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Journal of Gerontology: BIOLOGICAL SCIENCES Copyright 1998 by The Gerontological Society of America 1998. Vol. 53A, No. 5, B362-B368 Comparison of Cross-Sectional and Longitudinal Designs in the Study of Aging of Upper Extremity Performance 12 12 12 1 Johanne Desrosiers, Rejean Hebert, Gina Bravo, and Annie Rochette Downloaded from https://academic.oup.com/biomedgerontology/article/53A/5/B362/588231 by guest on 19 August 2022 'Centre de Recherche en G6rontologie et Geriatrie, Sherbrooke Geriatric University Institute, Sherbrooke, Qu6bec, Canada. Taculte" de Me*decine, University de Sherbrooke, Sherbrooke, Quebec, Canada. The purpose of the study was to compare two research designs, namely the cross-sectional design and the longitudi- nal design, in the context of upper extremity performance and age-related changes. Upper extremity performance of 360 randomly recruited, healthy, community-dwelling elderly persons was evaluated with reliable and valid sensori- motor tests. Three years later, survivors (n = 264) were reevaluated with the same tests. In many tests, cross-sec- tional and longitudinal designs were comparable for estimating the changes in upper extremity performance with age. However, in some tests, the decline with age using a cross-sectional design was underestimated. The upper extremity performance decline observed with the longitudinal design was larger than the decline predicted with the cross-sectional design. The withdrawal and survivor biases related to the longitudinal design and the cohort bias associated with the cross-sectional design may, in part, explain these results. N the study of age-related changes, two major research used by clinicians to compare the performance of their I designs may be used: the cross-sectional design and the patients to that of a normal population. These data are longitudinal design. Both designs have particular advan- important in gerontology because it is important to differ- tages and disadvantages. Even though the cross-sectional entiate between the difficulties attributable to normal aging design is less expensive and frequently used in the devel- and those attributable to pathologic aging. opment of normative data, this design may have an impor- The objective of the present study was to compare cross- tant limitation in the study of aging. This limitation is the sectional and longitudinal designs in the context of upper cohort bias in that people born at the beginning of the cen- extremity performance changes with age. The method- tury have not experienced the same events nor under the ologic relevance of the study is based on the appropriate- same conditions as younger people, which may influence ness of the cross-sectional design for studying age-related their performance. changes. The clinical relevance of the study is based on the In addition to being longer and more expensive, the durability of the normative data developed with a cross- study of aging with a longitudinal design presents other sectional design. If the performance decline predicted by possible biases related to withdrawal (refusals) and to sur- the cross-sectional design is equivalent to the decline ob- vival (deaths or ineligibility factors). The bias associated served with the longitudinal design, normative data may be with withdrawal was studied by Hubert et al. (1) with 500 applied to successive cohorts. If not, they should be regu- subjects aged 75 years and older, followed on a 3-year larly revised. period. Men had more tendency to drop out, but no health- related variables were associated with withdrawal from the METHODS study. Mihelic and Crimmins (2) found that withdrawal (nonresponse) was associated, among other variables, with Subjects age (older people), living situation (alone), and functional During 1992-1993, a random