Ying Gue, PhD
Vyas et al. followed a cohort of 9.2 million adults in Ontario, Canada, over a median period of 15 years in order to identify the incidence of stroke or transient ischemic attack (TIA), identified through health records of hospitalization and emergency department visits. The authors identified an interesting relationship between age, gender and stroke incidence whereby young women were at a much higher risk of stroke when compared to men (HR 1.26, 95% CI 1.10 – 1.45). This risk reverses (men higher risk than women) as age increases (HR 0.69 at age 50 – 59) and equalizes at ages above 80 years. This was mostly true within the ischemic subtypes (ischemic stroke or TIA) but reverses with subarachnoid hemorrhage, with middle-aged women at higher risk than men (HR 1.38, 95% CI 1.29 – 1.48).
The authors postulated that the differences could be due to the changing risk in women across their lifespan, with younger women more likely to be on oral contraceptive pills (OCP) and postmenopausal women losing the protective effect from endogenous oestrogen, therefore being more at risk of thrombotic events. This could also reflect that younger men are less likely to seek medical attention for presumed “mild” symptoms and could partly explain the much higher HR (2.02) within TIA.
Unfortunately, the etiology of stroke was not available, as this could provide further insights into the reason behind the trend identified. Further outcome data, such as mortality, were also not available, which could be an interesting area to explore in identifying if gender differences in risk translate to differences in mortality outcomes.
This study is limited by the potential of unknown confounders, which makes it difficult to draw conclusions, but the authors should be congratulated on using contemporary data which highlights gender differences in risk of cerebrovascular disease. Even within its limitations, the higher risk of strokes in young women is worrying, and whether this could be related to OCP warrants further exploration — to identify at-risk patients and provide appropriate counselling prior to initiation.