Journal of Gerontology: MEDICAL SCIENCES 1996, Vol. 51A, No. 5, M215-M219 Copyright 1996 by The Geronlological Society of America Upper-Body Strength and Breast Cancer: A Comparison of the Effects of Age and Disease William A. Satariano and David R. Ragland Division of Public Health Biology and Epidemiology, School of Public Health, University of California at Berkeley. Background. In most studies of functional limitations in women with breast cancer, it is difficult to determine what difficulties are associated with breast cancer and what problems are likely to be found in women of the same age without the disease. In the present study, we report the age-specific prevalence of upper-body limitations in women with breast cancer over the course of one year, compared to that experienced by women of the same age without the disease. Methods. Interviews were conducted with women with breast cancer ages 40-84 at 3 months (n = 934) and 12 months after diagnosis (n = 843). were interviewed twice over the same period (n = 991 and 887, respectively). The main outcome was upper-body limitation, defined as the number of tasks requiring upper-body strength (0-4) reported by the respondent to be very difficult to complete or not done on doctor's orders. Results. ages,, and were approximately twice as likely as age-matched controls to report upper-body limitations, adjusting for race, education, financial status, and comorbidity. There was no case/control difference among those ages. At one year, the breast cancer patients ages and showed the greatest improvement. Conclusions. Many women who survive breast cancer report significant limitations in upper-body strength in the first few months, followed, especially among younger women, by a period of recuperation. Rehabilitation and home-care programs should be designed to meet the special and more persistent needs of older women. New strategies for assessing upper-body strength are also suggested. IN an earlier study, we reported on difficulties in physical functioning reported by middle-aged and elderly women with breast cancer, compared to women of the same ages without the disease (1). We found that limitations in upperbody strength, i.e., pushing, lifting, and reaching, were especially problematic for women with breast cancer. At 3 months after diagnosis, patients aged and reported greater difficulty than controls of the same age in completing tasks involving upper-body strength. However, cases aged were not disadvantaged in upper-body strength, when compared to controls, perhaps because of the high prevalence of concurrent health conditions among women in this age group. Most cases recuperated over the subsequent 9 months. At 12 months after diagnosis, cases aged seem to have greater functional reserves, enabling them to return to normal functioning more quickly than those aged, who seemed to have the most persistent problems. aged continued to have about the same level of difficulty as controls. The results of a more detailed investigation of age differences in upper-body limitation among breast cancer cases and controls at 3 and 12 months after diagnosis are reported in this article. To confirm our previous estimates of physical limitations among older breast cancer patients, we enrolled a new cohort of cases and controls aged to enhance sample size for this older age group. In addition, a younger group of women aged was included, so that functional status could be examined across a broader age spectrum. We also assessed the effects of recuperation more precisely by using a repeated measures analysis to examine changes in functional status between 3 and 12 months after diagnosis. Finally, we examined case/control differences more clearly by adjusting for the effects of selected covariates, including comorbidity. METHODS Information reported here is from the study, "Health and Functioning in Women with Breast Cancer" (HFW). The original HFW study, conducted between 1984 and 1985, was designed to provide a picture of the health, functional, and psychosocial status of women following the diagnosis and treatment of the disease (1). In the original study, 571 cases aged 55-84 were identified through the Metropolitan Detroit Cancer Surveillance System (MDCSS), a population-based cancer registry and participant in the National Cancer Institute's Surveillance, Epidemiology and End Results (SEER) program. Of these women, 463 (81.1%) were successfully interviewed. During the time between the first and second interviews, 14 patients died and 5 were institutionalized. Four hundred and twenty-two (95.1%) of the 444 surviving cases were reinterviewed about 9 months later. In addition, a total of 647 controls were recruited through telephone random-digit dialing (RDD). Five hundred and thirty-nine controls (83.3%) completed the initial interview. In the interim, 10 controls died and 3 were institutionalized. Nine months later, a total of 478 (90.9%) of the 526 survivors completed the second interview. The M215
