Obesity and Survival to Age 85 Years without Major Disease or Disability in Older Women

Abstract

Context

The impact of obesity on late-age survival without disease or disability in women is unknown.

Objective

To investigate if higher baseline body mass index and waist circumference affects women’s survival to age 85 years without major chronic disease (coronary disease, stroke, cancer, diabetes, or hip fracture) and mobility disability.

Design, Setting, Participants

Examination of 36,611 women from the Women’s Health Initiative who could have reached age 85 years or older if they survived to the last outcomes evaluation on September 17, 2012. Recruitment was from 40 US Clinical Centers from October 1993–December 1998. Multinomial logistic regression models were used to estimate odds ratios and 95% confidence intervals for the association of baseline body mass index and waist circumference with the outcomes, adjusting for demographic, behavioral, and health characteristics.

Main Outcome Measures

Mutually-exclusive classifications: 1) survived without major chronic disease and without mobility disability (“healthy”); 2) survived with ≥1 major chronic disease at baseline, but without new disease or disability (“prevalent diseased”); 3) survived and developed ≥1 major chronic disease but not disability during study follow-up (“incident diseased”); 4) survived and developed mobility disability with or without disease (“disabled”); and 5) did not survive (“died”).

Results

Mean (SD) baseline age was 72.4 (3.0) years (range: 66–81). The distribution of women classified as healthy, prevalent diseased, incident diseased, disabled, and died was 19%, 15%, 23%, 18%, and 25%, respectively. Compared to normal-weight women, underweight and obese women were more likely to die before age 85 years. Overweight and obese women had higher risks of incident disease and mobility disability. Disability risks were striking. Relative to normal-weight women, adjusted odds ratios (95% confidence intervals) of mobility disability was 1.6 (1.5–1.8) for overweight women and 3.2 (2.9–3.6), 6.6 (5.4–8.1), and 6.7 (4.8–9.2), for class I, II, and III obesity, respectively. Waist circumference >88 centimeters was also associated with higher risk of earlier death, incident disease, and mobility disability.

Conclusions

Overall and abdominal obesity were important and potentially modifiable factors associated with dying or developing mobility disability and major chronic disease before age 85 years in older women.

The number of women aged 85 years and older in the United States (US) is growing rapidly, with 11.6 million projected by 2050.¹ Aging without affliction of a major chronic disease or disability is a desired goal for individuals and could ease disability-related health costs, which was approximately 27% of US healthcare expenditures in 2006.²

Obesity prevalence in older US women is also increasing. In 2007–2010, 40% of women aged 65–74 years and 29% of women aged 75 years and older were obese – up by 4% and 5%, respectively, from 2003–2006.³ Obesity is a modifiable risk factor for physical disability^{4, 5} and for many diseases that are highly prevalent in older women, including cardiovascular disease, diabetes, and some cancers.^6–8 Whether obesity affects women’s capacity to reach late adulthood without major disease or disability is unknown. Characteristics associated with healthy survival in older men have been explored in the Honolulu Heart Program/Honolulu Asia Aging Study (HHP/HAAS),^{9, 10} which found greater likelihood of late-age survival without disease and disability among men who were leaner in midlife.^{9, 10} However, studies in older women, who live longer and whose rates of obesity, disease, and disability differ from men, are lacking.

Using an ethnically-diverse population of Women’s Health Initiative (WHI) participants, who could be followed to age 85 years or death, we investigated whether obesity in older women decreased survival to age 85 years without major disease or disability and determined if any risks conferred varied by race/ethnicity and baseline smoking behavior.

METHODS

The study sample was from the WHI Observational Study and Clinical Trial programs, which have been described.^{11, 12} Briefly, postmenopausal women aged 50–79 years were recruited from 40 US clinical centers from October 1993–December 1998. Enrollees participated in one to three clinical trials (CTs) or an observational study (OS). By March 2005, all surviving participants were invited to enroll in the WHI Extension Study for collection of health information beyond 2005. Written informed consent was obtained from all study participants. Procedures and protocols were approved by institutional review boards at all participating institutions.

