 16 13 3 3 NSButtoning and unbuttoning† 68 76 29 21 3 3 NSClothes over feet† 72 78 27 21 1 NSZipping and unzipping† 78 92 21 8 1 0.013Putting on tights† 69 70 27 28 3 2 1 NSPutting on shoes† 78 75 19 24 3 2 NSPutting on boots† 69 74 24 26 7 1 NSTying shoelaces† 72 78 21 19 6 2 1 2 NSPutting on finger gloves† 83 93 14 7 3 0.044

Bathing/showerGetting to bathroom 95 97 5 3 1 NSGetting in and out of bathtub 54 66 27 26 6 6 12 2 NSStanding up to take a shower† 88 91 10 9 1 1 NSWashing neck and back† 61 73 31 22 5 5 3 NSDrying neck and back† 70 83 24 13 4 5 2 NSWashing and drying feet† 73 75 21 20 5 3 1 2 NSManaging lever† 80 94 17 6 3 1 0.009Washing hair† 80 89 16 11 2 2 NSPutting hair in rollers† 68 93 20 7 5 7 0.040Blow-drying hair† 74 90 18 10 3 4 NSManicure† 78 83 15 18 5 2 NSPedicure† 63 69 22 26 8 4 7 2 NS

CookingWalking into kitchen 92 97 7 3 1 1 NSWorking in kitchen 78 89 17 12 5 NSSetting the table† 88 97 11 3 1 0.049Peeling potatoes† 59 76 36 23 5 2 1 0.015Burning on stove† 77 92 18 8 4 1 0.010Lifting frying pan by its handle† 25 65 44 27 19 7 12 2 � 0.001Emptying potato water† 48 78 34 21 15 2 3 � 0.001

(continued)

890 Thyberg et al

Table 3. Percentage distribution in Evaluation of Daily Activities Questionnaire in 102 activities grouped in 11 dimensions*(Continued)

0 1 2 3

PW M W M W M W M

Reaching for sugar† 31 66 40 26 15 5 14 3 � 0.001Making sponge cake† 75 91 20 6 4 3 1 0.036Bread in and out of oven† 63 87 33 11 4 3 1 0.005Washing the dishes† 85 93 13 7 2 1 NSPicking up dishes† 70 87 26 12 3 2 1 0.011

Mobility indoorsWalking indoors 88 95 11 5 1 1 NSOpening outer door† 83 95 16 1 1 0.015Opening yale lock† 78 91 20 10 2 1 0.026Answering the door 86 95 12 3 1 2 1 NSOpening balcony door† 84 93 14 7 1 1 NSWalking out on balcony 92 97 6 3 1 1 NSGetting to the telephone 83 92 16 6 1 1 NS

CleaningMaking the bed† 68 73 27 26 3 2 2 NSDusting† 83 96 14 2 1 2 1 0.019Sweeping the floor 76 88 17 11 5 3 NSCleaning kitchen floor 63 78 25 17 9 5 3 0.034Wringing out cloth† 46 63 40 31 11 7 3 0.020Using vacuum cleaner 53 79 30 19 14 2 3 � 0.001Opening window† 73 90 21 8 5 2 1 0.006

Washing clothes careWashing up in bowl† 79 90 16 1 5 NSPutting wash in machine† 89 98 6 2 1 3 NSHanging up wash† 67 87 24 11 6 2 3 0.004Ironing blouse† 77 85 19 12 3 2 2 NSTurning up hem of a skirt† 70 87 19 9 7 4 5 NSCutting out material† 61 89 27 4 10 4 2 4 0.008Picking up needles† 55 70 37 23 7 6 1 NSPutting in and taking out plug† 63 85 28 15 7 1 0.002Opening/folding ironing board† 66 92 24 8 6 4 � 0.001

TransferringGetting into bed 92 95 8 5 NSTurning in bed 78 79 20 21 2 NSGetting out of bed 80 81 19 19 1 1 NSRising from chair 77 81 18 19 3 2 NS