M216 SATARIANO AND RAGLAND HFW protocol, described in detail in our previous report (1), was followed to enroll the new cohort of cases and controls. Interviews Case interviews. For the new cohort, 620 eligible cases, ages and, were identified over a 7- month period during 1987 and 1988. Of these women, 548 (88.4%) were interviewed 2 to 4 months after diagnosis. During the time between the first and second interviews, 532 of the 548 interviewed cases were still alive and not institutionalized. Fourteen cases died and 2 were institutionalized. A total of 512 (96.4%) of the 532 survivors were reinterviewed 8 to 10 months after the first interview. Control interviews. For the new cohort, 577 controls were identified through RDD. Of this number, 483 (83.7%) completed the first interview. Between the two interviews, 5 controls died and 6 were institutionalized. A total of 460 (97.5%) of the 472 survivors completed the second interview 8 to 10 months later. Questionnaire. The questionnaires for the first and second interviews, requiring 45 to 60 minutes to complete, included questions on functional status, demographics, social characteristics, and comorbidity. Most interviews were conducted in the subject's home; 5% were done by telephone. Upper-body limitation. The primary outcome measure was based on reports of difficulty in performing specific physical tasks described originally by Nagi (2). The tasks were (a) lifting objects heavier than 10 pounds, (b) lifting objects weighing less than 10 pounds, (c) pushing or pulling large objects, and (d) reaching or extending arms above or below shoulder level. Following the classification used by the Institute of Medicine, we defined a "functional limitation" as a "restriction or lack of ability to perform an action or activity in the manner or within the range considered normal that results from impairment" (3). A woman was considered "limited" if she reported that the task was either completed with "a lot" of difficulty or was not done on doctor's orders. In this analysis, we used a summary measure of upper-body limitation (0 versus 1 or more) (1). The following key variables were also included in the analysis: age at diagnosis (,,, years); race (self-report of ethnicity / Black, White); education (self-report of total number of years of education / 0-8, 9-11, 12, 13 or more years); and financial status (self-report of whether financial resources from all sources have been adequate to meet daily needs / adequate, not adequate). In addition, Body Mass Index (BMI) (weight in kilograms divided by height in meters squared) was calculated from reported heights and weights. For this analysis, BMI was divided into three categories (<22 kg/m 2, 22 to 27.29 kg/m 2, >27.29 kg/m 2 ). Comorbidity was defined in terms of the number of previously diagnosed conditions reported by the respondent from a list of 23 conditions. The list included high blood pressure, heart attack, other heart disease, stroke, diabetes, primary cancer (other than breast cancer), respiratory, gastrointestinal, or liver conditions, which, according to the respondent, currently cause some limitation in her regular activities. This variable was later categorized as 0, 1, 2, 3 or more comorbid conditions. Study Sample The analysis for this study was based on the complete HFW sample (the original and new cohorts). One thousand and eleven cases were interviewed 3 months after diagnosis, resulting in an overall response rate of 84.9% (1,011/1,191). Approximately 9 months later, 934 (92.4%) of the cases were reinterviewed. Of the 1,224 controls identified through RDD, 1,022 (83.5%) completed the first interview. Nine hundred and thirty-eight (91.8%) of the 1,022 controls were reinterviewed approximately 9 months later. Although the response rate for the cases was relatively high (84.9%), women with remote-stage disease were less likely to be interviewed (70.5%) than were women with local (84.3%) or regional disease (85.6%) (p <.01). In addition, women ages were more likely to be interviewed (92.7%) than were older women years, 81%; years, 80.5%; years, 80%) (p <.01). No difference was found, however, in the response rates for Black and White women (p > 0.2). With regard to controls, there was no statistically significant difference in the response rate by either race (p =. 10) or age (p > 0.2). Statistical Analysis The analysis of upper-body limitation in relation to age and time (3 and 12 months after diagnosis) was done in several steps. First, a logistic regression model was used to evaluate dichotomous upper-body limitation at 3 months after diagnosis (0 vs 1 or more upper-body task limitations). Comparisons were made for cases vs controls (case/control) within each age group (,,, ), adjusting for race, education, financial status, and comorbidity. These covariates were shown in preliminary analyses to be significantly associated with limitations in one or more upper-body tasks. Using the logistic model for each age group, the adjusted percentages of controls and cases with one or more upper-body limitations were calculated. Second, all age groups were included in the same model, and the interaction of age by case/control status was tested in relation to upper-body limitations at 3 months. This was done to determine whether the case/control difference in upper-body limitations at 3 months was greater for younger women than for older women. Third, we examined upper-body limitations at 12 months, and compared this to the results at 3 months. To accomplish this, we repeated the first and second steps for 3 months after diagnosis, and again for 12 months after diagnosis. In order that the results for 3 and for 12 months could be compared, we limited analyses in this step to only those women who participated at both 3 and 12 months. For both 3 and 12 months, comparisons were made for cases vs controls within each age group, adjusting for race, education, financial status, and comorbidity. Fourth, for a direct, within-person comparison of changes in upper-body limitation between 3 and 12 months, the data from 3 and 12 months were included in the same model. A "repeated-measures" analysis was used to exam-