At enrollment, participants completed standardized questionnaires on demographic characteristics, health behaviors, and medical histories. Race/ethnicity was self-selected as American Indian/Alaskan Native, Asian/Pacific Islander, Black/African American, Hispanic/Latina, White, or Other. Hormone therapy use was self-reported (OS) or based on randomized assignment (CT). Smoking behavior was categorized into never, past, or current use. Alcohol consumption was classified into never, past, light, or moderate-to-heavy drinkers. Physical activity was summarized in metabolic equivalents per week, computed from self-reported duration and frequency of recreational walking or exercise.¹³ Depressive symptoms were assessed using the Burnham adaptation of the Center for Epidemiologic Studies Depression Scale short form.¹⁴

Trained staff measured participants’ height and weight at baseline. Body mass index (BMI) was calculated as weight in kilograms divided by height in meters squared. Using standard World Health Organization (WHO) cut-points⁶, BMI (kg/m²) was categorized as: underweight (<18.5), normal (18.5–<25), overweight (25–<30), obese I (30–<35), obese II (35–<40), and obese III (≥40). Asian/Pacific Islander women were evaluated using WHO cut-points for Asian populations¹⁵: underweight (<18.5), normal (18.5–<23), overweight (23–<27.5), and obese (≥27.5). Waist circumference (WC) was measured during expiration at the narrowest section of the torso and dichotomized at a cut-point of 88 centimeters.⁶

Major chronic diseases included coronary and cerebrovascular disease, cancer (excluding non-melanoma skin cancer), diabetes, and hip fracture. These conditions were selected because they greatly increase a woman’s risk of death and disability and collectively account for a large proportion of later-life morbidity. Disabling diseases, such as arthritis, were captured through identification of impaired mobility. Baseline disease status was self-reported. Incident disease surveillance occurred throughout study follow-up via periodic clinic visits and mailed questionnaires, which occurred biannually for CT women and annually for OS and Extension study participants. Except for diabetes, incident disease was confirmed by physician-adjudicated medical record review. Diabetes was defined by self-reported physician diagnosis of diabetes that included oral medication or insulin treatment.¹⁶

Women who needed crutches, a walker, or a wheelchair to walk on a level surface or who self-reported on the RAND 36-Item Health Survey¹⁷ that their health greatly limited their ability to walk one block or up one were characterized as mobility disabled. For CT participants, assessment of mobility impairment was collected at baseline, in year one of follow-up, and at study close-out. A subsample of CT women completed the assessment every three years from baseline to study close-out. Women in the OS were evaluated three years after baseline and Extension study participants completed assessments annually.

Participant deaths were confirmed by physician adjudication of hospital records, autopsy reports, or death certificates. Periodic checks of the National Death Index for all participants, including those lost to follow-up, were performed.

We identified 43,590 WHI participants who could live to age 85 years by surviving until September 17, 2012, the date when outcomes were last evaluated. Women were classified into mutually-exclusive outcomes, modeled after the HHP/HAAS cohort of older men¹⁰: 1) survived with no major chronic disease or mobility disability (“healthy”); 2) survived with ≥1 major chronic disease at baseline, but did not develop new disease or mobility disability during study follow-up (“prevalent diseased”); 3) survived and developed ≥1 major chronic disease, but not mobility disability during study follow-up (“incident diseased”); 4) survived and developed mobility disability with or without disease (“disabled”); and 5) died before age 85 years. Incident chronic disease and mobility disability was identified before the 85^th birth year.

The potential to live to age 85 years was the study’s only eligibility criterion. However, women who did not provide health information within 18 months of their 85^th birth year (n=5629) and women with baseline mobility disability were excluded (n=1350). Therefore, 36,611 women whose mean (SD) baseline age was 72.4 (3.0) years were analyzed.

Baseline body measures and demographic, behavioral, and health characteristics were compared across the outcomes. Since five nominal outcomes were possible, multinomial logistic regression models were used to examine the association of baseline BMI or WC with the outcomes. Using maximum likelihood, models were simultaneously fit to estimate the odds ratios (ORs) and 95% confidence intervals (CIs) of classification as prevalent or incident diseased, disabled, or died relative to classification as healthy (the referent).¹⁸ All models included baseline age. Fully-adjusted models also included study membership (CT vs. OS), race/ethnicity, education, marital status, and baseline hormone therapy use, smoking status, alcohol use, physical activity, and depression. The correlation between BMI and WC was evaluated. Regression models examining baseline BMI were fit with and without adjustment for WC. Waist circumference models were adjusted for BMI to determine any additional risk conferred by central adiposity. Analyses were repeated after excluding deaths that occurred in the first two years of study follow-up to address potential confounding from underlying illness. Since obesity prevalence varies by race/ethnicity and smoking behavior, stratified analyses were conducted to evaluate the consistency of associations.. All analyses were completed using SAS v9.2 (SAS Institute Inc., Cary, NC).

