Racial disparities in functional disability among older women with newly diagnosed nonmetastatic breast cancer

Authors

  • Cynthia Owusu MD, MS,

    1. Division of Hematology/Oncology, Department of Medicine, Case Western Reserve School of Medicine, Cleveland, Ohio
    2. Case Comprehensive Cancer Center, Cleveland, Ohio
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  • Mark Schluchter PhD,

    1. Case Comprehensive Cancer Center, Cleveland, Ohio
    2. Department of Epidemiology and Biostatistics, Case Western Reserve School of Medicine, Cleveland, Ohio
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  • Siran M. Koroukian PhD,

    1. Case Comprehensive Cancer Center, Cleveland, Ohio
    2. Department of Epidemiology and Biostatistics, Case Western Reserve School of Medicine, Cleveland, Ohio
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  • Suzanne Mazhuvanchery BS,

    1. Division of Hematology/Oncology, Department of Medicine, Case Western Reserve School of Medicine, Cleveland, Ohio
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  • Nathan A. Berger MD

    Corresponding author
    1. Division of Hematology/Oncology, Department of Medicine, Case Western Reserve School of Medicine, Cleveland, Ohio
    2. Case Comprehensive Cancer Center, Cleveland, Ohio
    • Corresponding author: Cynthia Owusu, MD, MS, Case Western Reserve University, UHHS Seidman Cancer Center-BHC 5055, 11100 Euclid Avenue, Cleveland, OH 44106-5055; Fax: (216) 844-5234; Cynthia.owusu@case.edu

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Abstract

BACKGROUND

This study sought to assess racial differences in functional disability among older women with nonmetastatic breast cancer.

METHODS

In this cross-sectional study, between April 2008 and December 2012, women aged ≥ 65 years with newly diagnosed stage I through III breast cancer were recruited from ambulatory oncology clinics at an academic center. Prior to receiving any adjuvant treatment, participants completed a comprehensive geriatric assessment. The primary outcome was functional disability, defined as dependency in any basic or instrumental activity of daily living, categorized as “yes” or “no.” Logistic regression analyses were undertaken.

RESULTS

The study enrolled 190 women whose mean age was 75.0 years at diagnosis (standard deviation=7.0, range=65-93 years). Thirty-two percent were African American (AA), and 39% had functional disability. Controlling for age, participants with functional disability were more likely to be AA (versus non-Hispanic white), odds ratio=4.19, 95% confidence interval=2.12-8.27. Fifty-nine percent of the racial difference in functional disability was explained by a higher prevalence of lower income and education among AAs. In addition, the higher prevalence of chronic medical conditions and obesity among AAs, after accounting for socioeconomic factors, further explained 40% of the black–white difference in functional disability.

CONCLUSIONS

Among older women with newly diagnosed nonmetastatic breast cancer, functional disability is highly prevalent, and AAs are disproportionately affected. Interventions to optimize the functional status of at-risk individuals, particularly AAs, during and after cancer treatment may improve treatment tolerance and overall survival outcomes. Cancer 2013;119:3839–3846. © 2013 American Cancer Society.

INTRODUCTION

The elimination of health disparities is a major public health priority. With increasing age, chronic medical conditions become more common. The burden of illness, however, is not shared equally among all racial/ethnic groups. African American (AA) individuals have a higher prevalence of heart disease,[1] diabetes,[2] and hypertension,[3] compared with non-Hispanic whites. In addition, many chronic medical conditions are associated with a considerable amount of difficulties with activities of daily living (ADLs) resulting in functional disability. An abundance of research has shown racial differences in the prevalence and incidence of age-related functional disability, with AAs being 3 times as likely to experience functional disability compared with non-Hispanic whites.[4, 5] However, over the past decade, despite improving trends in disability rates, little progress has been made, and AA individuals continue to exhibit higher rates of functional disability compared with non-Hispanic whites.[6] Evidence suggests that the association between race and functional disability might be explained by a higher prevalence of lower socioeconomic status (SES), obesity, smoking, alcohol intake and chronic disease such as heart and cerebrovascular disease in the AA population.[7]

