American Journal of Industrial Medicine 2 2 8 7 W W (1992)

Upper Extremity Symptoms in Supermarket Workers Philip Harber, MD, MPH, Laura Peiia, Gerard Bland, BA, and John Beck, BS

Upper extremity symptoms in supermarket workers, particularly those who performed checking using laser scanners, were evaluated using a questionnaire administered by trained interviewers to 124 supermarket workers. Summary indices of exposure (shortterm and long-term) as well as indices of past personal illnesses and personal activities were employed. Outcome data were summarized by four composite symptom indices. Chi square and logistic regression analyses demonstrated that hours of checking work in the preceding 2 weeks and cumulative weighted years of work were associated with adverse upper extremity symptoms. Symptoms involved both the proximal and distal parts of the upper extremities. 0 1992 Wiley-Liss, Inc. Key words: repetitive motion syndrome, ergonomics, supermarket workers, upper extremity impairment, carpal tunnel syndrome, cumulative trauma disorders, arm

INTRODUCTION

Disorders due to repetitive motion have been increasingly recognized over the past several years. Supermarket checkers have been suspected as being at elevated risk of cumulative trauma disorders of the upper extremity [Barnhart and Rosenstock, 1987; Margolis and Kraus, 1987; Tyan, 19891. Technologic advances may have increased rather than decreased the risk. Specifically, substitution of laser scanners for manual keying operations has been suspected of increasing the risk by increasing the number of items checked and decreasing the diversity of work activities. This may have resulted from the increased work pace and task specialization. To address these concerns, the UCLA Occupational Medicine Branch, the United Food and Commercial Workers (UFCW Local 770), and the management of a California supermarket chain have initiated a research project to identify the risk factors and assess the efficacy of several interventions designed to decrease the risk. This report summarizes the results of the cross-sectional prevalence symptom survey performed in the initial phase of the project. These analyses were performed to determine if upper extremity symptoms were related to the extent of checking work performed, considering both recent work history and cumulative exposure to such work.

The Occupational Medicine BrancWDepattment of Medicine, University of California, Los Angeles. Address reprint requests to Philip Harber, M.D., M.P.H., Department of Medicine, University of California, Los Angeles, CA 90024-7027. Accepted for publication February 20, 1992.

0 1992 Wiley-Liss, Inc.

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TABLE 1. Population Characteristics in Study of Supermarket Workers All categories Age (years) Mean Standard deviation Minimum Maximum Female (%) Years working at store Mean Standard deviation Minimum Maximum Race (%) White Black Hispanic Other Total sample

Checkers

75ers

Clerks

Other

30.04 9.66 18 57 69(56)

32.45 10.39 19 54 33(69)

25.89 7.36 19 40

26.94 9.24 18 57 18(53)

30.94 6.24 21

6.75 6. I5 I 28

8.69 6.50

2.78 2.30

7(78)

1

1

28

9

5.18 5.94 I 23

54 1 l(33)

6.56 5.51 1

22

1(2) 30(63) 17(35)

2(6) 19(58) I2(36) -

48

33

METHODS

The study design was developed and implemented by a joint union-management-academic team. The protocol was reviewed and approved by the UCLA Human Subject Protection Committee, and each participant provided written informed consent to participate. All participating stores are owned by the same company and are located in the Los Angeles area. All nonmanagement employees received a letter (by mail and worksite distribution) describing the study and requesting participation; it emphasized the particular importance of participation of those who do checking work. Characteristics of participants are seen in Table I. Interviewing was performed before or after the scheduled work shift. The interviews were performed during summer and early fall, and some subjects were unavailable because of vacations at the time interviews were performed. Approxiniately 75% of available workers whose jobs involved checking participated. Participation rates were lower for those who did no checking work. Only limited demographic data are available for nonparticipants. Gender, as determined by first name, was similar (female = 55% of all employees, 56% of all participants, and 69% of participating checkers). Following worksite visits by the investigative team, including ergonomic consultants (Donald Bloswick, Ph.D., and Daniel Baker, M.S., Department of Mechanical Engineering, University of Utah), and discussions with union and management personnel, several job categories were established based upon the consensus about frequency of checking work. Checkers work predominantly in checkout operations. Seventy-fivers (“75ers”) are employees who do both checking and other grocery duties; they are generally “apprentice checkers” who have not yet been promoted to “checker.” Clerks include “courtesy clerks” who serve in bagging operations at the checkstand and assist customers by carrying bags to vehicles; and, in addition, “grocery clerks” who stock shelves. The “other” group includes all other trades.

