Incidence of Cardiovascular Disease and Mortality in Underweight Individuals

BACKGROUND: Few studies have evaluated the association between being underweight and cardiovascular disease in the general population. We investigated the incidence of stroke, myocardial infarction (MI), and all-cause mortality according to detailed underweight categories in a large population cohort. METHODS: We included 4,164,364 individuals who underwent a health examination provided by the Korean National Health Insurance Service between January 2009 and December 2012 and followed them up to determine the incidence of stroke, MI, and total mortality until December 31, 2016. The study population was categorized according to the body mass index into normal (18·50–22·99), mild (17·00–18·49), moderate (16·00–16·99), and severe underweight categories (<16·00). Cox proportional hazards analyses were performed to calculate the hazard ratio (HR) for stroke, MI, and mortality according to the severity of underweight with reference to the normal weight. We adjusted for age, sex, lifestyle, economic status, comorbidity, blood pressure, glucose, lipid level, and waist circumference. FINDINGS: Overall, 46,728 stroke, 30,074 MI, and 121,080 death occurred during 27,449,902 person-years. The incidence of stroke, MI, and total mortality increased proportionally to the severity of underweight in multivariate model. This proportional association became more evident after further adjusting for the WC. The respective HRs (95% confidence intervals) associated with mild, moderate, and severe underweight were 1·10 (1·06–1·15), 1·11 (1·02–1·20), and 1·38 (1·24–1·53) for stroke; 1·19 (1·14–1·25), 1·40 (1·27–1·53), and 1·86 (1·64–2·11) for MI; and 1·63 (1·60–1·67), 2·10 (2·02–2·17), and 2·98 (2·85–3·11) for total mortality. INTERPRETATION: The severity of underweight was associated with higher risk of stroke, MI, and all-cause mortality. The underlying mechanism might be related to a low lean body mass, rather than a low fat mass. FUNDING STATEMENT: The authors received no financial support for the research, authorship, and/or publication of this article. DECLARATION OF INTERESTS: The authors declare no competing interests. ETHICS APPROVAL STATEMENT: The Seoul National University Hospital (Seoul, South Korea) institutional review board approved this study (IRB no. E-1809-073-973). The requirement for written informed consent was waived by the review board because anonymous and de-identified information was used for analysis.