Although racial disparities in late-life functional disability have been well documented in older adults in general,[8, 9] to the best of our knowledge, such disparities and its clinical implications have not been examined among older adults with cancer. Cancer is associated with an increased risk of functional limitations and decline. Compared with their noncancer counterparts, cancer survivors are more likely to experience steeper functional decline[10] and twice as likely to experience functional limitations.[11] In addition, among older women with early stage breast cancer, persistent decline in physical functioning has been found to be associated with an increased mortality risk.[12] Given the higher prevalence of functional disability and decline among patients with cancer, it is important to know if racial differences in functional disability are prevalent in the geriatric-oncology population because this may have clinical implications for appropriate targeting of interventions. As the population in the United States ages and becomes increasingly more diverse, the unmet needs of older racial minorities will become even more critical. Older adults are projected to compose 20% of the population by 2030,[13] with the most rapidly growing racial/ethnic groups projected to be AAs and Hispanics.[14] The changing racial/ethnic composition of the aging population has been hypothesized as contributing to the worsening trends in disability rates among older adults aged 60 to 69 years.[6]

Identifying at-risk groups for functional disability in the geriatric-oncology population is of paramount importance to inform appropriate treatment decision-making, and to appropriately target interventions for supporting such patients through treatment. Ultimately, such interventions could lead to improved functional status and overall survival. The primary objective of this study, therefore, was to assess for racial differences in functional disability among older women with nonmetastatic breast cancer. We hypothesized that compared with non-Hispanic white women, AA women with newly diagnosed stage I through III breast cancer will be more likely to exhibit functional disability at diagnosis. A secondary objective was to identify patient factors that were independently associated with functional disability and also explained the racial differences in functional disability.

MATERIALS AND METHODS

Study Design and Patient Population

This is a cross-sectional study of patients aged 65 years and older with newly diagnosed histologically confirmed stage I through III breast cancer. Patients were recruited from ambulatory oncology clinics at an academic center between February 1, 2008, and December 31, 2012. Patients were excluded from the study if prior to enrollment they had received chemotherapy, hormonal therapy, targeted therapy, or breast irradiation for the current diagnosis of breast cancer. Receipt of primary breast surgery before (adjuvant setting) or after enrollment (neoadjuvant setting) was allowed. AAs were oversampled. The study was approved by the Institutional Review Board of the University Hospital Case Medical Center.

Study Procedures and Data Collection

Through use of a weekly multidisciplinary breast cancer conference list, potentially eligible patients were identified and screened. Patients satisfying eligibility criteria were then approached for informed consent by a research assistant during patients' initial visit with a medical or radiation oncologist. Patients who provided informed consent completed a comprehensive geriatric assessment. In addition, participants completed a questionnaire that captured data on sociodemographic variables (age, race, educational and marital status, living situation, and annual income). Data on median household income was obtained from United States Census Bureau Web site[13] using participants' ZIP codes from their place of residence at the time of enrollment. Data on comorbidities, concomitant medications, tumor characteristics, and cancer treatments received was abstracted from medical records. In total, 581 patients were screened using the multidisciplinary breast cancer tumor board list, of whom 506 (87%) were identified as being potentially eligible. Of the 506 patients, 245 (48%) were approached for informed consent, of whom 190 (77%) agreed to study participation and 55 (23%) declined study participation. Compared with non-Hispanic whites, AAs were more likely to be approached for study consent (65% versus 44%, P = 0005). This can be explained by the oversampling of AA individuals. There was no statistically significant difference in the proportion of patients; approached for consent by age group (< 75 versus ≥ 75 years [48% versus 49%, P = 94]). With regard to patients who were approached, there was no statistically significant difference in those who declined participation by race (AAs versus non-Hispanic whites [27% versus 33%, P = 40]) or by age group (< 75 versus ≥ 75 years [28% versus 34%, P=.40]). Reasons for not approaching patients for consent included ineligibility (39%), sites located more than a 20-mile radius from the main academic center and simultaneous office visits that made it logistically impossible to approach (42%), physician request not to approach patient (3%), medical illnesses precluding study participation, eg, acute illness (6%), and no follow-up with medical or radiation oncology after breast surgery (10%).