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TABLE 11. Question Groups in Study of Surpermarket Workers Identification Medical history “Have you ever been told by a doctor that you have . . . rheumatoid arthritis?” Anatomic areaa: define area verbally and by diagram “Ever” diagnoses “Have you ever had a strain or strain involving these parts?’’ “How were you treated?” (four choices) “2 Week recall” “Have you had pain or discomfort in these areas in the past 2 weeks?” “On how many days over the last 2 weeks did the pain affect you this way?” Take medicine Miss work etc. “2 Year recall”: similar to above CTS-specific “Have you ever had a persistent feeling of weakness in your hand or fingers, such as difficulty with” Turning a key in a lock? Turning a doorknob? Dropping things or tools? “ . . . Have you had recurring hand, wrist, or finger problems such as . . . burning?’ Personal risk factors Chemical exposure Previous jobs Hobbies Work history at supermarket “XXX” “When did you first work for XXX?” “Over the past 2 weeks, how many hours did you” Work as a checker‘? Work as a grocery clerk? etc. Phalen’s test Interviewer asks subject to flex for 30 seconds and asks about subject’s pain “All: “Neck, shoulder, arms, elbows, wrists, hand, and fingers”; Proximal: “Neck, shoulder, upper arm, forearm, or elbow”; Distal: “Hand, wrist, or finger”. In addition, subjects completed anatomic drawings to show areas involved.

Although most checking was done by checkers, there was considerable overlap in work actually performed; checkers, “75ers,” and even managers also performed some checking work. Furthermore, the majority of the workers performing checking work had work schedules other than a standard 40 hour week. Most worked less than 40 hours per week, and hours per day varied. Trained interviewers conducted standardized interviews in privacy. The interview schedule included questions about personal characteristics, relevant medical history (e.g., history of acromegaly, pregnancies), and history of medication use. In addition, it included a complete occupational history; special questions addressed chemical exposures and jobs considered to have a high frequency of repetitive wrist motions. Specific questions addressed any previous traumatic injury to the upper extremities or symptoms requiring medical attention. Table I1 summarizes general categories of questions and provides examples of questions. Questions were asked about three different anatomic regions.

