Women’s CVD mortality risk may depend on their birth season
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Women born in during spring and summer — particularly those born from March to July — have an increased risk for CVD-related mortality, according to a study published in BMJ.
“Mechanisms driving the seasonal birth month effect in mortality may involve both prenatal and early postnatal exposures,” Eva S. Schernhammer, MD, DrPH, an associate professor of medicine at Harvard Medical School, told Healio Primary Care. “Prior studies suggested that these may include seasonal fluctuations in nutrition availability, infections and inflammatory causes, climatic temperature and air pollution, or sunlight exposure (maternal vitamin D levels and solar cycles) as well as near-birth familial/socioeconomic factors.”
Schernhammer and colleagues evaluated data from women who participated in the Nurses’ Health Study, on ongoing study of women in the United States that began in 1976.
Using November and autumn as reference groups, researchers evaluated the risk for cardiovascular and overall mortality by birth month and season.
Researchers found that among the 116,911 women enrolled in the study, a total of 43,248 died by 2014 — and 8,360 of these deaths were attributed to CVD.
They did not find a significant association between birth month or season and overall mortality risk. However, compared with those born in November, CVD-related mortality risk was higher among those born in March (HR = 1.09; 95% CI, 0.98-1.21), April (HR = 1.12; 95% CI, 1-1.24), May (HR = 1.08; 95% CI, 0.98-1.2), June (HR = 1.07; 95% CI, 0.96-1.19) and July (HR = 1.08; 95% CI, 0.98-1.2). Those born in December had the lowest risk for cardiovascular disease (HR = 0.95; 95% CI, 0.85-1.06), researchers said.
When looking at birth season, researchers found elevated CVD mortality risk among those born in the spring (HR = 1.1; 95% CI, 1.04-1.17) and summer (HR = 1.09; 95% CI, 1.03-1.16).
The risks did not change significantly after adjusting for familial and socioeconomic characteristics, according to the researchers.
Schernhammer explained that the study supports associations between fetal and early life factors with CVD, and “may relate to a small but real seasonal fetal/early months of life effect on later life.”
“Further investigations are required to confirm the current findings and uncover mechanisms of seasonal birth month effect in CVD mortality,” she explained. – by Erin Michael
Disclosures: Schernhammer reports no relevant financial disclosures. Please see the study for all other authors’ relevant financial disclosures.