Associations between being obese but metabolically healthy and risk of myocardial infarction, stroke and mortality - a nationwide study of fertile women

Abstract

Purpose: Obese middle-aged men without metabolic disturbances have recently been found to carry the same cardiovascular risk as their normal weight, metabol-ically healthy counterparts. In this setting we examined the risk of myocardial infarction, ischemic stroke and all-cause mortality in a large population of young fertile women. Methods: From nationwide registers of birth records we identified all Danish women giving birth in the period 2004-2010. Metabolically unhealthy was defined as the presence of either a hypertensive disorder (gestational hypertension, preeclampsia, hypertension), an abnormal glucose metabolism (gestational diabetes, diabetes) or dyslipidemia. Four exposure groups were defined according to metabolic health status and pre-pregnancy body mass index (BMI): Metabolically healthy and a BMI< 25 kg/m2 (1) or a BMI≥ 25 kg/m2 (2), metabolically unhealthy and a BMI< 25 kg/m2 (3) or BMI≥ 25.0 kg/m2 (4), respectively. Using Poisson regression models adjusted for age and calendar year, the risk of the combined end-point of myocardial infarction, ischemic stroke and all-cause mortality was assessed with (1) as reference. Results: The population consisted of 273, 101 women with a mean age of 31.2 (SD 4.9) years and a median follow up of 5.5 years (IQR 3.8; 6.8). In the normal weight metabolically healthy women (1) the incidence rate (IR) per 1000 person years for the combined endpoint was 0.41 (95% confidence interval [CI] 0.37-0.45, number of events, n=375). For the obese but metabolically healthy women (2) the IR was 0.45 (CI 0.39-0.52, number of events, n=51) and rate ratio (RR) was 1.16 (CI 0.93-1.33). In the normal weight but metabolically unhealthy women (3) the IR was 0.91 (CI 0.69-1.2, number of events, n=175) and RR was 2.11 (CI 1.58-2.83). The IR for the obese and metabolically unhealthy women (4) was 1.25 (CI 1.01-1.54, number of events, n=86) and the RR was 2.81 (CI 2.22-3.56). Conclusions: In a nationwide low risk population of young fertile women being obese but metabolically healthy confers a similar risk of myocardial infarction, stroke and all-cause mortality compared to normal weight, metabolically healthy women, while metabolically unhealthy women had increased risk of MI, stroke and all-cause mortality irrespective of BMI.