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Questions about the entire upper extremity (defined as “neck, shoulder, arms, wrists, hands, and fingers”) were also asked. To facilitate understanding of the definitions, workers were shown anatomic torso drawings with these areas highlighted. Three recall periods for symptom questions were utilized. First, “Have you ever had a strain or sprain . . . ?” Second, “In the past 2 weeks have you had pain or discomfort . . . ?” Third, “In the past 2 years have you had recurring problems such as . . . ?” Responses regarding specific symptoms were requested (burning, stiffness, pain, cramping, tingling, numbness, swelling, other . . . ). For clarity, subjects were shown anatomic drawings to emphasize the specific area in question. For several of the questions, the subject was asked to shade areas of anatomic drawings which corresponded to the discomfort reported. Additional questions focused on specific functional symptoms (e.g., “Do you have difficulty turning a doorknob?”). Several types of questions were used to assess exposure to possible occupational risk factors. Questions focused on previous jobs, including specific ‘‘high risk” occupations, and personal activities. Other questions focused specifically upon work at this supermarket chain. Each job held was listed. Other questions specifically addressed work during the preceding two weeks, including total hours, and hours worked as a checker, grocery clerk, doing stocking work, and other work. A limited Phalen’s test was performed, recording if the subject reported pain in “distal” areas. The questionnaire is available from the authors. To facilitate meaningful analysis about the frequency of symptoms and the relationships between exposure and symptoms, composite indices were developed to aggregate data. The composite indices were designed prior to performing the formal statistical analysis in order to avoid potential biases. The combined indices are summarized in Table 111. They fall into three categories: personal factors, exposure factors, and symptoms. Data management was carried out using Dbase programs (Ashton-Tate, Torrance, CA), and statistical analyses were performed using BMDP [Dixon, 19831. For simple analysis of categorical variables, chi square testing was performed. For more complex multivariate analyses, logistic regression was employed for dichotomous outcome variables. Stepwise forward algorithms by maximum likelihood estimation were utilized [Engelman, 19831. A p value less than 0.05 was considered to be significant, and between 0.05 and 0.10 to be of possible significance. The available questionnaire data did not permit establishing clinical diagnoses (e.g., carpal tunnel syndrome [CTS], lateral epicondylitis). Furthermore, the distributions of responses to symptom questions were not bimodal (which would have suggested a clear basis for separation of “diseased” and “healthy” subjects). Therefore, the decision was made a priori to separate outcome indices at the upper quartile vs. the remaining three quartile levels (quartile, Q). Several exposure indices were used: for job title (E-JOB), checkers were in the most “exposed” category, clerks and 75ers in an intermediate category, and all other workers were in the least exposed category. To assess short-term effects on symptoms, work hours on the day of interview (E-WHR) were included as a possible explanatory variable. Checking hours over the past 2 weeks (E-CHR) expressed the estimated number of hours spent performing checking work during the 2 weeks immediately prior to the date of interview. Weighted exposure (risk) years (E-RYR) was based upon the total number of months working in the supermarket; a weight was assigned to each month of employment according to an a priori scheme (full time

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TABLE 111. Composite Indices in Study of Supermarket Workers* Points

Type

Question(s)

Personal factor indices P-ILL

-

Any of list of medical problems Any prior history of a d h a n d diagnosis “Ever” cast or fracture

Ever Ever Ever

Chemical exposures Selected hobbiesljobs (e.g., butcher, knitting) Jobs involving repetitive hand/adwrist motion

Ever 2 year 2 year 2 year Ever Ever Ever Ever

Recurrent symptoms From list of symptoms Burn, tingle, pain Pain awakening from sleep Difficulty turning lock Difficulty with knob Difficulty holding things. . Change job due to. . . .

Ever Ever Ever 2 year 2 year 2 weeks Ever

Sprain or strain Recurrent lower arm symptoms Recurrent upper arm symptoms Recurrent distal symptoms Recurrent proximal symptoms Pain/discomfort Change job due to. . . .

1

-

I I P-ACT 1 I 1

-

Symptom indices summary S-DIS: based only on “distal” region I 1

2 1 1 1

I I S-ANY: based on “all” regions 1 1 1 1

I 1 1

S-PRO: based on “proximal” region Ever I 2 2 year S-SPC: based on CTS-specific questions I 2 year 1 2 year 1 2 year I

-

Recurrent proximal symptoms Recurrent proximal (sum of “yes”) Recurrent burning, tingling, or pain Pain awakening from sleep Difficulty with knob, lock Positive Phalen test

*Composite indices are calculated as the sum of points for indicated questions. P-ILL, personal illnesses; P-ACT, personal activities; CTS, carpal tunnel syndrome.

checker = 5 ; “75er” or apprentice checker = 4;clerk or helper = 3 ; other The weighted exposure months were then accumulated for each subject.

=

1).

