Risk of hospitalization for early onset of cardiovascular disease among infertile women: a register-based cohort study

Abstract STUDY QUESTION Is female infertility predictive of a woman’s future risk of early cardiovascular disease (CVD)? SUMMARY ANSWER Female infertility does not seem to be predictive of early CVD during a mean follow-up of 9 years. WHAT IS KNOWN ALREADY Associations between infertility and comorbidity have been found in several studies, but data on the association between female infertility and risk of CVD are scarce and inconclusive. STUDY DESIGN, SIZE, DURATION In this nationwide cohort study, we included 87 221 women registered in the Danish National IVF register, undergoing medically assisted reproduction (MAR) between 1st of January 1994 and 31st of December 2015. The cohort was followed for incident hospitalization due to CVD in the Danish National Patient Register from enrollment to 31 December 2015. Women with a history of CVD prior to enrollment were excluded. Cox proportional hazard models with age as the underlying time scale were used to estimate hazard ratios (HR) with 95% CI of CVD among women with an infertility diagnosis, compared to women without an infertility diagnosis. All analyses were adjusted for educational attainment. PARTICIPANTS/MATERIALS, SETTING, METHODS Female infertility and the reason for infertility was diagnosed and registered in the IVF register by specialists in Danish public and private fertility clinics since 1st of January 1994. In our cohort, 53 806 women (61.7%) were diagnosed with female factor infertility, while 33 415 (38.3%) did not have a female factor infertility diagnosis and made up the reference group. MAIN RESULTS AND THE ROLE OF CHANCE A total of 686 (1.3%) infertile women were hospitalized for CVD compared to 250 (0.7%) among women without an infertility diagnosis during a mean follow-up time of 9 years. We found no increased risk of early CVD in our analyses (adjusted HR 0.98, 95% CI: 0.85;1.14). Likewise, analyses stratified by specific infertility diagnosis, showed no risk difference. LIMITATIONS, REASONS FOR CAUTION We were unable to adjust for confounding parameters such as body mass index, cigarette smoking or alcohol consumption. These results may not be generalizable to infertile women who do not seek out fertility treatment, or infertile women with other lifestyle characteristics than Danish women. WIDER IMPLICATIONS OF THE FINDINGS Diagnosing female infertility or the time of MAR does not seem to be a window of opportunity where early screening for cardiovascular disease risk factors can hav