Risk of type 2 diabetes according to the cumulative exposure to metabolic syndrome or obesity: A nationwide population‐based study

AIMS/INTRODUCTION: We investigated the risk of incident type 2 diabetes according to the cumulative exposure to obesity or metabolic syndrome (MetS) during annual or biennial health examinations. MATERIALS AND METHODS: The Korean National Health Insurance Service datasets from 2002 to 2017 were used for this retrospective longitudinal study. The risk for type 2 diabetes was analyzed according to the cumulative exposure to obesity and MetS among individuals who underwent four health examinations from 2009 to 2012 or 2013 (n = 2,851,745). RESULTS: During examinations, 28.56 and 17.86% of the total participants showed fluctuations in metabolic health state and obesity, respectively. During a mean 5.01 years of follow up, 98,950 new type 2 diabetes cases developed. The risk for type 2 diabetes increased with the increase in exposure to MetS (hazard ratio [HR] 2.92, 95% confidence interval [CI] 2.86–2.99; HR 4.96, 95% CI 4.85–5.08; HR 7.46, 95% CI 7.30–7.63; HR 12.24, 95% CI 12.00–12.49 in groups with number of exposures one to four, respectively) and obesity (HR 1.60, 95% CI 1.56–1.65; HR 1.87, 95% CI 1.81–1.92; HR 2.25, 95% CI 2.19–2.31; HR 3.46, 95% CI 3.41–3.51 in groups with number of exposures one to four, respectively), showing a more detrimental effect of cumulative exposure to MetS, when compared with the exposure to obesity. CONCLUSIONS: Metabolic health and obesity fluctuated within a relatively short period of 4–5 years. Although the impact was much greater for MetS than for obesity, the cumulative duration of both obesity and MetS was associated with an increased risk of type 2 diabetes in a dose‐response manner. Therefore, continuously maintaining metabolic health and normal weight is crucial to prevent incident type 2 diabetes.