Measures

Self-reported functional status was evaluated using the Katz ADLs, and the Lawton's Instrumental ADLs (IADLs). Although ADLs are necessary skills for basic living, IADLs are the skills required for living independently in the community. ADLs measure self-reported dependence or nondependence with bathing, transfer, dressing, continence, toileting, and feeding,[15] and IADLs measure dependence or nondependence with shopping, using the telephone, managing medications, housekeeping, laundry, transportation, ability to manage finances, and preparing meals.[16] Evaluations of falls relied on participants' self-report of the number of falls in the last 6 months. The Mini-mental State Examination (MMSE) was used to screen for cognitive impairment,[17] and the Geriatric Depression Scale (GDS)[18] was used to screen for depression.

Comorbidities and Review of Medications

Comorbidity data was abstracted from medical records and supplemented with self-report of medical problems by participants at study entry. Using this information, we derived the Charlson Comorbidity Index[19] score, based on the presence or absence of 18 medical conditions. A medication review of all prescribed medications was conducted for all participants by relying on participants' self-report and a review of medical records. Using the medication count, we defined polypharmacy as the concurrent use of 5 or more prescribed medications.[20]

Analytic Variables

Primary outcome variable

The primary outcome variable was functional disability at baseline dichotomized as having at least 1 dependency in ADL/IADLs (as “yes” or “no”).

Independent variable

The independent variable was race dichotomized as non-Hispanic white versus AA. No other race was reported by participants.

Explanatory variables

Explanatory variables included age (65-74 years, ≥ 75 years); marital status (married, other); educational status (≤ high school, > high school); median household income (≥ $65,000, $50,000 to < $65,000, $35,000 to < $50,000, < $35,000). Median household income was also dichotomized as < $35,000 (lowest quartile) versus ≥ $35,000; living situation (alone, other); body mass index (BMI) < 25 kg/m2, 25 kg/m2, to ≤ 30 kg/m2, ≥ 30 kg/m2, and also as a continuous variable; stage (I-II, III); primary breast surgery (mastectomy, lumpectomy, none); setting within which baseline assessment was completed (neoadjuvant, adjuvant treatment); and comorbidity (Charlson Comorbidity Index score of 0-1, ≥ 2). In addition, we examined the association between select comorbid conditions and functional disability and dichotomized the following variables as “yes” or “no,” based on their presence: diabetes mellitus, coronary artery disease, congestive heart failure, cerebrovascular accident, chronic obstructive pulmonary disease, chronic kidney disease, and arthritis. Similarly, we dichotomized geriatric syndromes (dementia, depression, falls, and polypharmacy) as “yes” or “no.”

Data Analysis

To examine how baseline characteristics differed by race, we conducted bivariate analyses of all baseline variables by race. The chi-square test or Fisher's exact test, when appropriate, was used to determine if a statistically significant difference existed in the distribution of baseline characteristics between the 2 groups. Logistic regression was used to examine the relation of race to the odds of functional disability. We developed our multivariable model by first identifying baseline characteristics that were significantly associated with functional disability at P < .10 on bivariate analysis. Our final multivariable logistic regression model included variables that remained significant at P < .05. To identify baseline characteristics that might explain the relation between race and functional disability, we used an extended-model approach for covariate adjustment: model 1=race and age; model 2=model 1 + SES factors (median household income and educational status); model 3=model 2 + comorbidity; model 4=model 3 + BMI. The percent reduction in excess of odds of functional disability in AAs explained by adjusting for a factor such as educational status was calculated as 100× [OR(unadjusted) − OR(adjusted)]/[OR(unadjusted) − 1], where OR(unadjusted) and OR(adjusted) are the odds ratios in the models without and with adjustment for education, respectively.[21] Finally, we conducted sensitivity analyses by excluding participants who received neoadjuvant treatment from the cohort, leaving us with the subcohort who underwent study procedures in the adjuvant setting (146 patients). All P values presented are 2-sided. All analyses were conducted using SAS version 9.2 (SAS Institute, Cary, NC).