CommunicationUsing telephone† 92 98 8 2 NSHolding a bock† 72 89 25 10 3 2 0.009Writing a postcard† 83 93 13 7 3 1 NSTaking out money† 81 92 15 8 3 0.044

Mobility outdoors/shoppingWalking on flat ground 82 92 13 9 4 1 NSTalking long walks 43 48 36 44 11 9 11 NSWalking up stairs 50 66 30 29 14 3 6 2 0.017Going by tram/bus 77 89 15 10 3 2 5 NSGetting in and out of car 63 78 32 22 4 1 0.024Driving a car† 81 93 14 7 1 4 0.031Opening entrance doors† 69 93 25 7 5 1 � 0.001Opening elevator door† 73 97 22 4 4 11 � 0.001Walking to the shops 75 89 18 11 4 4 0.016Bringing home groceries 30 58 52 40 10 2 9 � 0.001Shopping on a large scale 30 61 41 33 9 5 20 � 0.001

* Test between women (W) (n � 153) and men (M) (n � 64). P values �0.05 are considered significant. The median missing rate in the activities was2% (range 0–48%). 0 � without any difficulty; 1 � with some difficulty; 2 � with much difficulty; 3 � unable to do; NS � not significant.† Activities mainly performed by using upper extremity.

Activity Limitation and Grip Force in RA 891

Correlation between activity limitation and grip force.The absolute average grip force for the study group corre-lated strongly and negatively with both the HAQ score(Spearman’s correlation coefficient � –0.632, P � 0.01)and the EDAQ score (Spearman’s correlation coefficient �–0.635, P � 0.01). The HAQ score was missing in 4 of the209 patients.

Dividing patients into subgroups based on grip force. Intotal, 209 of the 217 patients could be divided into 4subgroups based on the mean grip force values over 10seconds (Table 4). Grip force values were missing in 8patients. Subgroup 1 included the 88 patients with thelowest grip force (�114 N), where women were in themajority. Subgroup 2 (116–206 N) included 71 patients,again with women in the majority. Subgroup 3 (214–321N) included the 19 women with the highest grip force and19 men. Finally, subgroup 4 (�328 N) included 12 menwith the highest grip force (Table 4). The median age wassimilar in subgroups 1 and 4, and the lowest median agewas found in subgroup 3 (Table 4).

Differences between subgroups. Grip force measure-ment revealed significant differences when comparingsubgroups (P � 0.001 for all comparisons). There were

significant differences in both HAQ score and EDAQ scorebetween subgroup 1 and subgroups 2, 3, and 4, and be-tween subgroups 2 and 3, whereas there was no significantdifference between subgroups 3 and 4 (Table 5).

Separate analysis of women and men revealed, in bothinstances, significant differences between subgroups con-cerning grip force (P � 0.001 for all comparisons) (Figure1). In the women, there were significant differences regard-ing EDAQ and HAQ scores between subgroups 1 and 2, 1and 3, and 2 and 3. In the men, there were also significantdifferences between all subgroups regarding EDAQ andHAQ scores, apart from EDAQ and HAQ comparisonsbetween subgroups 3 and 4 (Table 5).

When testing for differences in patient characteristicsbetween subgroups, 2 variables, the number of swollenjoints and SOFI upper limb, did not differ significantlybetween subgroups (Table 5). The majority of the patientcharacteristics differed significantly between subgroups 1versus 2 and between 1 versus 3. Differences betweensubgroups 2 and 3 were seen concerning some variables.The only difference between subgroups 2 and 4 concernedwalking time, whereas no differences were found betweensubgroups 3 and 4 (Table 5). Therefore, the women andmen in subgroup 1, having a mean grip force �114 N, hadhigher disease activity and more pronounced disabilitycompared with the women and men in subgroup 2, with agrip force between 116 and 206 N. At the same time,women and men in subgroup 2, with a grip force between116 and 206 N, did not differ significantly regarding pa-tient characteristics compared with the men in subgroup 4,with a grip force �328 N, although the men in subgroup 4had significantly more pronounced activity limitations.The women and men in subgroup 3, with a grip force of214–321 N, did not differ significantly regarding any vari-ables (except the grouping variable grip force).

