Researchers have looked at the possible role of number and order of siblings on an individual’s risk of cardiovascular disease.
Previous work has suggested no link between number of siblings and total or cause-specific mortality, but non-fatal cardiovascular disease and coronary disease were not examined specifically. In terms of birth order, there is small evidence of higher cardiovascular risk factors in first borns.
Now, Professor Peter Nilsson of Lund University in Sweden, and colleagues, searched for associations using a multiple generation register including 1.36 million men and 1.32 million women followed for around 25 years.
This showed that first-born men and women have a lower risk of non-fatal cardiovascular and coronary events than siblings born later.
Compared with men with no siblings, those with one or two siblings had a lower risk of cardiovascular events, and those with four or more siblings had a higher risk. The pattern was similar for women, and for overall mortality risk among men and women.
Details appear today (26 May) in BMJ Open. The authors write: "Being first born is associated with a favourable effect on non-fatal cardiovascular and coronary events for both men and women."
They call for the underlying biological mechanisms for this to be studied further, as this was an observational study and cannot establish cause and effect. They add that lifestyle factors, such as body mass index, smoking and diet, were not available and could not be taken into account.
Nilsson, P. M. et al. Sibling rank and sibling number in relation to cardiovascular disease and mortality risk: a nationwide cohort study. BMJ Open 26 May 2021 doi: 10.1136/bmjopen-2020-042881
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