| Abstract: | ALLISON, DAVID B., MYLES S. FAITH, MOONSEONG HEO, DIANA TOWNSEND-BUTTERWORTH, AND DAVID F. WILLIAMSON. Meta-analysis of the effect of excluding early deaths on the estimated relationship between body mass index and mortality. Obes Res. Objectives: Prospective cohort studies typically observe U-or J-shaped relationships between body mass index (BMI) (kg/m2) and mortality. However, some studies suggest that the elevated mortality at lower BMIs is due to confounding by pre-existing occult disease and recommend eliminating subjects who die during the first several (k) years of follow-up. This meta-analysis tests the effects of such early death exclusion on the BMI-mortality association. Research Methods and Procedures: Studies identified from MEDLINE, review articles, ancestry analyses, and the “invisible college.” Included studies: 1) measured relative body weight at baseline; 2) inchded at least 1000 subjects; 3) reported results with and without early-death exclusion, or relevant data; and 4) did not study exclusively diseased populations. Blank tables were mailed to 131 investigators covering 59 databases. Completed tables (n = 16 databases), electronic raw data (n = 7 databases), and original articles (n = 6 databases) provided final data. Meta-analytic regressions compared the BMI-mortality association with and without early death exclusion. The sample included 29 studies and 1,954,345 subjects. Results: The effect of eliminating early deaths was statistically significant but minuscule in magnitude. Implementation of early death exclusion was estimated to shift the BMI associated with minimum mortality only 0. 4 units for men and 0. 6 units for women at age 50. Even at a BMI 16, the estimated relative risk (compared to BMI 25) decreased only 0. 008 units for men and 0. 076 units for women at age 50. Discussion: Results indicate that either pre-existing disease does not confound the BMI—mortality association or eliminating early deaths is inefficient for reducing that confounding. |
