Abstract
Abstract
Background
There is robust evidence that in midlife, higher body mass index (BMI) and metabolic syndrome (MetS), which often co-exist, are associated with increased mortality risk. However, late-life findings are inconclusive, and few studies have examined how metabolic health status (MHS) affects the BMI–mortality association in different age categories. We, therefore, aimed to investigate how mid- and late-life BMI and MHS interact to affect the risk of mortality.
Methods
This cohort study included 12,467 participants from the Swedish Twin Registry, with height, weight, and MHS measures from 1958—2008 and mortality data linked through 2020. We applied Cox proportional hazard regression with age as a timescale to examine how BMI categories (normal weight, overweight, obesity) and MHS (identification of MetS determined by presence/absence of hypertension, hyperglycemia, low HDL, hypertriglyceridemia), independently and in interaction, are associated with the risk of all-cause mortality. Models were adjusted for sex, education, smoking, and cardiovascular disease.
Results
The midlife group included 6,252 participants with a mean age of 59.6 years (range = 44.9—65.0) and 44.1% women. The late-life group included 6,215 participants with mean age 73.1 years (65.1—95.3) and 46.6% women. In independent effect models, metabolically unhealthy status in midlife increased mortality risks by 31% [hazard ratio 1.31; 95% confidence interval 1.12–1.53] and in late-life, by 18% (1.18;1.10–1.26) relative to metabolically healthy individuals. Midlife obesity increased the mortality risks by 30% (1.30;1.06–1.60) and late-life obesity by 15% (1.15; 1.04–1.27) relative to normal weight. In joint models, the BMI estimates were attenuated while those of MHS were less affected. Models including BMI-MHS categories revealed that, compared to metabolically healthy normal weight, the metabolically unhealthy obesity group had increased mortality risks by 53% (1.53;1.19—1.96) in midlife, and across all BMI categories in late-life (normal weight 1.12; 1.01–1.25, overweight 1.10;1.01–1.21, obesity 1.31;1.15–1.49). Mortality risk was decreased by 9% (0.91; 0.83–0.99) among those with metabolically healthy overweight in late-life.
Conclusions
MHS strongly influenced the BMI-mortality association, such that individuals who were metabolically healthy with overweight or obesity in mid- or late-life did not carry excess risks of mortality. Being metabolically unhealthy had a higher risk of mortality independent of their BMI.
Funder
Vetenskapsrådet
Forskningsrådet om Hälsa, Arbetsliv och Välfärd
Foundation for the National Institutes of Health
Strategic Research Program in Epidemiology (SfoEpi), Karolinska Institutet
Jönköping University
Publisher
Springer Science and Business Media LLC
Subject
Public Health, Environmental and Occupational Health
Cited by
1 articles.
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