RESULTS

Among those who survived, 19% (n=6952) were classified as healthy, 14% (n=5366) had prevalent disease, 23% (n=8512) developed incident disease, and 18% (n=6702) were classified as mobility disabled (Table 1). These distributions differed by race/ethnicity and baseline smoking status. The majority (89%) of women were White, 20% of whom were classified as healthy. In contrast, the proportion classified as healthy was 13% for both Black/African American and Hispanic/Latina women. Among current smokers at baseline, 49% died before age 85 years compared to 21% and 27% who were never and past smokers, respectively, at baseline (Table 1).

Table 1.

Baseline Characteristics by Outcomes

Characteristic	Lived to at least age 85 years with:				Did not live to age 85 years
	No disease and No mobility disability	Baseline disease but No incident disease or mobility disability	Incident disease but No mobility disability	Mobility disability with or without disease
No. (%)	6952 (19.0)	5366 (14.7)	8512 (23.3)	6702 (18.3)	9079 (24.8)
Age, mean (SD), y	73.0 (2.9)	73.1 (3.2)	72.4 (3.1)	71.6 (2.7)	72.0 (2.8)
Race/ethnicity, No.(%)
White	6360 (19.6)	4705 (14.5)	7501 (23.1)	5948 (18.4)	7903 (24.4)
Black/African American	271 (12.6)	310 (14.4)	512 (23.8)	381 (17.7)	678 (31.5)
Hispanic/Latina	81 (13.3)	94 (15.5)	140 (23.0)	128 (21.1)	165 (27.1)
Asian/Pacific Islander	144 (18.4)	141 (18.0)	199 (25.4)	127 (16.2)	173 (22.1)
American Indian/Alaskan Native	14 (11.1)	23 (18.3)	24 (19.1)	21 (16.7)	44 (34.9)
Education, No. (%)
<High School	273 (12.0)	318 (13.9)	483 (21.2)	473 (20.7)	736 (32.2)
High School	1173 (17.5)	940 (14.0)	1526 (22.8)	1369 (20.4)	1696 (25.3)
Some College	2668 (18.6)	2039 (14.2)	3385 (23.6)	2648 (18.5)	3577 (25.0)
College Graduate	2804 (21.4)	2034 (15.6)	3057 (23.4)	2179 (16.7)	3007 (23.0)
Family Income, No. (%)
<$20,000	1223 (14.4)	1155 (13.6)	1805 (21.3)	1697 (20.0)	2589 (30.6)
$20,000 to <$50,000	3327 (19.2)	2499 (14.4)	4087 (23.6)	3271 (18.9)	4125 (23.8)
$50,000 or more	1922 (23.8)	1233 (15.2)	2011 (24.9)	1255 (15.5)	1669 (20.6)
Marital Status, No. (%)
Married/Living as married	3734 (19.9)	2744 (14.6)	4565 (24.3)	3588 (19.1)	4182 (22.2)
Widowed	2293 (18.9)	1831 (15.1)	2688 (22.2)	2091 (17.2)	3223 (26.6)
Divorced/Separated	636 (16.0)	539 (13.6)	853 (21.5)	736 (18.5)	1206 (30.4)
Never married	264 (17.2)	225 (14.7)	371 (24.2)	254 (16.6)	420 (27.4)
Hormone Therapy Use, No. (%)
Yes	2847 (19.9)	1978 (13.8)	3339 (23.3)	2803 (19.6)	3358 (23.4)
No	3927 (18.4)	3310 (15.5)	4938 (23.1)	3729 (17.5)	5465 (25.6)
Smoking Behavior, No. (%)
Never Smoked	4099 (20.9)	3026 (15.5)	4743 (24.2)	3629 (18.5)	4090 (20.9)
Past Smoker	2613 (17.7)	2100 (14.3)	3325 (22.6)	2700 (18.3)	4000 (27.1)
Current Smoker	148 (9.0)	138 (8.4)	303 (18.4)	256 (15.6)	798 (48.6)
Alcohol Intake, No. (%)
Non Drinker	722 (16.0)	701 (15.5)	1023 (22.7)	922 (20.4)	1149 (25.4)
Past Drinker	999 (13.7)	988 (13.6)	1589 (21.8)	1456 (20.0)	2249 (30.9)
<1 drink/wk	2145 (18.9)	1619 (14.3)	2706 (23.9)	2201 (19.4)	2662 (23.5)
≥1 drink/wk	3038 (23.1)	2010 (15.3)	3127 (23.8)	2057 (15.6)	2931 (22.3)
Physical Activity, MET-hrs/wk	15.0 (14.5)	13.1 (13.0)	13.4 (13.6)	10.7 (12.3)	10.9 (12.8)
Has Depression, No. (%)
Yes	353 (11.9)	452 (15.2)	560 (18.9)	660 (22.2)	946 (31.8)
No	6404 (19.8)	4724 (14.6)	7675 (23.7)	5801 (17.9)	7799 (24.1)
Weight, mean (SD), kg	66.6 (13.0)	67.4 (14.1)	69.6 (13.9)	75.1 (15.5)	71.4 (16.1)
BMI, mean (SD), kg/m2	26.0 (4.4)	26.2 (4.8)	27.0 (4.9)	29.1 (5.7)	27.7 (5.8)
BMI Category, No. (%)
Underweight (<18.5)	72 (17.1)	76 (18.1)	73 (17.4)	40 (9.5)	159 (37.9)
Normal (18.5–<25)	3077 (23.3)	2314 (17.5)	3138 (23.8)	1587 (12.0)	3085 (23.4)
Overweight (25–<30)	2682 (20.0)	1959 (14.6)	3265 (24.3)	2441 (18.2)	3098 (23.0)
Obese I (30–<35)	849 (13.3)	754 (11.8)	1450 (22.8)	1625 (25.5)	1691 (26.6)
Obese II (35–<40)	158 (7.5)	159 (7.6)	403 (19.2)	698 (33.3)	678 (32.4)
Obese III (≥40)	51 (6.6)	55 (7.1)	115 (14.8)	265 (34.1)	291 (37.5)
Waist Circumference, mean (SD), cm	82.3 (10.7)	83.1 (11.3)	85.7 (12.0)	90.2 (13.5)	87.9 (13.8)
Waist Circumference >88 cm, No. (%)
Yes	1836 (12.9)	1579 (11.1)	3229 (22.6)	3540 (24.8)	4077 (28.6)
No	5090 (22.9)	3769 (17.0)	5260 (23.7)	3144 (14.2)	4946 (22.3)

