Birth Order, Family Size May Affect Heart Health

It's known that genetics and lifestyle can affect your heart health. Now, researchers say, your birth order and family size may also have an impact.

A new Swedish study found that first-born children had a lower risk of heart attacks and strokes than their younger brothers and sisters. But having many siblings was associated with an increased risk of such cardiovascular events.

"More research is needed to understand the links between sibling number and rank with health outcomes," said the researchers, led by Peter Nilsson, from Lund University in Malmö. "Future research should be directed to find biological or social mechanisms linking the status of being first-born to lower risk of cardiovascular disease."

For the study, the authors accessed data on more than 2.6 million adults born between 1932 and 1960. The study participants were between the ages of 30 and 58 in 1990.

The researchers also gathered data from national registers on fatal and nonfatal heart problems and strokes that happened over the next 25 years.

Overall, the investigators found that first-borns had a lower risk of nonfatal cardiovascular and coronary events than siblings born later.

But first-born men had a higher risk of death than second- and third-born siblings, while first-born women had a higher risk of death than second-born siblings, but equal to further siblings.

What about "only" children?

Compared with men with no siblings, men with one or two siblings had a lower risk of heart attack and stroke, while those with four or more siblings had a higher risk. Also, compared with men who had no siblings, men with more than one sibling had a lower risk of death, while those with three or more siblings had an increased risk of coronary events.

That pattern was reflected in women as well, according to the report published online May 25 in the BMJ Open.

Policies to support families and the number of children currently vary widely between countries, and these findings could have implications for public health, the authors said in a journal news release.

The researchers considered relevant factors such as income, obesity, diabetes and alcoholism, but did not have information on diagnostic procedures or lifestyle behaviors like smoking and diet, which is a study limitation.

Because this was an observational study, it can show an association, but not cause and effect, the study authors added.