RESULTS

Table IV summarizes the distributions for each of the composite indices of personal factors, exposures, and symptoms. The data distributions are consistent with a priori expectations, suggesting validity. For example, average checking hours over the past 2 weeks (E-CHR) of 37 hours are consistent with informal discussions with workers. The distributions of the symptom outcome variables are skewed to the right, indicating that symptoms are clustered in a small number of individuals. The same is

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TABLE IV. Summary of Variables Employed in Study of Supermarket Workers* Symbol Personal factors P-ILL

P-ACT

Meaning Personal illness (based on diseases, pregnancies, UE surgery, UE casts, rheumatoid arthritis, fracture) Personal activities (based on hobbies, previous jobs)

Mean

S.D. Skewness S.R. Median

0.363

0.55

1.15

5.21

0.00

5.05

6.77

1.64

7.46

2.15

2.69 30.1 27.6

-0.53 0.04 1.99

-2.41 0.19 9.06

5.00 40.0 9.9

2.39 3.36 2.29 1.12

1.35 1.80 1.24 1.62

6.13 8.17 5.64 7.38

1.00 1.00 0.00 0.00

Exposure factors E-JOB Job title: clerk = 31 (25%), checker = 56 (45%), other = 37 (30%) E-WHR Work hours on interview day 4.55 E-CHR 36.86 Checking hours in past 2 weeks E-RYR 22.15 Weighted work risk years (weights: checker = 5 , 75er = 4, clerk = 3, other = 1) Symptom factors S-DIS Symptoms-distal (lower arm, hand) 1.87 Symptoms-any S-ANY 2.60 S-PRO Symptoms-proximal (upper arm) 1.76 s-SPC Symptoms-CTS-specific 0.72 (hand burn, pain at night, weakness)

*Variables used to aggregate data are shown. Positive skewness indicated tail to right; SR is the ratio of skewness to standard error; UE, upper extremity; CTS, carpal tunnel syndrome.

true of the personal illness (P-ILL) index and the CTS-specific symptom (S-SPC) index. Table V provides illustrative data about responses to several questions. The results of categorical analyses of relationships between outcomes and potential risk factors are shown in Tables VI and VII. Only analyses for the relationship of a score in the upper quartile of outcome vs. possible risk factors are shown; similar results were obtained using the outcome data based on the median. Personal activities were statistically significantly related to all four of the outcome variables. A history of personal illnesses considered to be associated with CTS was related to the presence of any symptoms (S-ANY) and distal arm symptoms (S-DIS), but not to the CTSspecific symptom index (S-SPC). Among the exposure variables, the variable representing cumulative exposure, E-RYR, was most related to the outcomes. It was significantly related to CTSspecific symptoms (S-SPC), upper (proximal) arm symptoms (S-PRO), and all symptoms (S-ANY); it was related to lower (distal) arm symptoms (S-DIS) to a borderline significant degree. Hours of checking work of the preceding 2 weeks (E-CHR) was significantly related to S-DIS and S-PRO; it was loosely related to the CTS-specific symptom index. Notably, job title per se was not related to any of the outcome measures, and hours worked on the day of the interview (E-WHR) was only related to S-DIS (p = 0.049). Logistic regression analyses, shown in Table VIII, allowed simultaneous adjustment of the relationship between exposure and outcome variables for the effects of potential confounders (personal factors, age, sex). Values in Table VIII are shown

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TABLE V. Symptom Frequencies (Examples) in Study of Supermarket Workers*

Burning Pain Weakness Tingling Proximal Key in lock Knob turning Tool dropping Total

Checkers

Clerks

0 12 4 9

0 9 5 4

18 8 10

9 7

13 32

Other

Total

3

3 29 16 23

8

7 10

41

7 6

14 7 5 7

55

37

124

22 22 26

Recall period 2 year 2 year 2 year 2 year Ever Ever Ever Ever

Site” H-W-F H-W-F H-W-F H-W-F A-E-U-S-N H-F H-F H

*Frequency of positive responses to specific symptoms (yesho questions) for several sample sites are shown. “H, hand; W, wrist; F. fingers; A, arm; U , upper arm; N , neck; E, elbow; S, shoulder.

