According to a large American study, our month of birth would influence our risk of dying from heart disease. People whose birthdays fall in the spring and summer would be the first to be affected.
What if the time of year we come into the world could influence our future health?
This question has already motivated many researchers, with varying degrees of success. Previous studies conducted in the northern hemisphere have thus consistently established a link between birth in spring or summer and a higher risk of death, with an opposite trend south of the equator. However, the exact way in which the month of birth influences our future health was until now unclear. A new American study, published in the Christmas issue of British Medical Journalmay have found an explanation.
According to its authors, people born in spring and summer are more affected by heart disease than those born in autumn. This could be linked to seasonal fluctuations in diet, but also to air pollution levels and exposure to sunlight before birth and early in life.
A significant risk of cardiovascular mortality
To reach this conclusion, the researchers used data from 116,911 American nurses recruited as part of the Nurses’ Health Study in 1976. The objective was to examine the links between the month of birth of patients and mortality overall, as well as deaths from cardiovascular disease.
The participants, who were between the ages of 30 and 55 at the start of the study, completed a detailed questionnaire about their health and lifestyle every two years. Death certificates and medical records were then used to determine causes of death over a 38-year follow-up period from 1976 to 2014. A total of 43,000 participants died during the study period of which 8,360 are due to cardiovascular diseases.
By also taking into account other family, economic and social factors, the researchers were able to observe that women born in spring and summer had a slight but nevertheless significant increase in cardiovascular mortality compared to those born during the winter and autumn.
While the authors acknowledge that this is an observational study, they say the results they obtained “add to the growing body of evidence that suggests that people born in spring and summer summer have a higher cardiovascular mortality rate than those born in the fall.”
“Further studies are needed to confirm the current findings and uncover the mechanisms of the seasonal effect of month of birth on cardiovascular mortality,” they conclude.
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