Increased cardiovascular (CV) risk in polycystic ovary syndrome (PCOS) is assumed, based on associated risk factors including insulin resistance. Previous research is conflicting owing to heterogeneity in study design and definitions of both PCOS and CV disease (CVD). This retrospective cohort study examined CV outcomes using a uniformly diagnosed cohort of women with PCOS vs. controls using linked health data.
NIH-defined PCOS patients were identified from endocrinology clinics in Western Australia. Control women were identified from the WA electoral role and matched, 1(case):4(controls), by age, sex, postcode and Indigenous status. Clinical data for the cases were linked with administrative data from the Western Australian (WA) Data Linkage System.
CV outcomes were identified from linked hospital admissions, and included coronary heart disease, heart failure, atrial fibrillation/arrhythmia, cardiac arrest, cerebrovascular disease, and peripheral vascular disease. Events were examined collectively, based on a composite of these outcomes, and as individual outcomes. Multivariable stratified Cox proportional hazards regression models with time-dependent covariates were used to examine the effect of PCOS on CV outcomes.
Overall, 1035 PCOS-affected women and 4148 controls were followed for an average of 33.0 (SD 9.6) years. PCOS cases had higher incidence of diabetes, hypertension, COPD and fatty liver; these covariates were included as time dependent variables in models. Unadjusted hazard ratios showed significantly higher risk of both overall CVD (ICD-9_CM codes 390-459, ICD-10-AM I00-I99) (HR 1.33, CI 1.14-1.56) and the composite CV endpoint (unadjusted HR 1.55, CI 1.07-2.24). However, following adjustment for the time dependent variables the HR for composite CV outcome in cases vs. controls was 1.17 (95% CI 0.81-1.68).
The difference in findings following adjustment for diabetes and hypertension, implies that PCOS per se is not the cause of differences in CV outcome. Instead, this suggests traditional CV risk factors drive CV risk in women with PCOS.