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Original Research |

Obesity, Race, and Risk for Death or Functional Decline Among Medicare Beneficiaries: A Cohort Study

Christina C. Wee, MD, MPH; Karen W. Huskey, MPH; Long H. Ngo, PhD; Angela Fowler-Brown, MD, MPH; Suzanne G. Leveille, RN, PhD; Murray A. Mittlemen, MD, DrPH; and Ellen P. McCarthy, PhD, MPH
[+] Article and Author Information

From Beth Israel Deaconess Medical Center, Harvard Medical School, and University of Massachusetts Boston, Boston, Massachusetts.


Disclaimer: The results, findings, and interpretation presented in this article are those of the authors and do not represent the views of Centers for Medicare & Medicaid Services or the National Institutes of Health.

Acknowledgment: The authors thank the Centers for Medicare & Medicaid Services for providing the initial data.

Grant Support: By the National Institute of Diabetes and Digestive and Kidney Diseases (R01 DK071083).

Potential Conflicts of Interest: Disclosures can be viewed at www.acponline.org/authors/icmje/ConflictOfInterestForms.do?msNum=M10-1794.

Reproducible Research Statement:Study protocol, statistical code, and data set: Not available.

Requests for Single Reprints: Christina C. Wee, MD, MPH, Division of General Medicine and Primary Care, Beth Israel Deaconess Medical Center, 330 Brookline Avenue, Boston, MA 02215; e-mail, cwee@bidmc.harvard.edu.

Current Author Addresses: Drs. Wee, Ngo, Fowler-Brown, Leveille, Mittlemen, and McCarthy and Ms. Huskey: Beth Israel Deaconess Medical Center, 330 Brookline Avenue, Boston, MA 02215.

Author Contributions: Conception and design: C.C. Wee, E.P. McCarthy.

Analysis and interpretation of the data: C.C. Wee, K.W. Huskey, L.H. Ngo, S.G. Leveille, E.P. McCarthy.

Drafting of the article: C.C. Wee, L.H. Ngo, A. Fowler-Brown.

Critical revision of the article for important intellectual content: L.H. Ngo, S.G. Leveille, M.A. Mittlemen, E.P. McCarthy.

Final approval of the article: L.H. Ngo, A. Fowler-Brown, S.G. Leveille, M.A. Mittlemen, E.P. McCarthy.

Statistical expertise: L.H. Ngo, S.G. Leveille, M.A. Mittlemen.

Obtaining of funding: C.C. Wee.

Administrative, technical, or logistic support: C.C. Wee, E.P. McCarthy.

Collection and assembly of data: E.P. McCarthy.


Ann Intern Med. 2011;154(10):645-655. doi:10.7326/0003-4819-154-10-201105170-00003
Text Size: A A A

Background: The adverse effect of obesity on health outcomes may be lower in older and African American adults than in the general U.S. population.

Objective: To examine and compare the relationship between obesity and all-cause mortality and functional decline among older U.S. adults.

Design: Longitudinal cohort study.

Setting: Secondary analysis of data from the 1994 to 2000 Medicare Current Beneficiary Surveys, linked to Medicare enrollment files through 22 April 2008.

Participants: 20 975 community-dwelling participants in the 1994 to 2000 Medicare Current Beneficiary Surveys who were aged 65 years or older.

Measurements: All-cause mortality through 22 April 2008; new or worsening disability in performing activities of daily living (ADLs) and instrumental activities of daily living (IADLs) in 2 years.

Results: 37% of the study sample were overweight (body mass index [BMI] of 25 to <30 kg/m2), 18% were obese (BMI ≥30 kg/m2), 48% died during the 14-year follow-up, and 27% had ADL and 43% had IADL disability at baseline. Among those without severe disability at baseline, 17% developed new or worsening ADL disability and 26% developed new or worsening IADL disability within 2 years. After adjustment, adults with a BMI of 35 kg/m2 or greater were the only group above the normal BMI range who had a higher risk for mortality (hazard ratio, 1.49 [95% CI, 1.20 to 1.85] in men and 1.21 [CI, 1.06 to 1.39] in women, compared with the reference group [BMI of 22.0 to 24.9 kg/m2]; P for BMI–sex interaction = 0.003). In contrast, both overweight and obesity were associated with new or progressive ADL and IADL disability in a dose-dependent manner, particularly for white men and women. Significant interactions were detected between BMI and sex but not between BMI and race for any outcome, although risk estimates for ADL disability seemed attenuated in African American relative to white respondents.