UPPER-BODY STRENGTH AND BREAST CANCER M217 ine these changes, with the variable "upper-body limitations" available at both 3 and 12 months. A time (3 vs 12 months) by case/control interaction was used to evaluate change over time. Next, to test whether the change over time differed by age, we evaluated an age-by-time-by-case/ control interaction. For the first and second steps, the analysis was restricted to the 934 cases for whom complete data were available on upper-body limitation at 3 months, race, financial status, education, and comorbidity, and restriated to 991 controls for whom data were available on each variable. For the third and fourth steps, the analysis was based on 843 cases and 887 controls with complete data on these key variables plus upper-body limitation at 12 months. None of these analyses could include type of treatment and breast cancer stage as variables, since "controls," by definition, did not have a breast cancer stage, nor did they receive any treatment. We included "cohort type" (original, new) as a covariate in preliminary analyses. We found no significant interaction by cohort type and concluded that combining data from the two cohorts was appropriate. In addition, there was no significant change in the type of treatment administered to breast cancer patients between the two time periods; nor was there a change in the distribution of the severity of disease at diagnosis (as measured by breast cancer stage). RESULTS Sample Characteristics Age differences in socioeconomic and health characteristics were similar for cases and controls (Table 1). There were no age differences by race and financial status. However, older women were more likely to have three or more comorbid conditions, fewer years of education, and a lower body mass index. Upper-Body Limitations After 3 Months ages,, and were between two and three times more likely than controls of the same ages to report limitations in one or more upper-body tasks, adjusting for race, education, financial status, and comorbidity (Table 2). There was only a small difference, however, between cases and controls ages. Although the percentage of cases reporting limitations increased with age, the increase was modest, compared to the nearly twofold increase with age for women without breast cancer. That age by case/ control interaction was statistically significant at/? =.001. We also examined the age-specific, case-control differences in functional limitation for each of the four upper-body tasks (pushing, reaching, heavy lifting, and light lifting). For each task, we found the same general pattern: The casecontrol difference in functional limitation was least pronounced for women in the oldest age group. Upper-Body Limitations After 12 Months We also examined the level of upper-body limitation at 12 months after diagnosis and compared it to upper-body limitation for cases and controls at 3 months. First, however, we examined the characteristics of those women who completed Table 1. Race, Socioeconomic, and Health Variables by Age for and Breast Cancer Detroit Metropolitan Area, 1984-87 Race (% Black) Financial Status (% Not adequate) Education (Mean years) Body Mass Index (Mean kg/m 2 ) Comorbidity (% with 3 + conditions) Age Interaction 18.0 16.5 21.5 19.1 12.8 12.9 26.8 26.7 2.6 1.1 Age 19.3 20.6 17.8 11.9 12.0 27.3 26.9 8.4 5.2 20.9 15.5 17.0 15.6 10.7 10.7 26.7 26.2 10.9 7.2 (n = 267) (n = 274) («= 201) (n = 269) (n = 285) {n = 249) (n = 207) (n = 258) p-value 19.0 16.7 14.5 14.4 10.6 10.3 25.5 25.5 9.6 6.9 Table 2. Percentage of and Breast Cancer with 1 or More Upper-Body Limitations by Age* Control 26.2 21.7 35.0 56.8 Case 58.4 65.8 71.5 71.4 Ratio 2.2 3.0 2.0 1.3.81.72.14.48 <.O2.003 p-value.002.001 'Subjects interviewed at 3 months after diagnosis, adjusted for race, education, financial status, and comorbidity; Detroit metropolitan area, 1984-87. the first but not the second interview. These women were more likely than those who completed both the first and second interviews to be older and Black, and to have had fewer years of education, more comorbid conditions, and inadequate financial resources. More important, those not completing the second interview were more likely to report upper-body limitation at 3 months. However, the characteristics of controls not completing the second interview were very similar to the characteristics of cases not completing the second interview. Consequently, none of the differences between cases and controls was statistically significant. Despite the similar case/control pattern in the characteristics of those interviewed and not interviewed at 12 months,
M218 SATARIANO AND RAGLAND we restricted the sample at 3 months to those cases and controls who also completed the 12-month interview. The level of upper-body limitation at 3 months reported in Table 3 for those who completed both interviews was very similar to that found for all women reported earlier in Table 2. Although there was a statistically significant case/control difference in the percentage of women reporting limitations in one or more upper-body tasks, the magnitude of the case/ control difference was least pronounced for those ages 75-84. The overall test of interaction for age by case/control status was statistically significant at p =.02. This means that the positive association between age and upper-body limitation was more pronounced for controls than for cases. At 12 months after diagnosis, the percentage of breast cancer cases reporting limitations declined, while the percentage of controls with limitations remained largely unchanged (Figure 1). Overall, the case/control differences among women in each age group were much less pro- 100 90 80 70-60 Percent Reporting so Limitation 40. 