for those factors whose coefficients in the regression equations suggested significant relationships with outcomes. Table VIII shows the coefficients and the risk associated with the factor, calculated as the exponential (exp) of the coefficient. In addition, the 95% confidence intervals for these exp (coefficients) are shown. Personal factors were related to the outcomes. For example, an individual whose P-ILL score is 2 standard deviations (s.d.) above average has a 2.5 fold increased risk of being in the upper quartile of total (S-ANY) symptoms. Being 2 s.d. above mean in P-ACT implies a 3.1 fold increased risk of CTS-specific symptoms. Job title itself was inversely related to several adverse outcomes (S-DIS, S-PRO). In Table VIII, Job Title is shown by two design variables: “Other” has “0” for both, clerks have one for the first, and checkers have one for the second. Thus, since coefficients are negative, the job title itself (for checkers and clerks) does not imply higher risk. This suggests that workers who checked were not simply reporting more symptoms, because they had learned the purpose of our study. Women are more likely than men to be in the upper quartile of all symptoms (S-ANY) and lower arm/wrist/hand symptoms (S-DIS). In addition, they are at increased risk of having more than median upper arm symptom scores (S-PRO). Age was related only to likelihood of being in the upper quartile of S-ANY. Hours worked on the day of the interview was not associated with any of the adverse outcomes. This also lends support to the validity of the questionnaire data, which rely on recall of symptoms for longer time periods. Hours of checking work in the preceding 2 weeks (E-CHR) was associated with increased risk of being in the upper quartile of three symptom groups: all symptoms (S-ANY), distal arm symptoms (S-DIS), and proximal symptoms (S-PRO). The integrated weighted exposure index (E-RYR) was related to all symptoms (S-ANY) and proximal/upper arm (S-PRO) symptom indices. Among checkers, work factors-both recent and cumulative-affected symptoms. For example, predicted risk of being in the upper quartile of symptoms for proximal symptoms (S-PRO) is strongly affected: a checker with 16 hours of checking over the past 2 weeks and 3.4 weighted risk years (corresponding to < 1 year) has a predicted risk of 0.03, while it is 0.52 for 64 hours of checking per 2 weeks and 76

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Harber et al.

TABLE VI. Relationship of Outcomes to Personal Risk Factors in Study of Supermarket Workers* Personal factors outcome

P-ILL

S-ANY-Q 0 I S-DIS-Q 0 I S-PRO-Q 0 1

P-ACT

n

1.5

88 36

63 20

25 12

88 36

61 22

98 26 76 48

P

2.1

P

0 4

0.004'

51

37 25

0.006'

II

27 10

0 4

0.006'

49 13

39 23

0.048b

66 17

30 7

2 2

0.343

54 8

44 18

0.027'

51 32

24 13

I

0.298

47 15

29 33

0.001'

3

s-SPC 0 1

*See footnotes to Table VII for explanation. Q refers to upper quartile (also for Tables VII, VIII). ap < 0.10. bp < 0.05. 'p < 0.01.

TABLE VII. Relationship of Outcomes to Work Risk Factors in Study of Supermarket Workers* Work factors outcome

E-JOB

E-CHR

E-RYR

n

1

2

3

p

I0

p

15.7

p

88 36

23 14

25 6

40 16

33 8

55 28

0.101

58 13

30 23

0.002'

0.25

88 36

24 13

23 8

41 15

0.618 0.62

34 7

54 29

0.039'

55 16

33 20

0.065'

98 26

27 10

28 3

43 13

0.18

37 4

61 22

0.031'

66 5

32 21

0.OOO'

76 48

20 17

19 12

37 19

0.51

30 11

46 37

0.056a

51 20

25 28

0.005'

S-ANY-Q 0

I S-DIS-Q 0 1

S-PRO-Q 0 I s-SPC 0

I

*Results of contingency table (Chi square) analyses between risk factor indices and symptom outcome indices are shown. Calculation of indices is shown in Table 111. The indices' definitions are also in Table Ill. ap < 0.10. 'p < 0.05. cp < 0.01.

weighted risk years (equivalent to 15 years of work as a checker). For lower arm symptoms (S-DIS), the estimated probability of being in the upper quartile symptomatically is 0.05 for a male with 80 hours, and 0.45 for a female with 80 hours checking12 weeks.

