Context The effect of age on excess mortality from all
causes associated with obesity is controversial. Few studies have
investigated the association between body mass index (BMI, calculated
as weight in kilograms divided by the square of height in meters), age,
and mortality, with sufficient numbers of subjects at all levels of
Objective To assess the effect of age on the excess mortality
associated with all degrees of obesity.
Design Prospective cohort study.
Setting and Participants A total of 6193 obese patients with mean
(SD) BMI of 36.6 (6.1) kg/m2 and mean (SD) age of 40.4
(12.9) years who had been referred to the obesity clinic of
Heinrich-Heine University, Düsseldorf, Germany, between 1961 and
1994. Median follow-up time was 14.8 years.
Main Outcome Measure All-cause mortality through 1994 among 6053
patients for whom follow-up data were available (1028 deaths) analyzed
as standardized mortality ratios (SMRs) using the male-female
population of the geographic region (North Rhine Westphalia) as
Results The cohort was grouped into approximate quartiles
according to age (18-29, 30-39, 40-49, and 50-74 years) and BMI (25 to
<32, 32 to <36, 36 to <40, and ≥40 kg/m2) at
baseline. The SMRs showed a significant excess mortality with an SMR
for men of 1.67 (95% confidence interval, 1.51-1.85;
P<.001) and an SMR for women of 1.45 (95% confidence
interval, 1.34-1.57; P<.001). The excess mortality
associated with obesity declined with age. For men, the SMRs of the 4
age groups were 2.46, 2.30, 1.99, and 1.31, respectively; for women,
they were 1.81, 2.10, 1.70, and 1.26, respectively (Poisson trend test,
P<.001). The SMRs increased with BMI but, within each BMI
group, the SMRs decreased with age. The lowest SMRs (for men, 1.01; for
women, 0.91) were obtained for patients older than 50 years with BMIs
of 25 to less than 32 kg/m2. Thus, older men and women at a
BMI range of 25 to less than 32 kg/m2 had no excess
mortality. The highest SMRs (for men, 4.22; for women, 3.79) were
calculated for the patients aged 18 to 29 years with a BMI of 40
kg/m2 or higher.
Conclusions In this large cohort of obese persons, risk of
death increased with body weight, but obesity-related excess mortality
declined with age at all levels of obesity.