RESULTS

Subjects' Baseline Characteristics

Baseline characteristics are displayed in Table 1. Study enrollment consisted of 190 participants with stage I through III breast cancer. The median duration from diagnosis to baseline assessment was 2.1 months (interquartile range, 1.3-3.0 months). The median age was 74 years (range, 65-93 years), 32% were AA, and 46% had education level of high school or less.

Table 1. Baseline Characteristics of Participants
Baseline CharacteristicsN = 190 (100%)
  1. a

    Median household income is derived from information from the US Census Bureau, through use of ZIP codes.

  2. b

    Functional disability denotes self-reported ADL/IADL (activities of daily living/instrumental activities of daily living) dependence.

Age group (y)
65 to 74102 (54%)
≥7588 (46%)
Race
African American60 (32%)
Non-Hispanic white130 (68%)
Educational status
High school or less87 (46%)
More than high school103 (54%)
Marital status
Married69 (36%)
Other121 (64%)
Median household incomea
≥$65,00050 (26%)
$50,000 to <$65,00060 (32%)
$35,000 to <$50,00037 (19%)
<$35,00043 (23%)
Living situation
Alone80 (42%)
Other109 (58%)
Missing/unknown1
Body mass index
<2548 (25%)
25 to ≤3058 (31%)
≥3084 (44%)
Stage
Stage I-II165 (88%)
Stage III23 (12%)
Unknown2
Primary surgery
Mastectomy51 (28%)
Lumpectomy120 (65%)
None14 (8%)
Missing/pending5
Primary surgery prior to enrollment
Yes146 (77%)
No44 (23%)
Chemotherapy
Yes45 (24%)
No139 (76%)
Missing/unknown6
Functional disabilityb
No116 (61%)
Yes74 (39%)
Charlson Comorbidity Index
0-1143 (75%)
≥ 247 (25%)
Select chronic medical conditions
Hypertension147 (77%)
Diabetes mellitus45 (24%)
Coronary artery disease27 (14%)
Congestive heart failure11 (6%)
Cerebrovascular accident12 (6%)
Chronic pulmonary airways disease27 (14%)
Chronic kidney disease12 (6%)
Arthritis90 (47%)
Geriatric syndromes
Depression16 (8%)
Polypharmacy (≥5 concomitant medications)94 (50%)
Dementia8 (4%)
Falls (≥2 in 6 months)13 (7%)

Subjects' Baseline Characteristics According to Race

The relation between race and baseline characteristics is displayed in Table 2. AA individuals were more likely than non-Hispanic whites to have high school or less education (60% versus 39%, P=.008); to have median household income in the lowest quartile (58% versus 6%, P < .0001); not to be married (77% versus 58%, P = .01); to be obese (52% versus 40%, P = .03); to have functional disability (62% versus 28%, P < .0001); and to have a Charlson Comorbidity Index score ≥ 2 (42% versus 17%, P=.0002). With regard to the prevalence of chronic medical conditions and geriatric syndromes at baseline (data not shown), AA individuals were more likely to have hypertension (93% versus 70%, P=.0004); to have diabetes mellitus (38% versus 17%, P =.001); to have congestive heart failure (12% versus 3%, P=.04); and to have chronic kidney disease (13% versus 3%, P=.02). There were no statistically significant black–white difference in the prevalence of any of the 4 geriatric syndromes, and as such, based on our data, none of the geriatric syndromes could mediate the relation between race and functional disability.

Table 2. Baseline Characteristics According to Race
CharacteristicAfrican Americans 60 (32%)Non-Hispanic Whites 130 (68%)P
  1. P values in bold denote statistically significant.

