Higher Body Mass Index in Adolescence Predicts Cardiomyopathy Risk in Midlife

Abstract

Background: Modifiable lifestyle factors in relation to risk for cardiomyopathy, a common and increasing cause of heart failure in the young, have not been widely studied. We sought to investigate a potential link between obesity, a recognized predictor of early heart failure, in adolescence and being diagnosed with cardiomyopathy in adulthood.

Methods: This was a nationwide register-based prospective cohort study of 1 668 893 adolescent men (mean age, 18.3 years; SD, 0.7 years) who enlisted for compulsory military service from 1969 to 2005. At baseline, body mass index (BMI), blood pressure, and medical disorders were registered, along with test results for fitness and muscle strength. Cardiomyopathy diagnoses were identified from the National Hospital Register and Cause of Death Register during an up to 46-year follow-up and divided into categories: dilated, hypertrophic, alcohol/drug-induced, and other. Hazard ratios were calculated with Cox proportional hazards models.

Results: During follow-up (median, 27 years; Q1-Q3, 19-35 years), 4477 cases of cardiomyopathy were identified, of which 2631 (59%) were dilated, 673 (15%) were hypertrophic, and 480 (11%) were alcohol/drug-induced. Increasing BMI was strongly associated with elevated risk of cardiomyopathy, especially dilated, starting at levels considered normal (BMI, 22.5-<25 kg/m²; hazard ratio, 1.38 [95% CI, 1.22-1.57]), adjusted for age, year, center, and baseline comorbidities, and with a >8-fold increased risk at BMI ≥35 kg/m² compared with BMI of 18.5 to <20 kg/m². For each 1-unit increase in BMI, similarly adjusted hazard ratios were 1.15 (95% CI, 1.14-1.17) for dilated cardiomyopathy, 1.09 (95% CI, 1.06-1.12) for hypertrophic cardiomyopathy, and 1.10 (1.06-1.13) for alcohol/drug-induced cardiomyopathy.

Conclusions: Even mildly elevated body weight in late adolescence may contribute to being diagnosed with cardiomyopathy in adulthood. The already marked importance of weight control in youth is further strengthened by these findings, as well as greater evidence for obesity as a potential important cause of adverse cardiac remodeling that is independent of clinically evident ischemic heart disease.

Keywords: adolescent; cardiomyopathies; obesity; overweight; population groups.

Figure.

Association between body mass index (BMI) at conscription and risk for cardiomyopathy (CM). The model was adjusted for age, conscription year (as a spline with knots at 5%, 35%, 65%, and 95%, ie, 1971, 1982, 1992, and 2004), test center, and baseline comorbidities (diabetes mellitus, hypertension, congenital heart disease), systolic blood pressure, diastolic blood pressure, cardiorespiratory fitness, muscle strength, parental education, and alcohol or substance use disorder (n=773 679). BMI was restricted to BMI between 15 and 40 kg/m² and modeled as a restricted cubic spline with knots at 5%, 35%, 65%, and 95% (ie, 18.0, 20.5, 22.4, and 27.5 kg/m²), with BMI of 20 kg/m² as reference. The unadjusted model is presented in Figure II in the online-only Data Supplement.