Weight change across adulthood ups risks of mortality

Stable obesity across adulthood, weight gain from young to middle adulthood and weight loss from middle to late adulthood appear to increase the risks of all-cause and cardiovascular mortality, according to a recent study.

“The findings imply that maintaining normal weight across adulthood, especially preventing weight gain in early adulthood, is important for preventing premature deaths in later life,” the researchers said.

This prospective cohort study included 36,051 individuals aged ≥40 years with measured body weight and height at baseline and recalled weight at young adulthood (25 years old) and middle adulthood (10 years before baseline). Outcome measures included all-cause and cause-specific mortality from baseline until 31 December 2015.

A total of 10,500 deaths occurred during a mean follow-up of 12.3 years. Participants who moved from nonobese to obese status from young to middle adulthood had a 22-percent (hazard ratio [HR], 1.22, 95 percent CI, 1.11–1.33) and 49-percent (HR, 1.49, 1.21–1.83) higher risk of all-cause and cardiovascular mortality, respectively, than those who maintained a normal weight. A change from obese to nonobese category over this period did not significantly correlate with mortality risk. [BMJ 2019;367:l5584]

Changing from obese to nonobese from middle to late adulthood correlated with a higher risk of all-cause (HR, 1.30, 1.16–1.45) and cardiovascular mortality (HR, 1.48, 1.14–1.92), but moving from nonobese to obese status over this period did not significantly correlate with mortality risk.

Stable obesity status across adulthood showed a consistent association with an increased risk of all-cause mortality (young to middle adulthood: HR, 1.72, 1.52–1.95; young to late adulthood: HR, 1.61, 1.41–1.84; middle to late adulthood: HR, 1.20, 1.09–1.32). The association between maximum overweight and mortality across adulthood was very modest or null.

There were no significant associations between weight change patterns and cancer mortality.

“The association between body mass index (BMI) and mortality has been extensively studied in many prospective cohort studies,” according to the researchers. “However, most studies were conducted in middle aged or older participants and in general a U-shaped association was reported.” [Lancet 2016;388:776-786]

A similar conclusion was reached in the current study, using the baseline BMI as the exposure when the mean age of the participants was 57 years old. However, this and other studies demonstrated that BMI in early adulthood had a linear association with an increased risk of mortality in later life. [Am J Epidemiol 2015;182:441-450; Am J Epidemiol 2011;174:934-944; J Adolesc Health 2012;50:221-227]

Additionally, about 80 percent of the current participants who were obese in young adulthood remained obese in middle or late adulthood. These results were consistent with those of earlier studies reporting an association between longer obesity duration and higher mortality risk. [Epidemiology 2013;24:158-166; Int J Epidemiol 2011;40:985-996]

“Future studies are needed to unravel the mechanisms underlying the association between weight change across adulthood and mortality, particularly the relations of changes in body composition to mortality,” the researchers said. “In addition, as weight loss is less achievable, our results suggest that prevention of weight gain might be more important.”