Differences within subgroups. The mean grip force andthe median HAQ score for women and men distributed inthe 4 subgroups are shown in Figure 2A, and the mean gripforce and the median EDAQ score are shown in Figure 2B.Within subgroups 1, 2, and 3, where women and men weregrouped together according to the absolute grip force, therewere no significant differences between women and menregarding difficulties in performing activities as judged byHAQ or EDAQ scores (Figure 2).

Of the 122 activities/items in the EDAQ and HAQ, 110(90%) did not differ between women and men within the

Figure 1. Partial least squares regression of the Health Assess-ment Questionnaire and the Evaluation of Daily Activities Ques-tionnaire (Y variables) using the patient characteristics variablesand grip force as regressors (X variables). Variable influence ofprojection (VIP) is given for each variable. Values �1.0 are con-sidered significant, and significant variables are shown in bold.The explained variance (R2) is 0.50. SOFI � Signals of FunctionalImpairment; PGA � physicians global assessment of disease ac-tivity; ESR � erythrocyte sedimentation rate; CRP � C-reactiveprotein; GAT � Grip Ability Test.

Table 4. Patient subgroups by grip force

Subgroup*

Total patients (n � 209) Women (n � 148) Men (n � 61)

AgeNo.; median (range)

AgeNo.; median (range)

Grip forceMean; median (range)

AgeNo.; median (range)

Grip forceMean; median (range)

66; 66 (5–114) 13; 51 (27–80) 81; 85 (39–110)1 88; 59 (27–81) 75; 59 (35–81) 159; 157 (116–206) 17; 59 (18–76) 169; 173 (134–201)2 71; 56 (19–76) 54; 55 (19–76) 262; 259 (214–312) 19; 65 (31–74) 264; 263 (221–321)3 38; 54 (18–75) 19; 37 (18–75) — 12; 59 (29–69) 384; 387 (328–488)4 12; 59 (29–69) —

* Grip force in Newtons: 1 � �114; 2 � 116–206; 3 � 214–321; 4 � �328.

892 Thyberg et al

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ubg

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(n�

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bgro

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ubg

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(n�

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(ran

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ange

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AQ

(ran

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75(1

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13(0

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0.0

(0.0

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0.00

10.

043

0.00

20.

001

0.04

90.

003

NS

ED

AQ

(ran

ge0–

3)1.

0(0

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0.58

(0.7

5)0.

16(0

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0.12

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10.

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10.

001

0.00

20.

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NS

Wom

enan

dm

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70(4

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1)26

2(4

8)38

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3)�

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0.0

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ange

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0.91

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001

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rist

ics

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mm

20(3

1)15

(21)

12(1

2)14

(18)

0.00

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025

NS

NS

NS

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CR

P,

mg/

lite

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(15)

5(8

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5(5

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029

NS

0.02

70.

038

NS

NS

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Sw

olle

njo

ints

(ran

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28)

3(9

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(4)

1(5

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(7)

NS

——

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der

join

ts(r

ange

0–28

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(7)

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0.00

10.

014

�0.

001

NS

0.00

1N

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(ran

ge0–

4)1

(1)

1(1

)1

(1)

1(1

.25)

�0.

001

�0.

001

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001

NS

0.02

6N

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orn

ing

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001

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ain

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001

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50.

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17(3

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(18)

�0.

001

0.00

4�

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001

NS

NS

NS

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han

d(r

ang

0–16

)2

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1(2

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(1)

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10.

042

NS

NS

NS

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up

per

lim

b(r

ange

0–12

)0

(2)

0(2

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(1)

1(3

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80.

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90.

010

NS

NS

Wal

kin

gsp

eed

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con

ds

14(6

)12

(4)

10(3

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10.

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40.