sample of 360 subjects (179 impairments (more), but not with gender. The survival bias women and 181 men), aged 60 and older (mean, 73.9; SD, was more serious because people who died during a study 8.0), and living at home was drawn from the electoral list of were those whose health was more affected (3-5). the city of Sherbrooke, Quebec, Canada. The purpose of this Upper extremity performance is an important prerequi- cross-sectional study was to develop reference values for site to functional independence in older people (6-9). With many upper sensorimotor parameters (10). The eligibility the aging of the population, more and more people may criteria were lucidity (clinical judgment), independence in have a decline in upper extremity performance secondary activities of daily living (eating, washing, dressing, groom- to age-related sensorimotor deficits. Therefore, sensorimo- ing, and toiletting), and absence of upper extremity impair- tor parameters related to good upper extremity perfor- ments (neurologic or orthopedic). The participation rate in mance, such as gross and fine dexterity, motor coordina- this study was 78% and statistical analyses revealed no dif- tion, global performance, grip strength and sensibilities, are ference between those who refused to participate and those often measured in clinical settings to monitor their evolu- who accepted in terms of age, gender, height, weight, domi- tion. Reference values or normative data are frequently nance, self-perceived health, and current activity level (11). B362 COMPARISON OF CROSS-SECTIONAL AND LONGITUDINAL DESIGNS B363 Three years later (1995-1996), the same subjects were Statistical Analyses recontacted to replicate the study. The same eligibility crite- To simplify the results presentation, the terms time 1 and ria were applied and subjects who no longer satisfied these time 2 will be used respectively for the first evaluation in criteria were excluded. As in the cross-sectional study, peo- 1992-1993 and the second in 1995-1996. t test and chi- ple who refused to participate, although eligible, were square analyses were used to compare, at time 1, personal asked to reply to a short telephone questionnaire in order to characteristics and upper extremity performance of subjects estimate the refusal bias. who did not participate in the second measurement with those who participated in both measurements. The same sta- Procedure tistical tests were used to verify if those who refused to par- The same evaluation procedure was followed for the two ticipate were comparable in personal characteristics, at time Downloaded from https://academic.oup.com/biomedgerontology/article/53A/5/B362/588231 by guest on 19 August 2022 measurement periods. To avoid an information bias in the 2, to those who agreed. Paired t tests were used to verify if second measurement, data from the first assessment were the changes between time 1 and time 2 were significant. not available to the examiner. For both measurements, each The main analysis of this study focused on comparing subject was evaluated once at the Upper Limb Function upper extremity changes predicted with the cross-sectional Measurement Laboratory at the Centre de Recherche en design (predicted difference: PREDDIF) to changes ob- Ge'rontologie et G6riatrie or at their home under the same served by the longitudinal design (observed difference: conditions, but not by the same examiner who took the first OBSDIF). The observed difference is defined by the ob- measurement. The duration of each measurement varied served score at time 1 minus the observed score at time 2. between VA and 2 hours, depending on the subject, includ- The predicted difference is calculated by subtracting the ing a rest. This study was submitted to and accepted by the predicted score at time 2 from the score at time 1. The pre- Research