Abbreviations: MET, metabolic equivalents; BMI, body mass index

Obese women at baseline had a higher proportion of mobility disability by age 85 years (Table 1). While 12% of normal-weight women were classified as disabled by age 85, for women who were obese I, II, and III at baseline, the proportions were 26%, 33%, and 34%, respectively. Similarly, 25% of women with baseline WC >88 cm were categorized as disabled compared to 14% of women with baseline WC ≤88 cm.

Being underweight at baseline was not associated with having prevalent disease or with developing incident disease or a mobility disability by age 85 years (Table 2). However, the adjusted OR (95% CI) of dying before age 85 years was 2.1 (1.5–2.9) for underweight women compared to normal-weight women. Similarly, the risk of earlier death was higher among obese women relative to normal-weight women (Table 2). With an adjusted OR (95% CI) of 1.1 (1.0–1.2) compared to normal-weight women, overweight women also had a higher, albeit moderate risk of death before age 85 years. But, women overweight or obese at baseline had higher risks of developing an incident disease or a mobility disability by age 85 years relative to normal-weight women at baseline. For women who were overweight, obese I, II, and III at baseline, the adjusted ORs (95% CIs) of mobility disability were 1.6 (1.5–1.8), 3.2 (2.9–3.6), 6.6 (5.4–8.1), and 6.7 (4.8–9.2), respectively, relative to normal-weight women at baseline. Women who were obese I at baseline had slightly higher odds of having prevalent disease compared to women normal weight at baseline, otherwise no other differences in the odds of having prevalent disease were observed.

Table 2.