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Activity Limitation and Grip Force in RA 893

3 subgroups (data not presented). However, differenceswere found in 12 activities (8 in the EDAQ and 4 in theHAQ). In subgroup 1, women had significantly more pro-nounced difficulties in 2 activities in the EDAQ, i.e., open-ing a glass jar (P � 0.001) and opening a juice bottle (P �0.004), and in 2 activities in the HAQ, i.e., getting in andout of a bed (P � 0.02) and opening jars (P � 0.009). Menhad significantly more pronounced difficulties in 2 activ-ities in the EDAQ, i.e., getting to the bathroom (P � 0.045)and turning in bed (P � 0.004). In subgroup 2, women hadsignificantly more pronounced difficulties in 3 activities inthe EDAQ, i.e., emptying potato water (P � 0.032), openinga bottle (P � 0.020), and using a vacuum cleaner (P �0.048), and in 1 activity in the HAQ, i.e., vacuuming (P �0.02). In subgroup 3, women had significantly more pro-nounced difficulties, as assessed by the EDAQ, concerningthe lifting of a frying pan by its handle (P � 0.002),whereas men in subgroup 3 had significantly more diffi-culty, according to the EDAQ, buttoning and unbuttoning(P � 0.032).

Within the subgroups, men generally displayed signs ofmore pronounced inflammation than women. Therefore,within subgroup 1, men had a significantly more elevatedESR than women (P � 0.033), and within subgroup 2, menhad a significantly higher number of swollen joints (P �0.015) and pain (P � 0.034) than women. Furthermore,PGA (P � 0.01), GAT (P � 0.004), SOFI hand (P � 0.001),and SOFI upper extremity (P � 0.001) were more affectedin men in subgroup 2. In subgroup 3, men had a signifi-cantly higher DAS28 (P � 0.025). In addition, GAT (P �0.004), SOFI hand (P � 0.009), and walking speed (P �

0.029) were more affected compared with women in sub-group 3. Women in subgroup 3 were substantially youngerthan the men, whereas the opposite was found in sub-group 1.

DISCUSSION

In the present study, we investigated the relationship be-tween grip force and difficulty performing activities as-sessed by the HAQ and EDAQ. The HAQ was used on aroutine basis at all followups. The EDAQ was used at 3visits to identify difficulties in performing daily activitieswith the intention to facilitate planning and to evaluate theeffects of assisstive devices (5). On average, the HAQ aswell as the EDAQ, which both include many activities thatare dependent on the upper extremities, revealed morepronounced difficulties for women. Using regression ana-lysis, we found that grip force was the strongest regressorwhen HAQ and EDAQ were analyzed together. Also, whenwe regressed HAQ separately, grip force was the strongestregressor, closely followed by walking speed, SOFI lowerextremity, and pain. The same regressors were significantwhen EDAQ was regressed separately, although here walk-ing speed was strongest, closely followed by grip force.Sex and age were not identified as significant regressors ofHAQ and EDAQ. The degree of activity limitation, as mea-sured by the HAQ and the EDAQ, was associated with gripforce. Therefore, we found that both women and men withlow average grip force (�114 N) had substantial activitylimitations, indicating a need for multiprofessional inter-vention. Conversely, women and men with a grip forcecorresponding to that of healthy women (�214 N) (33) hadvery low HAQ scores. Our results regarding the relation-ship between activity limitation and grip force corroboratethe results of a recently published study where increasedvalues in performance-based functional measures (gripstrength, timed button test, and walking velocity) dis-played a proportional increase in self-reported disability(34).

The finding of lower grip force values in women withRA, as compared with men with RA, is not surprisingbecause this is also the case in healthy individuals.Women and men with RA had approximately the samerelative degree of grip force reduction, resulting in gripforce values of men comparable with those of healthywomen in most cases. Because many of the functionalabilities assessed by the HAQ and EDAQ require stronghands, it is not surprising that women with RA on averageproved to be more affected than men by means of theseinstruments. However, when women and men with RAwere subgrouped together with regard to grip force, itbecame evident that poor outcome assessed by the HAQand EDAQ was related to low grip force, but not to sex (orage) per se. The activity limitations seen 3 years after thediagnosis of RA were of approximately the same magni-tude as those seen after 1 and 2 years in both women andmen (5). Several investigators, using the HAQ, have re-ported more pronounced activity limitations in womenthan men (2,4,13–15,18,35), and this finding, together witha majority of other self-reported outcome measures, has

Figure 2. Top, Health Assessment Questionnaire (HAQ) scoresand number of women and men within subgroups. Bottom, Eval-uation of Daily Activities Questionnaire (EDAQ) scores and num-ber of women and men within subgroups.

