How many siblings you have, being first-born impacts heart disease risk

MALMÖ, Sweden — Are you the first born in your family? If so, a new study finds you’re at a lower risk of suffering a heart attack than your brothers and sisters. Moreover, Swedish researchers report the more siblings one has in general, the more likely they are to experience adverse cardiovascular events.

Usually, when heart issues occur, doctors look to mom, dad, grandma, and grandpa for any signs of heart disease in the family. This new work suggests it may be time to start considering order of birth and number of immediate siblings as well.

This was no small study; researchers analyzed data pertaining to 1.36 million men and 1.32 million women between 30 and 58 years-old in 1990. All that information is part of the Multiple-Generation Register in Sweden. For 25 years (up until 2015), the study tracked all of those individuals’ fatal and non-fatal cardiovascular and coronary events.

A comprehensive analysis of all that data revealed first-born children generally had a lower risk of non-fatal cardiovascular and coronary events than their younger siblings.

Regarding risk of death, the results show some gender differences among first-born children. First-born males had a higher risk of death than second and third-born siblings, while first-born females only had a higher risk of death in comparison to second-born siblings.

Why number of siblings affects heart health not yet known

Moving on to family size, men with one or two siblings actually had the lowest risk of a cardiovascular event, followed by men with no siblings. Meanwhile, those with four or more siblings had the highest risk. The team discovered similar findings regarding the risk of death.

For females, women with three or more siblings had an increased risk of cardiovascular events in comparison to women with no siblings. Women with two or more siblings had an increased risk of coronary events, and females with one or more siblings had a lower risk of death.

Ultimately, this research is observational in nature, and thus cannot establish a cause for these trends. However, study authors also examined a number of factors including socioeconomic status, obesity, diabetes, chronic lung disease (COPD), and alcoholism while compiling the results.

“More research is needed to understand the links between sibling number and rank with health outcomes,” study authors conclude in a media release. “Future research should be directed to find biological or social mechanisms linking the status of being first born to lower risk of cardiovascular disease, as indicated by our observational findings.”

The study appears in the journal BMJ Open.