Odds Ratios (95% Confidence Interval) of Outcomes by Baseline BMI and Waist Circumference

	Lived to age 85 years with No disease and with No mobility disability (referent group) relative to:
	Lived to age 85 years with Baseline disease but No incident Disease or mobility disability		Lived to age 85 years with Incident disease but No mobility disability		Lived to age 85 years with Mobility disability, with or without disease		Did not live to age 85 years
	Crudea	Adjustedb	Crudea	Adjustedb	Crudea	Adjustedb	Crudea	Adjustedb
BMI Category
Underweight	1.40 (1.01–1.93)	1.24 (0.87–1.76)	1.03 (0.74–1.43)	0.96 (0.67–1.37)	1.15 (0.77–1.70)	1.11 (0.73–1.70)	2.31 (1.74–3.07)	2.09 (1.54–2.85)
Normal	Ref	Ref	Ref	Ref	Ref	Ref	Ref	Ref
Overweight	0.97 (0.90–1.05)	1.00 (0.92–1.09)	1.19 (1.11–1.28)	1.21 (1.12–1.31)	1.74 (1.60–1.89)	1.64 (1.50–1.79)	1.14 (1.06–1.23)	1.09 (1.01–1.18)
Obese I	1.18 (1.06–1.32)	1.20 (1.06–1.36)	1.65 (1.50–1.82)	1.65 (1.48–1.84)	3.60 (3.24–3.99)	3.22 (2.87–3.61)	1.95 (1.77–2.14)	1.72 (1.55–1.92)
Obese II	1.34 (1.07–1.68)	1.27 (0.99–1.63)	2.44 (2.02–2.96)	2.28 (1.85–2.81)	8.09 (6.73–9.73)	6.62 (5.41–8.09)	4.12 (3.44–4.93)	3.28 (2.69–4.01)
Obese III	1.44 (0.98–2.12)	1.19 (0.79–1.79)	2.11 (1.51–2.94)	1.73 (1.21–2.46)	9.06 (6.66–12.32)	6.65 (4.80–9.21)	5.28 (3.90–7.14)	3.48 (2.52–4.80)
WC > 88 cm
Yes	1.16 (1.07–1.26)	1.12 (1.00–1.26)	1.69 (1.58–1.81)	1.47 (1.33–1.62)	3.07 (2.86–3.31)	1.65 (1.49–1.84)	2.26 (2.11–2.42)	1.83 (1.66–2.03)
No	Ref	Ref	Ref	Ref	Ref	Ref	Ref	Ref

Abbreviations: BMI, body mass index; WC, waist circumference.

^aAdjusted for baseline age only.

^bAdjusted for baseline age, study membership (clinical trial or observational study), baseline hormone therapy use, race/ethnicity, education, marital status, baseline smoking status, baseline alcohol use, baseline physical activity, and baseline depression status. Waist circumference model included adjustment for body mass index.

The correlation coefficient between WC and BMI was 0.8. The ORs for baseline BMI and the outcomes were attenuated, but remained very elevated, when WC was included in the adjustments (Appendix I). Similarly, the adjusted ORs (95% CI) of developing an incident disease or a mobility disability among women with a baseline WC >88 cm, which included adjustment for baseline BMI, were 1.5 (1.3–1.6) and 1.7 (1.5–1.8), respectively, compared to women with baseline WC ≤88 cm. The risk of death before age 85 years was also higher among women with WC >88 cm at baseline relative to women with WC ≤88 cm at baseline (Table 2). Excluding deaths from the first two years of study follow-up (n=532) did not change these findings.

The association between baseline BMI and WC and the outcomes did not vary by baseline smoking status (data not shown). By race/ethnicity, 25%, 44%, 32%, and 7% of White, Black/African American, Hispanic/Latina, and Asian/Pacific Islander women, respectively, were obese (Table 3). Using the WHO cut-points for Asian populations, 17% of Asian/Pacific Islander women were obese. Black/African American women who were overweight or who had a WC >88 cm at baseline and Hispanic/Latina women who were obese at baseline had higher risks of incident disease relative to their White counterparts (Table 3). Likewise, when using the WHO cut-points for Asian populations, the adjusted OR (95% CI) of incident disease before age 85 years was 2.1 (1.3–3.5) for overweight Asian/Pacific Islander women compared to overweight White women (P=0.02) (data not shown).

Table 3.

