Body Mass Index in Young Women and Risk of Cardiomyopathy: A Long-Term Follow-Up Study in Sweden

Abstract

Background: Incidence rates of cardiomyopathies, which are a common cause of heart failure in young people, have increased during the last decades. An association between body weight in adolescence and future cardiomyopathy among men was recently identified. Whether or not this holds true also for women is unknown. The aim was therefore to determine whether for young women being overweight or obese is associated with a higher risk of developing cardiomyopathy.

Methods: This was a registry-based national prospective cohort study with data collected from the Swedish Medical Birth Register, 1982 to 2014, with up to 33 years of follow-up. Included women were of childbearing age (18-45 years) during the initial antenatal visit in their first or second pregnancy (n=1 393 346). We obtained baseline data on body mass index (BMI), smoking, education, and previous disorders. After exclusions, mainly because of previous disorders, the final sample was composed of 1 388 571 women. Cardiomyopathy cases were identified by linking the Medical Birth Register to the National Patient and Cause of Death registers.

Results: In total, we identified 1699 cases of cardiomyopathy (mean age at diagnosis, 46.2 [SD 9.1] years) during the follow-up with an incidence rate of 5.9 per 100 000 observation years. Of these, 481 were diagnosed with dilated cardiomyopathy, 246 had hypertrophic cardiomyopathy, 61 had alcohol/drug-induced cardiomyopathy, and 509 had other forms. The lowest risk for being diagnosed with a cardiomyopathy was detected at a BMI of 21 kg/m², with a gradual increase in risk with higher BMI, particularly for dilated cardiomyopathy, where a hazard ratio of 4.71 (95% CI, 2.81-7.89) was found for severely obese subjects (BMI ≥35 kg/m²), as compared with BMI 20 to <22.5.

Conclusions: Elevated BMI among young women was associated with an increased risk of being diagnosed with a subsequent cardiomyopathy, especially dilated cardiomyopathy, starting already at mildly elevated body weight, whereas severe obesity entailed an almost 5-fold increase in risk. With the increasing numbers of persons who are overweight or obese, higher rates of cardiomyopathy can be expected in the future, along with an altered disease burden related to adiposity.

Keywords: body mass index; cardiomyopathy; obesity; overweight; population; women.

Figure.

Association between body mass index (BMI) in young women and risk for subsequent cardiomyopathy. The model is adjusted for age, year, parity, comorbidities at baseline, smoking, and level of education (n=1 339 527). BMI is restricted to the range of 15 to 40, and modeled as a restricted cubic spline with knots at 5%, 35%, 65%, and 95% (i.e., 18.9, 21.7, 24.2, and 31.6, respectively), with a BMI of 21 as reference.