Optimum body mass index for elderly

[Guest guest]

Hi All,

This is not such a new study, but I found it to be of particular importance

for my decision about whether to reduce weight when I get older. The risk

seems to keep getting better with lower weights, even among the elderly,

when careful analysis is done.

Cheers, Al.

Int J Obes Relat Metab Disord 2001 Jul;25(7):1071-8

Biases in the mortality risk versus body mass index relationship in the

NHANES-1 Epidemiologic Follow-Up Study.

Greenberg JA

PMID: 11443509 [PubMed - indexed for MEDLINE]

“Among non-elderly persons, being leaner meant a lower mortality risk, down

to the lowest category of leanness in the study-<20 kg/m(2)”

Alan Pater, Ph.D.; Faculty of Medicine; Memorial University; St. 's, NF

A1B 3V6 Canada; Tel. No.: (709) 777-6488; Fax No.: (709) 777-7010; email:

apater@...

1: Int J Obes Relat Metab Disord 2001 Jul;25(7):1071-8

Biases in the mortality risk versus body mass index relationship in the NHANES-1

Epidemiologic Follow-Up Study.

Greenberg JA.

Department of Health and Nutrition Sciences, Brooklyn College, New York 11210,

USA. jamesg@...

BACKGROUND: Conflicting research findings have created uncertainty as to the

ideal body weight. OBJECTIVE: To test whether average-adulthood BMI (body mass

index, weight in kilograms per height in meters squared) is a more reliable

predictor of mortality risk than the one-time baseline BMI measurement which has

been used in previous studies. DESIGN: Prospective cohort study with a 20 y

follow-up period, the First National Health and Examination Survey (NHANES 1)

Epidemiologic Follow-up Study (NHEFS). SUBJECTS: A random probability sample of

14,407 adults aged 25-74 y in the 1971-1975 NHANES 1. MEASUREMENTS: Body-weight

data were derived from measurements in the 1971-1975 and 1982-1984 NHEFS

surveys, and current and recalled estimates by subjects in the 1971-1975,

1982-1984, 1986 and 1987 surveys. Height was measured in the 1971-1975 survey.

Socio-economic and lifestyle covariates were derived from questionnaires

administered in all four surveys. Almost all deaths were verified by death

certificates. RESULTS: The shape of the morality risk vs baseline BMI curve

varied due to a bias (late-life bias) caused by a steep decrease in BMI among

the elderly toward the end of the lifespan. In a particular analysis, the

portion of subjects at baseline who were deceased elderly with lower BMI than

age-matched censored subjects indicated the size of the bias, and appeared to be

the proximate cause. Strong evidence was found to support the proximate cause

being the actual cause. Excluding deaths during early follow-up was only able to

remove the late-life bias in limited circumstances. Using average-adulthood BMI

as mortality predictor and baseline BMI as covariate was very effective in

removing the late-life bias. It also appeared to remove the reverse-causation

and regression-dilution biases, and yielded robustly positive mortality risk vs

average-adulthood BMI curves in all analyses in which it was tested.

CONCLUSIONS: Average-adulthood BMI appears to be an appropriate predictor of

mortality risk, provided baseline BMI is used as a covariate. Among non-elderly

persons, being leaner meant a lower mortality risk, down to the lowest category

of leanness in the study-<20 kg/m(2). Future survival analyses of the

mortality-BMI relationship should account for the effects of the

regression-dilution, reverse-causation and late-life biases.

PMID: 11443509 [PubMed - indexed for MEDLINE]