Metabolic health strongly influences body mass index (BMI) impact on mortality

Obesity and mortality in middle and late life
In midlife, a higher body mass index (BMI) and unfavorable metabolic health, which often coexist as metabolic syndrome (MetS), are related to increased mortality risk. However, late-life findings are inconsistent, and it is unclear how metabolic health status (MHS) influences the relationship between BMI and mortality across different age groups. This study examined whether mid and late-life BMI and MHS affect mortality risk.

Photo: Matt Love, Maura Murphy. Photographer Website: www.icpobesity.org

Three NEAR population studies: The Swedish Adoption/Twin Study of Aging (SATSA), Ageing in Women and Men: A Longitudinal Study of Gender Differences in Health Behavior and Health among Elderly (GENDER), and Origin of Variances in the Oldest-Old: Octogenarian Twins (OCTO-Twin), as well as the TwinGene were used to explore this. A total of 6252 individuals aged 45-65 years in midlife, and 6215 individuals aged 65.1-95 years in late life were included in the study.

Metabolic health strongly influences body mass index (BMI) impact on mortality
While obesity, in mid and late life, was independently associated with a 30% and 15% higher mortality risk, their associations weakened when considering individuals’ metabolic health status. When examining the combined effect of BMI and MHS on mortality, individuals with unhealthy MHS and obesity in midlife had a 53% higher risk of mortality, compared to those who were metabolically healthy and normal weight (MHN). In late life, the risk was elevated for everyone with unhealthy MHS, across all BMI classifications. In fact, being metabolically healthy and overweight was associated with lower mortality risk, compared to MHN. It may be appropriate to consider both BMI and MHS when evaluating individuals’ health status and mortality risk.

Peggy Ler, first author of the study. Photo: Gunilla Sonnebring

Publication
Ler P, Li X, Hassing LB, Reynolds CA, Finkel D, Karlsson IK, Dahl Aslan AK. Independent and joint effects of body mass index and metabolic health in mid- and late-life on all-cause mortality: a cohort study from the Swedish Twin Registry with a mean follow-up of 13 Years. BMC Public Health. 2022; 22(1): 718. https://doi.org/10.1186/s12889-022-13082-3.