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TABLE VIII. Logistic Regression Results in Studv of Suwrmarket Workers* P-ILL S-ANY-Q Coeff. exp(coeff) CL(upper) CL(lower) S-DIS-Q Coeff. exp(coeff) CL(uppe0 CL(lower) S-PRO-Q Coeff. exp(coeff) CUupper) CL(lower) s-SPC Coeff. exp(coeff) CUupper) CL(lower)

P-ACT

0.859b 2.360 5.001 I . 1 14

E-CHR

E-RYR

E-SEX

0.015' 1.016 1.03I 1.001

0.083" 1.087 1.153 1.025

TTL-1

TTL-2

0.049"

Constant -3.37

1.050 1.097 I .005

0.027' 1.028 1.046 1.009 0.029' 1.030 1.053 1.007

E-AGE

0.928b 2.529 6.333 1.010 0.030" 1.031 1.051 1.012

-0.700 -1.740 0.496 0.175 1.549 0.638 0.159 0.048

-1.57

- 1.730

-2.18

0. I78 0.902 0.035

-1.950 0.142 0.590 0.034

-0.89

*Logistic regression results are shown for the symptom outcome indices, defined in Table 111. The Table shows the results of regression of odds of having symptom index in the upper quartile on the predictor indices. Regression coefficients are shown only for those variables which entered the forward stepwise regression. Coeff, regression coefficient; CL, 95% confidence limit for the coefficient. p values for the coefficients are denoted by: ap < 0.01; 'p < 0.05; 'p < 0.10. Constant, constant from regression model. TTL- 1 and -2, job title variables: checkers are coded as 0, I for TTL- I , TTL-2, respectively; clerks as 1,O; others as 0,O.

Viewed in toto, the results show that there are relationships between many types of symptoms of the upper extremity and both personal and occupational factors. The relationships were not due only to confounding by age or sex. DISCUSSION

Upper extremity problems are common in many occupations [Punnet et al., 1985; Silverstein et al., 1986, 1987; Ayoub, 1990; Birbeck et al., 1975; Armstrong et al., 1979; Bleeker, 1986, 1987; Cannon et al., 1981; Rodgers, 19871. Much of the work in many of these occupations is quite stereotyped, reflecting repetitious performance of the same motion. Checkstand operations, however, are much more difficult to characterize since a wide variety of objects are manipulated. The potential of checking work for producing CTS and other upper extremity cumulative trauma disorders (UECTD) has been recognized by many supermarket workers as well as investigators. In several of these studies [Barnhart and Rosenstock, 1987; Margolis and Kraus, 19871, questionnaires were completed by mail or data were derived from anecdotal clinic records. Evaluations of the physical characteristics of checkstands have previously suggested the potential for problems [Wallersteiner, 1981; Wilson