Ethics Committee of the Sherbrooke Geriatric dicted score at time 2 was estimated using simple linear University Institute. regression analyses developed with time 1 data (cross-sec- Anthropometric data were first collected, followed by a tional design), where age was the independent variable and structured interview in order to quantify personal characteris- the upper extremity test score was the dependent variable. tics potentially related to upper extremity performance: age, In some tests, a high score indicates a low performance living situation (living alone, living with somebody else, liv- whereas in others, the scoring system is reversed. Conse- ing in a senior's residence), self-perceived health status, and quently, in order to facilitate the data interpretation, the pre- activity level. Regarding self-perceived health status, the dicted and observed differences were standardized so that subject was asked: "Compared to other people your age, how positive numbers represent a decline. would you describe your present health? Excellent, good, For each upper extremity test, a t score was attributed to fair, or poor." Activity level was evaluated using questions each subject. These t scores were defined by regarding the frequency of physical activities. Based on this (OBSDIF-PREDDIF) information, the evaluator estimated the level of activity on a global scale: very active, active, slightly active, or sedentary. Subsequently, upper extremity tests were administered. where Spred is the standard deviation of the predicted score model. A t test was then used to check if, on average, these Measurement Instruments t scores were null. If the longitudinal and cross-sectional Many tests were chosen in order to reflect upper extrem- designs described the aging effect in the same way, then the ity function. These tests are all reliable and valid. Gross observed difference from the longitudinal design and the manual dexterity was measured with the Box and Block predicted difference from the cross-sectional design should Test (12-14) whereas fine manual dexterity was measured be equivalent. In order to confirm the null hypothesis that with the Purdue Pegboard (15-17). Global upper extremity no difference was observed between the observed upper performance was estimated with the TEMPA (Test Evaluant extremity performance decline (longitudinal design) and la performance des Membres superieurs des Personnes the predicted decline (cross-sectional design), the differ- Ag6es) (18-20). ences should be near 0. To take into account the high num- Upper extremity motor coordination was estimated with ber of statistical analyses done, the level of p < .01 was the Finger-Nose Test (21-23). Grip strength was measured retained. with two apparatuses: the Jamar dynamometer (11,24) and the Martin vigorimeter (25,26). The Jamar dynamometer RESULTS was set at the second position and the large bulb of the Of the original 360 subjects in the cross-sectional study, Martin vigorimeter was selected for all subjects. 264 (128 women and 136 men) with a mean age of 75.0 Tactile recognition was estimated with the Pick-Up Test (SD = 7.4) participated in the second measurement. There- (27), modified by Dellon (28,29). Static and moving two- fore, 96 subjects were not reevaluated: 26 had died, 15 point discriminations were measured on the palmar face of were not located, 29 refused, and 26 were no longer eligible the distal phalanx of the index and little finger of both because of the development of impairment. hands, using the Mackinnon-Dellon disk-criminator (30). When characteristics at time 1 of the 96 drop-out subjects Touch/pressure thresholds (31) were estimated at the distal were compared to those who participated, drop-outs were phalanx of the index of the dominant hand using the older (p < .001), had a lower body mass index (p = .006), per- Semmes-Weinstein monofilaments (32). Finally, the same ceived themselves in poorer health (p = .001), were less filaments were used for the tactile localization test (33). active (p = .001), and were more likely to live in a senior's B364 DESROSIERS ETAL. residence (p = .04). From the phone questionnaire at time 2, Table 1 presents the results related to the objective of the the subjects who refused to participate in the second mea- study. For each test, when significant differences were found surement (n = 29) were older (p = .01), perceived themselves between the upper extremity performance of the women and in poorer health (p < .01), and were less active {p < .001) than the men, the results are presented by gender. If not, they those who participated. In addition, the subjects who partici- were combined. The first two columns of the table report pated in both measurements showed, at time 1, significantly upper extremity scores obtained at the time 1 measurement higher performance on all upper extremity tests (p < .01) than (1992-1993) and at the time 2 measurement (1995-1996). those who participated in only one measurement, with the The third column shows the result of the difference between exception of the tactile localization of the left index (p = . 14). the two measurements (time 1 minus time 2), which corre- Downloaded from https://academic.oup.com/biomedgerontology/article/53A/5/B362/588231 by guest on 19 August 2022 Table 1. Comparison of the Observed and Predicted Differences OBSDIF T PREDDIF OBSDIF - 1 2 1 PRFnniF n 92-93 (T ) 95-96 (T ) (T score Predicted (T' score r 1 2 2 2 p>rd Score T Score T T score) score T pred. score) S value Box and Block Test (No. of blocks) Men and women Right hand 68.9 (8.3)* 59.6 (7.6)* 9.3 (6.8)* 66.2 (4.7)* 2.7 (7.3)* 0.85 (0.9)* <.001 Left hand 68.2 (8.7) 59.2 (7.5) 9.0 (6.5) 65.6 (4.8) 2.6 (7.6) 0.80 (0.9) <.001 Purdue Pegboard (No. of pins) Women Right hand 13.3(1.8) 12.4 (2.3) 0.9(1.9) 12.7(1.1) 0.5(1.5) 0.24(1.2) .03 Left hand 12.5(1.9) 11.7(2.3) 0.9(1.6) 12.0(1.2) 0.6(1.6) 0.18(1.0) .05 Both hands 10.1 (1.9) 9.3(1.9) 0.8(1.5) 9.6(1.1) 0.5(1.6) 0.17(0.9) .04 Total 35.9 (5.0) 33.2 (6.0) 2.6 (3.6) 34.3 (3.4) 1.6(3.9) 0.24(1.0) .01 Assembly 27.5 (6.3) 25.5 (6.5) 2.0 (5.0) 25.5 (3.5) 2.0 (5.5) -0.007 (0.9) .93 Men Right hand 11.8(1.9) 10.8(2.1) 0.9(1.7) 11.1(1.1) 0.7(1.8) 0.16(1.0) .07 Left hand 11.5(2.0) 10.5 (2.2) 1.0(1.7) 10.8(1.3) 0.7(1.7) 0.17(1.1) .08 Both hands 9.0(1.9) 8.2 (2.0) 0.8(1.4) 8.4(1.1) 0.7(1.7) 0.11 (1.1) .27 Total 32.3 (5.3) 29.5 (5.7) 2.8(3.1) 30.3 (3.5) 2.0 (4.5) 0.17(1.1) .07 Assembly 24.4 (6.0) 22.0 (6.0) 2.3 (4.0) 22.2 (3.8) 2.1(5.1) 0.03 (0.9) .73 TEMPA (log. sec.) Pick up and move ajar Women Right hand 0.5 (0.2) 0.5 (0.2) 0.03 (0.2) 0.5(0.1) 0.03 (0.2) 0.03 (0.9) .75 Left hand 0.5 (0.2) 0.5 (0.2) 0.02 (0.2) 0.5(0.1) 0.03 (0.2) -0.02 (0.9) .79 Men Right hand 0.4 (0.2) 0.4 (0.2) 0.05 (0.3) 0.4(0.1) 0.04 (0.2) 0.05 (0.8) .49 Left hand 0.4 (0.2) 0.4 (0.2) 0.04 (0.3) 0.4 (0.4) 0.03 (0.2) 0.06 (0.8) .38 Open ajar and take a spoonful of coffee Women and men 2.2 (0.2) 2.3 (0.2) 0.11(0.2) 2.2(0.1) 0.06 (0.2) 0.20(1.1) .004 Pick up a pitcher and pour water into a glass Women and men Right hand 2.1 (0.2) 2.1 (0.2) 0.04 (0.2) 2.1 (0.1) 0.05 (0.2) -0.008(1.0) .89 Left hand 2.1 (0.2) 2.1 (0.2) 0.03 (0.2) 2.1 (0.1) 0.05 (0.2) -0.13(0.9) .02 Unlock a lock and open a pill container Women and men 2.4 (0.2) 2.6 (0.2) 0.17(0.2) 2.4 (0.2) 0.05 (0.2) 0.56 (0.9) <.001 Tie a scarf around one's neck Women and men 2.1 (0.3) 2.3 (0.3) 0.13(0.3) 2.2 (0.2) 0.11(0.2) 0.09(1.1) .34 Handle coins Women Right hand 2.0 (0.2) 2.2 (0.2) 0.15(0.2) 2.1 (0.1) 0.04 (0.2) 0.60(1.0) <.01 Left hand 2.1(0.2) 2.2 (0.2) 0.09 (0.2) 2.2(0.1) 0.04 (0.2) 0.30(1.1) .002 Men Right hand 2.1 (0.2) 2.3 (0.2) 0.14(0.2) 2.1 (0.1) 0.05 (0.2) 0.50(1.3) <.001 Left hand 2.2 (0.2) 2.3 (0.2) 0.11(0.2) 