Age group (y)
65 to 7429 (48)73 (56) 
≥7531 (52)57 (44).32
Educational status
High school or less36 (60)51 (39) 
More than high school24 (40)79 (61).008
Median household income   
≥$65,0005 (8)45 (35) 
$50,000 to <$65,0009 (15)51 (39) 
$35,000 to <$50,00011 (18)26 (20) 
<$35,00035 (58)8 (6)<.0001
Marital status
Married14 (23)55 (42) 
Other46 (77)75 (58).01
Living situation   
Alone28 (47)52 (40) 
Other32 (53)77 (60).41
Body mass index
<258 (13)40 (31) 
25 to ≤3020 (33)38 (29) 
≥3032 (53)52 (40).03
Stage
Stage I-II49 (82)116 (91) 
Stage III11 (18)12 (9).08
Primary surgery
Mastectomy18 (32)33 (26) 
Lumpectomy35 (61)85 (67) 
None4 (7)8 (6).72
Primary surgery before enrollment   
No19 (32)25 (19) 
Yes41 (68)105 (81).06
Functional disability
Yes37 (62)37 (28) 
No23 (38)93 (72)<.0001
Charlson Comorbidity Index
0-135 (58)108 (83) 
≥225 (42)22 (17).0002

Subjects' Baseline Characteristics According to Functional Disability

The prevalence of functional disability at enrollment was high (39%). Table 3 presents unadjusted analysis to identify baseline characteristic associated with functional disability. Compared with non-Hispanic whites, AAs were more likely to have an increased odds of functional disability at baseline (OR=4.04, 95% CI=2.12-7.01).

Table 3. Univariate Analysis Showing Clinical Factors Associated With Functional Disability at Baseline Among Older Women With Breast Cancer
Baseline CharacteristicsOdds Ratio95% Confidence IntervalP
Age group (y)   
65 to 74Referent  
≥753.511.90, 6.47<.0001
Race   
WhiteReferent  
African American4.042.12, 7.01<.0001
Educational status   
More than high schoolReferent  
High school or less4.162.20, 7.86<.0001
Median household income   
≥$35,000Referent  
<$35,000 (Lowest Quartile)4.702.27, 9.72<.0001
Marital status   
MarriedReferent  
Other1. 460.79, 2.70.23
Living situation   
OtherReferent  
Alone0.890.49, 1.60.69
Body mass index   
I unit1.041.00, 1.09.07
Stage   
Stage I-IIReferent  
Stage III2.220.92, 5.36.08
Primary surgery before enrollment   
YesReferent  
No2.041.03, 4.04.04
Charlson Comorbidity Index   
0-1Referent  
≥23.971.99, 7.94<.0001

Race and Functional Disability

The independent association between race and functional disability at baseline is displayed in Table 4. Accounting for age (model 1), AA women relative to non-Hispanic whites had an increased odds of reporting functional disability at baseline, (OR=4.19, 95% CI=2.12-8.27). Further adjustment for differences in educational status and median household income (model 2), diminished the racial disparity in functional disability by 59% but did not completely eliminate the black–white difference in functional disability at baseline (OR=2.31, 95% CI=1.00-5.41). Median household income was the more robust mediator and alone explained 54% of the excess odds of functional disability due to race, whereas educational status alone explained 17% of the excess odds of functional disability due race. In model 3, after adjusting further for chronic medical conditions as measured with the Charlson Comorbidity Index, the black–white difference was further diminished by 33%. Notably, accounting further for differences in chronic medical conditions completely eliminated any statistically significant black–white difference in functional disability, although the magnitude of the odds of AA individuals having functional disability remained high (OR=1.88, 95% CI=0.78-4.53). Because the influence of SES on functional disability may overlap with chronic medical conditions, we also tested a model that only included chronic medical conditions without income and education and found that 22% of the excess of the odds of functional disability in AAs was due to chronic medical conditions. Finally, adjusting the model by including BMI (model 4) further attenuated the odds of AAs having functional disability by a modest amount (OR=1.79, 95% CI=0.73-4.39), with BMI explaining 10% of the excess odds of functional disability due to race. Together, socioeconomic factors, chronic medical conditions, and increasing BMI explained 75% of the excess odds of functional disability between AAs and non-Hispanic whites. All mediating factors were independently associated with functional disability (model 4).