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and Grey, 19841. The current study provides supplementary information, since it employed an extensive interviewer-administered questionnaire and since recruitment was facilitated by a joint union-management endorsement and full cooperation. In addition, interviewing was performed at the worksite, thus facilitating participation of subjects. The study demonstrated that supermarket employees report a variety of symptoms related to the upper extremity. The problems are quite varied in nature, and involve both the proximal upper extremity (upper aspects of the arm and shoulders) as well as the wrist and hands. The symptoms may be due to several different clinical problems. For example, CTS may produce pain in the wrist and hand; formal diagnosis of this problem generally requires nerve conduction testing, but symptoms may be strongly suggestive. A small group of workers reported symptoms which are commonly associated with CTS (e.g., burning pain, pain at night). However, these represent only a small proportion of the symptoms reported. Other problems such as tenosynovitis of the hand and wrist tendons, bursitis at the shoulder, and other nonspecific illnesses might also be present [Travers, 19881. The informal survey of Ayoub [ 19901 showed that shoulder and neck complaints were much more common than hand and wrist symptoms. This is consistent with this current study. While symptoms alone cannot lead to specific medical diagnoses, they can provide a measure of the overall health and functional impact. The questionnaire is useful for epidemiologic purposes in estimating the impact of exposure on symptoms; it may also be useful as a screening tool to select individuals for more in-depth medical evaluation later [Elsey and Wagner, 19871. This study demonstrated that there is a clear relationship between work as a supermarket checker and the presence of upper extremity symptoms. Symptoms involved both the proximal and distal portions of the upper extremities. Both relatively short-term measures of exposure (e.g., hours checking during the past 2 weeks) as well as long-term exposure measures (cumulative weighted months as checker) were related to the presence of symptoms. These relationships were consistently seen in multiple analyses. The analyses of the relationship between exposure variables and outcomes were performed with and without age adjustment, and they showed consistent results. Analysis with age adjustment was performed to assure that any apparent relationship between cumulative exposure and adverse outcome was not simply due to age alone, since age confounds years of exposure (older workers have had more opportunity to accumulate years of exposure). Conversely, analysis without age adjustment was performed to assure that overadjustment by collinear variables did not occur. Thus, while age was itself related to several variables, this did not, in itself, account for the full relationship. Since both recent work factors (e.g., hours checked in the preceding 2 weeks) as well as long-term exposure factors (e.g., cumulative checker months) were related to adverse outcomes, the symptoms are unlikely simply to represent short-term, fully reversible effects, nor are they likely simply to reflect reporting of length of recent work. Furthermore, the presence of symptoms in this report is unlikely just to represent nonspecific dissatisfaction with working conditions since there is a clear relationship to exposure factors. Randomly reported symptoms would be very unlikely to show such a relationship. Furthermore, although workers were aware that this was a

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study with an a priori suspicion that checking work was particularly associated with symptoms, job title itself was not an associated factor. This study supports the cumulative effect of repetitive mechanical stress to the upper extremities. CTS and similar disorders requiring intensive therapy do not develop suddenly, but rather are a consequence of accumulated effects. Hence, cumulative stress related symptoms must be considered seriously. The symptoms themselves are important. Such discomfort is likely to affect both the individual worker and the employer. Many of the symptoms described may continue after completion of work and therefore affect personal activities. They may directly affect productivity; in a labor intensive operation, any decrease in throughput is quickly reflected in significantly increased overall costs. Furthermore, intangible effects to the employer may be interference with good customer relations. The checkout operation is generally the major human contact between customers and store personnel. The statistical methods utilized in this analysis reflect the complexity of investigations of chronic musculoskeletal disorders with incompletely disabling effects. Particularly in epidemiologic (rather than clinical) studies, lack of a clear, unique outcome measure generally mandates utilizing multiple questions. Use of a brief outcome questionnaire can create serious concern about the specificity and value of the outcome measures. In this study, we employed an a priori combining scheme. Even with detailed clinical examinations, there is often considerable disagreement among occupational medicine specialists and orthopedists concerning specificity of diagnosis. Furthermore, many clinical findings in the musculoskeletal system are subject to considerable interobserver variability. What are the implications for prevention? First, this study, in conjuction with others, strongly suggests that there is indeed potential for cumulative trauma disorders to develop in supermarket checkers. Second, the wide variety of symptoms noted suggests that attention should not focus on a single disorder such as CTS, but rather that the entire spectrum of upper extremity disorders requires attention. By clearly stating to workers and investigators that the problem is multifaceted, prevention should be facilitated. It will be accomplished by improving the quality of research and encouraging workers to report symptoms rather than fearing that they necessarily have a serious illness (e.g., CTS) which might preclude their continued work. Third, the questionnaire utilized in this study was able to show a continuum of symptoms. Further development of such a questionnaire may provide a useful screening tool which may be utilized to select those workers who require more specific, detailed medical attention or whose work stations require modification. Fourth, an effective questionnaire may be useful in surveillance of worker populations to select those worksites which require careful ergonomic assessment and intervention to decrease symptom prevalence (and presumably risk of disabling disorders). This study does not permit separation of the effects of supermarket checking from use of laser scanners since, in this population, use has been highly correlated. The scanners were introduced into this chain at about the same time in all stores, and therefore length of work is very highly collinear with length of scanner use. In summary, this study showed that even with statistical adjustment of the relationship between exposure and symptoms for confounding by age, personal illnesses, and previous jobs, there is a clear relationship of both short-term and long-term exposure measures with the presence of symptoms of UECTD. Personal factors as well as occupational factors are important in affecting upper extremity symptoms.

