Survival in older men may benefit from being slightly overweight and centrally obese--a 5-year follow-up study in 4,000 older adults using DXA.
BACKGROUND
Whether overweight in old age is hazardous remains controversial. Body mass index (BMI) overestimates adiposity and fails to measure central adiposity. We used dual-energy x-ray absorptiometry (DXA) to measure adiposity and hypothesized that overall adiposity, distribution of adiposity, and muscle mass might individually affect survival.


METHODS
We recruited 2000 men and 2000 women aged 65 years or older. Baseline BMI, waist-hip ratio (WHR), body fat index (BFI = total body fat/height square), relative truncal fat (RTF = trunk fat/total body fat), and body muscle mass index (BMMI = total body muscle mass/height square) were measured. Mortality was ascertained by death registry after 63.3 (median) months.


RESULTS
Two hundred and forty-two men and 78 women died. In men, mortality hazard ratio (HR) decreased consistently by 0.85 (p < .005), 0.86 (p < .005), and 0.86 (p < .005) per every quintile increase in BMI, BFI, and BMMI, respectively. A J-shaped relationship was observed in central adiposity (RTF and WHR) quintiles; the minimum values were at the 3rd WHR quintile (0.92-0.94) and 4th RTF quintile (mean WHR, 0.94). When RTF was tested with BFI, both high and low central adiposity were unfavorable while general adiposity became marginally insignificant (p = 0.062). When BFI and BMMI were tested together, increasing adiposity rather than muscle mass favored survival (BFI quintile, HR 0.97, p .015; BMMI quintile, HR 1.00, p .997).


CONCLUSIONS
Older men were resistive to hazards of overweight and adiposity; and mild-grade overweight, obesity, and even central obesity might be protective. This may bear significant implication on the recommended cutoff values for BMI and WHR in the older population.
Auyeung
Tung Wai
TW
Department of Medicine and Geriatrics, Tuen Mun Hospital, Tuen Mun, Hong Kong, China. auyeungtw@cuhk.edu.hk
Lee
Jenny S W
JS
Leung
Jason
J
Kwok
Timothy
T
Leung
Ping Chung
PC
Woo
Jean
J
D015502:Absorptiometry, Photon / Q000379:methods*; D000368:Aged; D050218:Body Fat Distribution; D015992:Body Mass Index; D001835:Body Weight / Q000502:physiology*; D005260:Female; D005500:Follow-Up Studies; D006723:Hong Kong / Q000453:epidemiology; D006801:Humans; D008297:Male; D009765:Obesity / Q000175:diagnosis / Q000401:mortality* / Q000503:physiopathology; D050177:Overweight / Q000175:diagnosis / Q000401:mortality* / Q000503:physiopathology; D011379:Prognosis; D012189:Retrospective Studies; D012307:Risk Factors; D012720:Severity of Illness Index; D012737:Sex Factors; D015996:Survival Rate / Q000639:trends; D013997:Time Factors