Table 4. Association Between Race and Functional Disability at Baseline Among Older Women With Breast Cancer and the Mediating Effect of Clinical Factors on the Relationship Between Race and Functional Disability
 Functional Disability at Baseline Odds Ratio (95% Confidence Interval)
VariablesModel 1Model 2Model 3Model 4
Race    
WhitesReferentReferentReferentReferent
Blacks4.19 (2.12, 8.27)2.31 (1.00, 5.41)1.88 (0.78, 4.53)1.79 (0.73, 4.39)
Age group (y)    
65 to 74ReferentReferentReferentReferent
≥753.63 (1.90, 6.95)3.39 (1.71, 6.74)3.08 (1.53, 6.22)3.80 (1.79, 8.06)
Educational status    
More than high school ReferentReferentReferent
High school or less 3.37 (1.71, 6.64)3.56 (1.77, 7.16)3.54 (1.75, 7.16)
Median household income    
≥$35,000 ReferentReferentReferent
<$35,000 (Lowest Quartile) 2.61 (1.00, 6.83)2.61 (1.00, 6.98)2.77 (1.02, 7.53)
Charlson Comorbidity Index Score    
0-1  ReferentReferent
≥2  2.87 (1.29, 6.40)2.60 (1.16, 5.85)
Body mass index    
1-unit increase   1.05 (1.00, 1.11)

We enrolled participants in both the neoadjuvant and adjuvant setting. Compared with participants enrolled in the adjuvant setting, those enrolled in the neoadjuvant setting were more likely to be AA versus non-Hispanic white (32% versus 19%, P=.06) and to have stage III disease versus stage I or II (65% versus 17%, P < .0001) (data not shown). We conducted sensitivity analyses in the adjuvant group to determine if conclusions from this subgroup were any different from conclusions reached within the entire cohort (data not shown). Within the subgroup of participants enrolled in the adjuvant setting, participants with functional disability were more likely to be AA (versus non-Hispanic whites) (OR=2.93, 95% CI=1.26-6.85); to have education of high school or less (versus more than high school education) (OR=3.03, 95% CI=1.38-6.34); and to be ≥ 75 years of age (versus < 75 years) (OR=3.33, 95% CI=1.53-7.25). Our conclusion from the entire cohort that AA individuals were disproportionately affected by functional disability was therefore not different in the subgroup analyses.

DISCUSSION

This study examined racial disparities in functional disability among older women with newly diagnosed nonmetastatic breast cancer and identified patient factors that might explain such differences. The study found that relative to non-Hispanic whites, older AA women were nearly 2 times more likely to experience functional disability at diagnosis of stage I through III breast cancer. In addition, the study found that although the racial difference in functional disability was partly explained by differences in median household income, educational status, chronic medical conditions, and obesity, residual racial differences in functional disability remained after accounting for these factors. Finally, the study found that being aged 75 years and older, having lower income and educational status, increasing BMI, and having multiple chronic medical conditions were all patient factors that independently increased the odds of being dependent in ADLs among older women with newly diagnosed stage I through III breast cancer.

In the United States, racial and ethnic minorities and persons with lower SES have persistently exhibited poorer health status and higher rates of functional disability, morbidity, and mortality.[4, 22, 23] Although rates of late-life functional disability have been declining since the early 1980s with steeper declines in the late 1990s, at every level of the disablement process, blacks are at a considerable disadvantage. Fuller-Thomson et al[21] in a study of more than 16,000 older non-Hispanic blacks and more than 180,000 non-Hispanic whites found that black women aged 65 to 74 years were more than twice as likely to report functional disability. Our study findings are therefore consistent with previous work conducted among older adults in general and further extend the existing literature by demonstrating that black–white differences in functional disability are prevalent among older women with newly diagnosed stage I through III breast cancer.