30 20 10 o Case 65-64 Age Group 25.3 22 8 J8 I Tl Control 231 Hhli 1 31.0 32.8 Age Group 3 Months D12 Months 3 Months D12 Months 62.7 Figure 1. Percentage of breast cancer cases and controls reporting one or more upper-body limitations by age, adjusted for race, education, financial status, and comorbidity, Detroit metropolitan area, 1984-87. nounced than at 3 months, except for ages (Table 3). The percentage of breast cancer patients reporting upperbody limitations was higher with each increase in age, but since this was parallel to that found for controls, no significant age by case/control interaction was found (p =.67). Recuperation Breast cancer patients with limitations at 3 months tended to regain their upper-body strength over the course of the first year. As noted previously, there was little change among controls over the same period (Figure 1). This was reflected in the positive test of interaction for time (3 vs 12 months) by case/control interaction (p <.001). It was also evident that the youngest breast cancer patients (those ages and years) showed the greatest improvement in function. Given that older patients lost less upper-body strength than did younger patients, relative to their agematched controls, we see less improvement in upper-body strength in the older patients (Table 3). This overall pattern of recuperation by age was reflected by the positive test of interaction for time by age by case/control status (p.001). DISCUSSION Assessments of function and "quality of life" have been used increasingly to compare the effectiveness of different treatment protocols for women with breast cancer (4-7). These assessments have also been used to enhance epidemiological studies of breast cancer survival and to provide more detailed information about the need for rehabilitation and home-care services (8-12). Although examinations of quality of life associated with breast cancer have been very useful, most have focused exclusively on women with the disease. As a result, it has Table 3. Percentage of and Breast Cancer with 1 or More Upper-Body Limitations by Age' Age Control Case Ratio p-value 3 Months 12 Months 25.3 31.0 52.7 22.8 23.1 32.8 48.0 Interaction (Time = = 3 Months) Interaction (Time == 12 Months) 55.7 65.8 71.5 71.7 35.1 40.0 53.4 66.3 Interaction (Time = = 3 & 12 Months Combined) Time by Case/Control Status Time by 2.2 3.2 2.3 1.4 1.5 1.7 1.6 1.4 <.OO1.005.02.67.001 "Subjects interviewed at 3 and 12 months after diagnosis, adjusted for race, education, financial status, and comorbidity; Detroit metropolitan area, 1984-87.
UPPER-BODY STRENGTH AND BREAST CANCER M219 been impossible to determine what difficulties are associated with breast cancer and what difficulties are likely to be found among women of the same age without the disease. This is especially problematic in studies of older women, given the high prevalence of age-related functional limitations. It has been difficult, therefore, to address what many consider the key issue in gerontology: distinguishing between the aging process and the disease process (13). Our results confirm previous results that women who survive breast cancer report significant limitations in upperbody strength in the first few months, especially among young women (i.e., under age 75) (1,9). It is not clear why the case-control difference for women 75 and older should be smaller than for younger women. However, a very high percentage of the controls 75 and over report upper-body limitations, suggesting that age processes leading to disability may mask or mimic limitations related to breast cancer. In this way, the case/control design represents an effective strategy for distinguishing between limitations associated with breast cancer and limitations found among women of the same age without the disease. Our results also help to explain why functional limitations associated with cancer are reported to be modest or nonexistent in studies based on prevalent cancer cases; by definition, the length of time since diagnosis will vary among those cases (14). The timing of recuperation, between 3 and 12 months, represents a very encouraging finding for women with breast cancer, although at this point a number of important questions remain unanswered: (a) Does recuperation continue beyond 12 months? (b) Is recuperation a result of physical improvement, or does it reflect success in coping with everyday activities? (c) What are the factors that encourage recuperation? (d) Why are younger women able to regain most of their lost upper-body strength, while older women seemingly do not lose as much function as younger women in the first 3 months after diagnosis? In future case/control studies, we also should develop new strategies to enhance the assessment of upper-body strength. For example, direct assessments of upper-body strength (e.g., as obtained from a hand dynamometer) should be considered. Direct measures are considered to be precise and well suited for detecting changes over time (15). Regarding the timing of assessment, most studies, including the present analysis, are based on interviews conducted at two points in time in this study, at 3 and 12 months after diagnosis. To obtain more precise estimates of functional change, we need to increase the number of assessments. Presently, we do not know when the level of functioning is most likely to change (i.e., the critical transition points). We also do not know how the timing of these transitions varies by the age of the patient. In the future, pilot studies are needed to determine not only what to measure, but when. Research of that kind will make an important contribution to our understanding of the epidemiology of breast cancer survival, as well as the type and timing of rehabilitation services for middle-aged and elderly women. It will also help to better inform patients about what to expect when they undergo treatment for breast cancer. ACKNOWLEDGMENTS This research was supported through a grant from the National Institute on Aging (R01-AG04969), a contract from the National Cancer Institute (N01 CN-55423), and a grant from the American Cancer Society (PBR-67). Address correspondence and reprint requests to Dr. William A. 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