894 Thyberg et al

been considered an indication of a more severe diseasecourse in women (16). The HAQ score has also been foundto increase with increasing age in patients with RA as wellas in healthy individuals (35), and Kuiper et al have ar-gued that the postmenopausal state may be responsible forthe difference in outcome between women and men (17).As judged by our results, however, grip force under orabove a critical level, rather than sex, age, or postmeno-pausal state, may be the most important explanation toactivity limitation. Therefore, women and men with com-parable grip force values also had comparable outcomemeasures by means of the HAQ and EDAQ. Interestingly,however, when women and men were subgrouped accord-ing to grip force, the men appeared to be more severelyaffected with regard to measures of systemic inflammation.

In line with our findings, Krishnan et al recently re-ported that there were no significant differences in theHAQ score between women and men in a general popula-tion in Finland with a mean age of 55 years (33). However,besides differences in grip force, HAQ score, and EDAQscore in our cohort, there was a small but significant dif-ference in SOFI upper limb, where men had higher scoresindicating more functional impairment. This small differ-ence is also seen in a Swedish reference population, whichis age and sex matched to the TIRA cohort (unpublishedobservations), indicating that this difference is dependenton sex.

Grip force and walking speed from inclusion through1-year followup in the Swedish TIRA cohort were alsofound to be significant regressors of self-reported variables(36). Compared with a healthy Swedish reference popula-tion (21), the grip force reduction in patients with RA witha disease duration of 12 years was �75% in women. Men,having approximately double the average grip force ofwomen, end up with a normal female grip force after a50% reduction. Therefore, the 50% grip force reduction inpatients with RA, as seen in both women and men in thisstudy, could be expected to have less impact on the HAQand EDAQ outcomes in men. The common observationthat women have a more severe form of RA than men couldpossibly, at least in part, be misleading due to the female-biased design of the HAQ and EDAQ, which to a greatextent evaluate traditional female activities. However,Wolfe et al reported that HAQ score is an even betterpredictor of life expectancy in men than in women (9).After subdividing RA patients into 4 groups with respectto absolute values of grip force, the sex differences con-cerning HAQ and EDAQ outcomes disappeared. This,however, does not exclude that grip force/hand functionand other functional abilities may also be associated withdisease activity (12). Our findings highlight the fact thatthe HAQ score in a study group is dependent on thepercentage distribution of women and men, respectively.This needs to be taken into consideration when comparingHAQ scores between study groups with different distribu-tions of female and male patients.

Several studies have reported that grip force increases asa result of interventions (30,37–42). The results in thepresent study also indicate that increasing the grip forcemay result in reduced activity limitations. However, fur-ther studies are needed to evaluate interventions directed

to reduce disabilities and to analyze the relationships be-tween different aspects of disability.

In conclusion, activity limitations are closely related togrip force, followed by walking speed and SOFI lowerextremity, regardless of sex. By grouping patients withrespect to grip force, we found that men and women withsimilar grip force had equal degrees of self-reported activ-ity limitation. This finding offers an explanation as to whywomen report more pronounced activity limitation thanmen. Therefore, low grip force is closely related to activitylimitation regardless of sex. At the same time, we foundthat subgroups of patients with low or no activity limita-tion had an average grip force corresponding to the averagegrip force of healthy women. In clinical practice, grip forcemeasurement is simple and rapidly performed, and theabsolute grip force can be used as an indicator to identifypatients with activity limitations and a need for multipro-fessional intervention.

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