Our study identified a higher prevalence of 2 patient factors among AAs, notably lower SES and chronic medical conditions including obesity, which partly contributed to the black–white difference in functional disability. Although the precise causal pathways leading to racial differences in functional disability remain to be clearly delineated, SES may be the primary underlying link tying together race, chronic medical conditions, and functional disability. Lower SES may lead to a higher prevalence of chronic medical conditions and functional disability through complex pathways that involve behavioral, psychological, social, and biological factors. For example, compared with persons with higher SES, those with lower SES are more likely to be active smokers,[24] less likely to engage in physical activity,[25] and more likely to be obese,[26] and therefore more likely to develop chronic medical conditions such as hypertension and diabetes mellitus. Once disease is established, individuals with lower SES due to their limited resources are more likely to face challenges with access to health care, leading to late diagnosis of disease and ultimately leading to long-term complications and functional disability. Indeed, several studies have demonstrated that SES either fully explains or partly explains racial differences in health status, including functional disability. Fuller-Thomson et al[21] demonstrated that among women aged 65 to 74 years, approximately 50% of the excess in functional disability associated with being black was explained by educational status and household income. Whitson et al[27] extended this work further and identified obesity and diabetes mellitus as accounting for 30% of the black–white difference, after differences in sociodemographic factors had been accounted for.

Despite the role of SES and health conditions in partly explaining the black–white differences in functional disability in our study, residual racial differences in functional disability remained after accounting for these factors. The magnitude of the residual black–white difference in functional disability after adjusting for sociodemographic factors and chronic medical conditions was almost double. This large residual difference in functional disability would have been statistically significant if we had a larger sample size and therefore deserves comment. Smoking and physical activity, as previously discussed, are important factors that contribute to an individual's health status. Our study did not collect data on smoking status or physical activity, and therefore differences in these 2 factors could not be accounted for in our models. Other limitations of the study include the cross-sectional study design which precludes any conclusions regarding causality, selection bias which could have resulted from oversampling of AA individuals, the setting of the study which is a single-site academic institution with a patient population that may not be reflective of the general population of older women with breast cancer, and self-identification of racial status which may underreport mixed race. Regardless of these limitations, our study findings are consistent with the existing literature.

Our study findings have clinical implications that pertain to the management of older cancer patients. At-risk groups for functional disability, such as older AAs may be less likely to tolerate standard treatment. Moreover, such individuals are more likely to experience persistent functional decline after treatment, further worsening their survival outcomes. Although still requiring a larger clinical trial for validation, interventions that target at-risk individuals (such as AAs) during and after cancer treatment could improve functional status, minimize treatment toxicity, and improve overall survival outcomes. In addition, functional disability exacts a huge financial burden both on a personal level and on the health care system. For patients with cancer who have functional disability, the financial burden due to cancer diagnosis and treatment is further compounded by the financial burden from functional disability and may lead to significant financial hardship and limit access to care.

In conclusion, functional disability is highly prevalent among older women with newly diagnosed nonmetastatic breast cancer, and AAs are disproportionately affected. Lower SES, obesity, and poor health status all appear to contribute to the racial gap in functional disability. Given that functional disability has enormous public health consequences, including increased health care use and costs[28, 29] and increased mortality,[30] and given the importance of functional status in cancer treatment decision-making and treatment tolerance, interventions to improve functional status, particularly among older AAs with newly diagnosed stage I through III breast cancer, are warranted. Such interventions will need to be sensitive to racial disparities in SES, obesity, and chronic medical conditions, if they are to be successful.

FUNDING SOURCES

This study was supported in part by a Susan Komen Breast Cancer Foundation Career Catalyst in Disparities Research Grant (KG100319) to Cynthia Owusu, MD, and in part, by pilot funding to Cynthia Owusu, MD from the Cancer and Aging Research Program Development Grant (P20 CA103767, Nathan Berger, MD, Principal Investigator).

CONFLICT OF INTEREST DISCLOSURE

Dr. Schluchter had been a consultant (scientific reviewer) for the Komen Foundation. Dr. Koroukian has received fees for participating in NIH study section meetings, and has a spouse who serves as director of and has stock options in American Renal Associates.

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