Adjusted^a Odds Ratios (95% Confidence Intervals) of Outcomes by Race/Ethnicity and Baseline BMI or Waist Circumference

	No. (%)	Lived to age 85 years with No disease and with No mobility disability (referent group) relative to:
		Lived to age 85 years with Baseline disease but No incident disease or mobility disability	Lived to age 85 years with Incident disease but No mobility disability	Mobility disability with or without disease	Did not live to age 85 years
WHITES
BMI Category
Underweight (<18.5)	346 (1.1)	1.15 (0.78–1.72)	1.03 (0.70–1.51)	1.22 (0.77–1.92)	2.27 (1.62–3.18)
Normal (18.5–<25)	11,978 (37.3)	Ref	Ref	Ref	Ref
Overweight (25–<30)	11,954 (37.2)	1.01 (0.92–1.10)	1.18 (1.09–1.28)	1.62 (1.47–1.77)	1.08 (1.00–1.17)
Obese (≥30)	7873 (24.5)	1.19 (1.06–1.35)	1.68 (1.51–1.86)	3.92 (3.51–4.37)	2.05 (1.85–2.27)
WC > 88 cm
Yes	12,425 (38.5)	1.13 (1.01–1.27)	1.44 (1.30–1.59)	1.70 (1.52–1.89)	1.85 (1.67–2.05)
No	19,865 (61.5)	Ref	Ref	Ref	Ref
BLACKS/AFRICAN AMERICAN
BMI Category
Underweight (<18.5)	18 (0.8)	1.08 (0.23–5.10)	0.60 (0.10–3.73)	0.54 (0.05–5.51)	1.07 (0.25–4.61)
Normal (18.5–<25)	403 (18.9)	Ref	Ref	Ref	Ref
Overweight (25–<30)	779 (36.5)	0.97 (0.63–1.51)	1.80 (1.18–2.73)b	1.91 (1.17–3.14)	1.33 (0.89–2.00)
Obese (≥30)	934 (43.8)	1.36 (0.86–2.15)	2.45 (1.58–3.80)	3.80 (2.31–6.24)	2.31 (1.52–3.50)
WC > 88 cm
Yes	1162 (54.2)	1.08 (0.74–1.58)	2.03 (1.44–2.86)b	1.88 (1.29–2.72)	2.28 (1.63–3.19)
No	982 (45.8)	Ref	Ref	Ref	Ref
HISPANIC/LATINO
BMI Category
Underweight (<18.5)	3 (0.5)	-	-	-	-
Normal (18.5–<25)	173 (28.8)	Ref	Ref	Ref	Ref
Overweight (25–<30)	235 (39.2)	1.06 (0.50–2.25)	2.17 (1.05–4.49)	1.74 (0.80–3.81)	0.97 (0.49–1.94)
Obese (≥30)	189 (31.5)	1.35 (0.51–3.56)	4.41 (1.82–10.69)b	5.03 (2.03–12.42)	1.96 (0.84–4.58)
WC > 88 cm
Yes	255 (42.1)	0.86 (0.41–1.79)	1.46 (0.76–2.79)	1.07 (0.55–2.11)	1.29 (0.68–2.46)
No	351 (57.9)	Ref	Ref	Ref	Ref
ASIAN/PACIFIC ISLANDER
BMI Category
Underweight (<18.5)	46 (5.9)	1.34 (0.51–3.51)	0.75 (0.26–2.17)	0.83 (0.23–2.92)	1.48 (0.58–3.82)
Normal (18.5–<25)	445 (57.0)	Ref	Ref	Ref	Ref
Overweight (25–<30)	236 (30.2)	1.06 (0.60–1.87)	1.73 (1.04–2.86)	2.08 (1.18–3.68)	1.29 (0.75–2.21)
Obese (≥30)	54 (6.9)	1.60 (0.43–5.89)	2.21 (0.67–7.32)	4.95 (1.51–16.23)	2.22 (0.66–7.45)
WC > 88 cm
Yes	125 (16.0)	1.35 (0.62–2.91)	2.23 (1.13–4.40)	1.67 (0.79–3.50)	1.46 (0.69–3.07)
No	657 (84.0)	Ref	Ref	Ref	Ref

Abbreviations: BMI, body mass index; WC, waist circumference

^aAdjusted for baseline age, study membership (clinical trial or observational study), baseline hormone therapy use, race/ethnicity, education, marital status, baseline smoking status, baseline alcohol use, baseline physical activity, and baseline depression status. Waist circumference model included adjustment for body mass index.

^bP≤0.05 for effect modification relative to Whites.

