Improving risk estimates for metabolically healthy obesity and mortality using a refined healthy reference group
journal contributionposted on 08.06.2017, 12:22 by Mark Hamer, Will JohnsonWill Johnson, Joshua A. Bell
Objective: We aimed to re-examine mortality risk estimates for metabolically healthy obesity by using a ‘stable’ healthy non-obese referent group. Design: prospective cohort study. Methods: Participants were 5,427 men and women (aged 65.9 ± 9.4 years, 45.9% men) from the English Longitudinal Study of Ageing. Obesity was defined as body mass index ≥ 30 kg/m2 (vs. non-obese as below this threshold). Based on blood pressure, HDL-cholesterol, triglycerides, glycated haemoglobin, and C-reactive protein, participants were classified as ‘healthy’ (0 or 1 metabolic abnormality) or ‘unhealthy’ (≥ 2 metabolic abnormalities). Results: 671 deaths were observed over an average follow up of 8 years. When defining the referent group based on 1 clinical assessment, the unhealthy non-obese (Hazard ratio = 1.22; 95% CI, 1.01, 1.45) and unhealthy obese (1.29; 1.05, 1.60) were at greater risk of all-cause mortality compared to the healthy non-obese, yet no excess risk was seen in the healthy obese (1.14; 0.83, 1.52). When we re-defined the referent group based on 2 clinical assessments, effect estimates were accentuated and healthy obesity was at increased risk of mortality (2.67; 1.64, 4.34). Conclusion: An unstable healthy referent group may make ‘healthy obesity’ appear less harmful by obscuring the benefits of remaining never obese without metabolic dysfunction.
Hamer acknowledges support from the National Institute for Health Research (NIHR) Leicester Biomedical Research Centre, which is a partnership between University Hospitals of Leicester NHS Trust, Loughborough University and the University of Leicester. Bell is supported by CRUK (C18281/A19169).
- Sport, Exercise and Health Sciences