Limitation: This was an observational study, baseline data were self-reported, and the study had limited power to detect differences between white and African American respondents.

Conclusion: Among older U.S. adults, obesity was not associated with mortality, except for those with at least moderately severe obesity. However, lower levels of obesity were associated with new or worsening disability within 2 years. Efforts to prevent disability in older adults should target those who are overweight or obese.

Primary Funding Source: National Institute of Diabetes and Digestive and Kidney Diseases.

Figures

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Figure 1.
Age- and smoking-adjusted mortality rate (deaths per 100 000 person-years), overall and by sex and race.

Rates are derived through direct standardization with applied survey weights. BMI = body mass index.

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Figure 2.
Relationship between BMI and death or disability.

Adjusted hazard ratios for death (top) and adjusted risk ratios for developing new or progressive ADL (middle) or IADL (bottom) disability. Death was assessed at up to 14 y from the baseline interview. Disability was assessed at 1 and 2 y after the baseline interview. All models were adjusted for baseline age, smoking status, highest education, proxy response, and individual non–obesity-related comorbid conditions (chronic lung disease, rheumatoid arthritis, cognitive impairment, and cancer); a few persons with HIV or AIDS (<15 respondents) were excluded. Models included a BMI–race–sex interaction term, with a BMI of 22.0–24.9 kg/m2 used as the reference category within each race- or sex-specific comparision. ADL = activity of daily living; BMI = body mass index; IADL = instrumental activity of daily living.

* Fewer than 30 African American respondents in the sample were in this BMI category.

† Analyses excluded respondents with any ADL disability at baseline, as well as those in the underweight (<18.5 kg/m2) BMI category (because of zero sample sizes).

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Comments

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Overweight -- Pros and Cons
Posted on June 20, 2011
John H. Glaser
(Unaffiliated)
Conflict of Interest: None Declared

TO THE EDITOR: Wee and colleagues (1) have found that overweight people (body mass index [BMI] 25 to <30) are more likely to have difficulty performing certain activities of daily living (for example, getting out of chairs or walking) and performing certain instrumental activities of daily living (for example, shopping or doing heavy housework). A possible explanation for the correlation of overweight and disability is hypothyroidism. Symptoms of hypothyroidism include a modest weight gain (10 to 20 pounds), fatigue, muscle aches, muscle weakness in the lower extremities, and pain and stiffness in the joints (2). Wee and colleagues also have found that overweight (but not obese) people have a lower mortality rate than people with a BMI 18.5 to 24.9. A possible explanation for this correlation involves the protective effect of fat. In the event of a fall, the additional "padding" reduces the likelihood of a hip fracture, thereby avoiding the risk of surgical complications and the risk of blood clots occurring after extended periods of traction (3).

John H. Glaser (Unaffiliated) Lexington, MA 02421

References

1. Wee CC, Huskey KW, Ngo LH, et al. Obesity, race, and risk for death or functional decline among Medicare beneficiaries. Ann Intern Med. 2011;154:645-655.

2. http://www.mayoclinic.com/health/hashimotos- disease/DS00567/DSECTION=symptoms, June 13, 2011 3. Glaser JH. Survival of the fattest. J Amer Ger Soc. 2010;58(7):1407.

Conflict of Interest:

None declared

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Summary for Patients

Obesity and the Ability to Carry Out Daily Activities

The full report is titled “Obesity, Race, and Risk for Death or Functional Decline Among Medicare Beneficiaries. A Cohort Study.” It is in the 17 May 2011 issue of Annals of Internal Medicine (volume 154, pages 645-655). The authors are C.C. Wee, K.W. Huskey, L.H. Ngo, A. Fowler-Brown, S.G. Leveille, M.A. Mittlemen, and E.P. McCarthy.

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