COMMENT

This study of older women with a baseline age range of 66–81 years and nearly 19 years of follow-up found that obesity and higher waist circumference were associated with a higher risk of death, major chronic disease and mobility disability before reaching age 85 years. These associations persisted after adjustment for behavioral and socioeconomic risk factors, including physical activity, smoking status, and education.

Women in our study demonstrated prolonged longevity with approximately 75% surviving to age 85 years, nearly one-fifth doing so without mobility disability or a major age-related morbidity defined as a diagnosis of coronary disease, stroke, cancer, diabetes, or hip fracture. In the Cardiovascular Health Study All-Stars study, 63% of 1677 men and women aged 77–102 years had no physical impairment.¹⁹ The Framingham Heart Study of 2531 older adults who could survive to age 85 years reported 36% overall survival and 22% survival without major morbidities including cardiovascular disease, stroke, cancer, and dementia.²⁰ In the HHP/HAAS, 42% of 5820 Japanese-American men survived to age 85 years, 11% without disease and disability.¹⁰

In our study, women with BMI ≥35 kg/m² had over a six-fold higher risk of mobility disability by age 85 years compared to women with BMI 18.5–24.9 kg/m². Remaining mobile substantially impacts quality of life, functional independence, long-term care, and risk of institutionalization.^21–23 Persons with disability utilize more healthcare services and incur an economic burden to society.^{24, 25} In 2006, nearly 27% of total US healthcare costs were spent on disability-related health expenditures.² The population of older women is expected to grow and the prevalence of obesity in this age group continues to rise. Thus, preventing or reducing obesity in older postmenopausal women has important individual, public health, and economic implications on later-life morbidity. There is evidence of successful interventions for weight loss in older obese women, which also demonstrated improvements in cardio-metabolic risk factors.²⁶ The risks and benefits of weight reduction strategies should continue to be researched.

Our association of BMI-defined obesity and increased risk of disability was stronger than in previous studies of older populations.^{5, 27–30} The differences might be because our sample was older and comprised only postmenopausal women and our disability measure primarily focused on impaired mobility. Reuser et al. reported a hazard ratio (95% CI) for disability of 2.8 (2.2–3.6) for women with a BMI ≥35 kg/m² relative to women with a BMI 18.5–24.9 kg/m^2.29 Most published literature, including the Reuser et al. study, characterized disability using measures reflecting severe self-care limitations, rather than measures predominantly related to impaired mobility. Obesity negatively impacts the musculoskeletal system and is an important risk factor for conditions that affect mobility, such as arthritis.³¹ Indeed, a study of 282 older adults showed a seven-fold higher risk of poor overall lower-extremity performance, which included walking and balancing, among persons with a BMI ≥35 kg/m² relative to those with a BMI <24.9 kg/m^2.32 Our definition of disability as a measure of mobility impairment may better reflect obesity-related associations.

We also reported a higher risk of mobility disability among overweight women and those with higher WC. The association between overweight and later-life disability in the literature is mixed. Some reported an increased risk^{5, 29, 30} while others found no relationship.^{4, 27} Diehr et al. reported overweight persons spent more years without an activity of daily living difficulty than normal-weight persons, although findings were less stable in older women than men.²⁸ Studies consistently reported that higher WC was a strong predictor of future mobility disability in older women.^{33, 34}

Obese and overweight women and those with a higher WC also had increased risk of developing coronary disease, stroke, cancer, diabetes, and/or hip fracture before age 85 years. Overall and abdominal obesity are well-established risk factors for many of these age-related chronic diseases.^{7, 8} However, studies in exclusively older populations suggest that the magnitude of the risk might not be as strong as in younger populations. The Cardiovascular Health Study described no differences in the risk of heart attack, stroke, and cancer between overweight, obese, and normal weight among 2752 women aged ≥65 years.³⁵ In another study of 70-year old women, obesity was not associated with incident coronary disease³⁶ and stroke.³⁷ Folsom et al. identified a weak increased risk of incident cancer in obese women only, but a protective dose-response relationship for BMI and WC with hip fracture incidence.³⁸ In contrast, studies consistently reported a strong association between higher BMI and WC and increased diabetes risk.^{35, 38–40} To complicate matters, many older people have multimorbidities.⁴¹ Our results suggested overweight and obesity were associated with an increased risk of developing chronic disease in late-life. However, we found a weak association between BMI and survival to age 85 years among women with major chronic disease at baseline but who did not develop any new morbidity during follow-up. These women were demographically similar to the healthy survival group. This could be explained by self selection. Women who entered the study with prevalent disease may be less impacted by their disease history than women with these diseases who elected not to join the study. In this study, we did not delineate type, duration, severity or number of diseases, nor did we examine characteristics associated with disease management, which are important considerations but not within the scope of this paper. Of note, women characterized as “healthy” in our study were not necessarily disease-free and might have had health conditions that did not cause mobility disability but were not considered, such as eye diseases.