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ACKNOWLEDGMENTS

The authors thank Katherine Howard and Robert Appleby for data collection assistance; Andrea Zinder and the officers of United Food and Commercial Workers, Local 770; and Bonnie Schumaker and Harley Delano of ABC Supermarkets for their cooperation. The authors also thank Ana Osorio, M . D . , for her advice, and Nancy Marshello and Katty Kim for preparing the manuscript. Supported by grant AR 36834 from the National Institutes of Health. REFERENCES Armstrong TJ, Chaffin DB (1979):Carpal tunnel syndrome and selected personal attributes. J Occup Med 21 :481-486. Ayoub MA (1990): Ergonomic deficiencies: 1. Pain at work. J Occup Med 3252-57. Barnhart S, Rosenstock L (1987): Carpal tunnel syndrome in grocery checkers. A cluster of a work related illness. West J Med 147:37-40. Birbeck M, Beer T (1975): Occupation in relation to the carpal tunnel syndrome. Rheum Rehab 14: 2 18-22 1. Bleecker M (1986): The carpal tunnel syndrome. Semin Occup Med 1:131-139. Bleecker M (1987): Medical surveillance for carpal tunnel syndrome in workers. J Surg 12A:845-848. Cannon L, Bernacki E, Walter S (1981): Personal and occupational factors associated with carpal tunnel syndrome. J Occup Med 23:255-258. Dixon WJ (1983): “BMDP Statistical Software.” Berkeley: University of California Press. Elsey D, Wagner S (1987): Proposed screening tool for the detection of cumulative trauma disorder of the upper extremity. Am J Hand Surg 12:931-935. Engelman L (1988):PLR. Stepwise logistic regression. In Dixon WJ (ed): “BMDP Statistical Software.” Vol. 2. Berkeley: University of California Press, pp 1013-1024. Margolis W, Kraus JF (1987): The prevalence of carpal tunnel syndrome symptoms in female supermarket checkers. J Occup Med 29:953-956. Punnett L,Robins JM, Wegman DH, Keyserling WM (1985): Soft tissue disorders in the upper limbs of female garment workers. Scand J Work Environ Health 11:417-425. Rodgers S (1987): Afterword. Semin Occup Med 2:79-81. Ryan GA ( 1989): The prevalence of musculoskeletal symptoms in supermarket workers. Ergonomics 32~359-371. Silverstein BA, Fine LJ, Armstrong TJ (1986): Carpal tunnel syndrome: Causes and preventive strategy. Semin Occup Med 1:213-219. Silverstein BA, Fine LJ, Armstrong TJ (1987): Occupational factors and carpal tunnel syndrome. Am J Ind Med 1 I :343-358. Travers P (1988): Soft tissue disorders of the upper extremities. Occup Med 3:271-283. Wallersteiner U (1981): Occupational health disorders of cashier operators in supermarkets. Proc of the Human Factors Assoc of Canada, Toronto. Wilson JR, Grey SM (1984): Reach requirements and job attitudes at laser-scanner checkout systems. Ergonomics 27: 1247-1266.