2.2(0.1) 0.04 (0.2) 0.37(1.3) <.001 Pick up and move small objects Men Right hand 2.1(0.2) 2.2 (0.2) 0.06 (0.2) 2.1 (0.1) 0.05 (0.2) 0.04 (0.9) .60 Left hand 2.1(0.2) 2.2 (0.2) 0.05 (0.2) 2.1 (0.1) 0.05 (0.2) 0.01 (0.9) .89 Continued on next page COMPARISON OF CROSS-SECTIONAL AND LONGITUDINAL DESIGNS B365 Table 1. Comparison of the Observed and Predicted Differences (Continued) OBSDIF T2 PREDDIF OBSDIF - 2 1 PREDDIF 92-93 (T) 95-96 (T ) (T score - Predicted (T score - P 1 2 2 2 gpncd Score T Score T T score) score T pred. score) value Finger-Nose Test (No. of movements) Women Right upper limb 22.3(4.1) 20.2 (3.8) 2.0(4.1) 21.2(2.1) 1.0(3.5) 0.27(1.1) .004 Left upper limb 21.6(4.1) 19.4(3.7) 2.2 (3.6) 20.6(2.1) 1.0(3.6) 0.33(1.0) <.001 Men Downloaded from https://academic.oup.com/biomedgerontology/article/53A/5/B362/588231 by guest on 19 August 2022 Right upper limb 23.0 (3.9) 22.5 (4.0) 0.5 (3.6) 21.8(2.0) 1.2(3.5) -0.18(1.0) .03 Left upper limb 22.9 (4.2) 21.6(3.8) 1.3(3.3) 21.5(2.2) 1.3(3.7) -0.01 (0.9) .88 Jamar dynamometer (kg) Women Right hand 24.2 (4.9) 23.2 (4.9) 1.0(2.8) 22.8 (2.3) 1.4(4.6) -0.08(1.0) .35 Left hand 22.5 (4.7) 22.1 (5.0) 0.4 (2.8) 21.2(2.3) 1.4(4.4) -0.21 (1.0) .02 Men Right hand 41.9(9.3) 38.9 (9.8) 3.0(4.1) 39.8 (4.9) 2.0 (8.2) 0.12(1.0) .17 Left hand 40.2 (9.4) 38.1 (9.3) 2.1 (4.0) 37.7(5.1) 2.5(8.1) -0.05(1.0) .60 Martin vigorimeter (Kpa) Women Right hand 52.2(11.2) 51.0(11.9) 1.2(7.1) 49.7 (4.2) 2.5(10.8) -0.12(1.1) .18 Left hand 50.4(10.9) 48.3(11.3) 2.0 (7.7) 48.1 (4.1) 2.3(10.6) -0.02(1.0) .80 Men Right hand 81.2(18.1) 75.5(17.6) 5.7 (9.7) 76.9(11.0) 4.4(15.7) 0.09 (0.9) .24 Left hand 80.0(17.9) 74.0(17.7) 6.2(10.8) 75.3(10.3) 4.7(15.5) 0.09 (0.9) .24 Pick-Up Test (log. sec.) Eyes close-eyes open Women Right hand 2.6 (0.5) 2.7 (0.5) 0.13(0.6) 2.7(0.1) 0.06 (0.5) 0.13(0.9) Left hand 2.6 (0.4) 2.6 (0.5) 0.03 (0.6) 2.6(0.1) 0.06 (0.4) -0.07(1.0) .42 Men Right hand 2.8 (0.5) 3.1 (0.5) 0.20 (0.5) 3.0 (0.2) 0.11 (0.4) 0.21 (1.0) .02 Left hand 2.8 (0.5) 3.0 (0.5) 0.15(0.5) 2.9 (0.3) 0.11 (0.5) 0.10(1.0) .24 Two-point discrimination (mm) Static Women and men Right index 4.9 (0.9) 4.7 (0.9) -0.12(1.1) 5.0 (0.3) 0.18(0.9) -0.30 (0.9) <.001 Left index 4.9 (0.9) 4.8 (0.9) -0.06(1.1) 5.0 (0.2) 0.14(0.9) -0.21 (1.0) <.001 Women Right little finger 5.1(1.1) 5.9(1.1) 0.76(1.4) 5.3 (0.3) 0.14(1.0) 0.59(1.0) <.001 Left little finger 5.1 (0.8) 6.3(1.5) 1.23(1.5) 5.3 (0.3) 0.15(0.8) 1.21 (1.7) <.001 Men Right little finger 5.4(1.1) 6.1 (1.4) 0.59(1.3) 5.6 (0.3) 0.16(0.9) 0.45(1.2) <.001 Left little finger 5.5(1.0) 6.3(1.3) 0.77(1.4) 5.7 (0.2) 0.14(1.0) 0.64(1.3) <.001 Moving Women and men .02 Right index 4.4(1.0) 4.6(1.0) 0.27(1.1) 4.5 (0.2) 0.13(1.0) 0.13(0.9) Women Left index 4.1 (1.0) 4.6(1.0) 0.48(1.1) 4.3 (0.3) 0.18(0.9) 0.31 (1.0) .001 Right little finger 4.5(1.1) 5.3(1.0) 0.86(1.2) 4.6 (0.3) 0.15(1.0) 0.67(1.0) <.001 Left little finger 4.5(1.0) 5.3(1.1) 0.81(1.1) 4.6 (0.4) 0.16(0.9) 0.70(1.1) <.001 Men Left little finger 4.3(1.0) 4.5(1.1) 0.20(1.2) 4.5 (0.2) 0.19(1.0) 0.01 (1.0) .88 Right little finger 4.8(1.0) 5.4(1.2) 0.57(1.3) 5.0 (0.3) 0.19(1.0) 0.37(1.1) <.001 Left little finger 4.9(1.0) 5.3(1.3) 0.47(1.5) 5.0 (0.2) 0.12(1.0) 0.33(1.2) .002 Touch/pressure threshold (SW filaments number) Women 3.42 (0.4) 3.50 (0.3) 0.08 (0.4) 3.46(0.1) 0.04 (0.4) 0.12(0.9) .13 Men 3.56 (0.3) 3.61 (0.3) 0.05 (0.4) 3.62(0.1) 0.06 (0.3) -0.05(1.0) .58 Tactile localization (/12) Women and men 9.2 (2.5) 8.3(2.1) 0.95 (2.7) 8.8 (0.4) 0.34 (2.5) 0.22 (0.8) <.001 Note, p < .01, cross-sectional design differs significantly from the longitudinal design in estimating the age-associated decline. If the difference is posi- tive, the cross-sectional design underestimates the decline. If negative, the cross-sectional design overestimates the decline, •mean (SD).
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