Our results revealed a J-shaped relationship between BMI and mortality. This observation is consistent with the published literature,^{27, 42–45} and suggests further consideration of “healthy weight” ranges and appropriate weight reduction goals for overweight older people.^{35, 46} Debate persists about the appropriate definition of obesity for older adults.^46–49 Waist circumferences may better represent excess abdominal fat in older people.^{49, 50} Yet, literature on WC and mortality in older populations is mixed. In a study of women aged 55 years and older, only those in the highest quintile of WC (>96 cm) had an increased all-cause mortality risk, although their estimations did not adjust for BMI.³⁸ However, women aged 50 years and older with a WC >75 cm were shown to have a higher BMI-adjusted risk of all-cause mortality, with risks increasing further as WC increased.⁵¹ We observed an increased risk of death before age 85 years in women with WC >88 cm that was independent of BMI, suggesting that both BMI and WC may be important determinants of mortality in older women.

Underweight women in our study were at increased risk of death before age 85 years, but only represented 1.2% of our population. Hypotheses regarding the increased mortality risk in underweight women include malnutrition, frailty, and underlying disease or disability.⁴³ Studies often exclude data from the first few follow-up visits to account for this possible confounding,^{27, 43, 44, 49} but sensitivity analyses that excluded earlier deaths did not change our results.

Compared to normal-weight women of the same race/ethnicity, Black/African American women who were overweight and Hispanic/Latina women who were obese at baseline had higher risks of developing a major chronic disease by age 85 years than White women. In addition, Black/African American women with higher WC relative to those with lower WC had a higher risk of incident disease before age 85 years than White women. Research examining differences by race/ethnicity in the association of BMI to risk of late-life disease in older women is limited. However, studies consistently report that these minority groups have disproportionately higher rates of overweight and obesity^{3, 52, 53} as well as higher rates of major chronic diseases, including diabetes^{54, 55}, cardiovascular disease^56–58, and cancer.^59–61 Debate continues about whether the standard WHO definitions for overweight and obesity are appropriate for Asian populations.^{15, 62} Reanalysis using WHO cut-points for Asian populations¹⁵ suggested that overweight Asian/Pacific Islander women also had a higher risk of incident disease by late age compared to overweight White women. Confirmation in larger samples is needed, but standard WHO cut-points may underestimate disease risk for Asian/Pacific Islander women.

This study has limitations. WHI participants may have been healthier at baseline than their age counterparts in the general population. However, strong associations of body size with the outcomes were still observed. We did not include all forms of disability, such as sensory or cognitive impairment. Yet, our focus on mobility disability acknowledged the importance of maintaining the ability to walk in healthy aging and a strong link to obesity was described. Finally, we did not consider body size changes over time, which increases during the midlife but is variable in older ages.^{63, 64} These anthropometric changes are likely to affect health and survival in later ages but the temporality of these changes is complex and beyond the scope of this study.

The large, diverse sample of older women, high retention and outcome ascertainment rates, and the availability of adjudicated outcomes for major diseases were study strengths. Body size measures were clinically measured and included waist circumference. Our analyses included nearly 19 years of follow-up data from a prospective cohort study design that included women who died before age 85 years, which cannot be captured in de novo studies of exceptional agers.

CONCLUSION

Having a healthy body mass index or waist circumference was associated with a higher likelihood of surviving to older ages without a major disease or mobility disability. In contrast, higher body mass index and waist circumference was associated with an increased risk of death before reaching age 85 years and with late-age survival with incident disease and mobility disability. Obese women, in particular, had an increased risk of developing a mobility disability by age 85 years. Successful strategies aimed at maintaining healthy body weight, minimizing abdominal fat accretion, and guiding safe, intentional weight loss for those who are already obese should be further investigated and disseminated.