If You Have This Many Siblings, Your Heart May Be in Danger, New Study Says

Your family makeup may elevate your risk of a heart dieseae, according to a new report.

Anyone with siblings knows that it can sometimes be a complicated relationship. A shared upbringing can bring you closer together, but it can also be a source of friction. And now, there is also evidence suggesting that your siblings may also affect your heart health—and we're not talking figuratively, either. According to a new study published in the medical journal BMJ Open, the number of siblings you have—and where you fall in the family lineup—can make you more likely to have a heart attack or other cardiovascular event. As the researchers note, "The number and rank order of siblings could be of importance for risk of cardiovascular disease and mortality." For the full story of this emerging connection between family size and your heart, read on.

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Having no siblings or a lot of siblings may be bad news for your heart.

man experiences heart attack while sitting alone in his bedroom with a bottle of whiskey.

The large-scale study, which was conducted out of Sweden, looked at data on 1.36 million men and 1.32 million women born between 1932 and 1960 from the Multiple-Generation Register in Sweden in 1990 and then looked at data on both fatal and non-fatal heart incidents among them for the next 25 years. What the researchers found was that men with one or two siblings had a lower risk of cardiovascular events than only children. However, you can have too much of a good thing, seeing as those with four or more siblings had a higher risk.

Similarly, when compared with others without brothers or sisters, women with three or more siblings had an increased risk of cardiovascular events and those with two or more siblings had an increased risk of coronary events.

But being the first born may be good news for your heart.

newborn baby in the hospital

The researchers found out that first-born children are less prone to non-fatal heart attacks and strokes than their siblings who are born later on. "Being first born is associated with a favorable effect on non-fatal cardiovascular and coronary events for both men and women," the study authors conclude.

Risk for coronary heart disease increased with birth order, peaking at a 23 percent higher risk for men who were fifth-born and 22 percent for fifth-born women, WebMD reports.

Study author Peter Nilsson, MD, PhD, professor of clinical cardiovascular research at Lund University in Sweden, told WebMD that the findings show that, in addition to genetics, social dynamics and early influences can play a part in your heart health. The reduced risk for first-born siblings, Nilsson said, might be because new parents tend to be hyper-focused on their first child's well-being before new babies arrive. "The parents try to supervise everything, but the third and fourth born have less supervision, so they might tend to smoke more, drink more than the first born," he said, citing behaviors that could ultimately affect their health.

In addition to the increased attention, Nilsson told The Telegraph, "To be a first-born means that you are expected to behave more correctly and avoid bad things (alcohol overuse, drugs, tobacco)."

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Your family makeup may also shape your risk of premature death.

Asian elderly senior adult women (twin sisters) using mobile tablet

There was also a pattern when researchers looked at mortality. Women with at least one sibling had a lower risk of death, while men with two or more siblings did.

First-born men had a higher mortality risk than siblings born second or third, while first-born women had a higher risk of death than second-born siblings, but their risk was equal to siblings born third or later.

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However, it's hard to draw a clear line between family dynamics and heart health.

scientists in lab

Considering the new study was observational, the authors cannot attribute a definitive reason as to why bigger families seemed to be connected to more heart-related illnesses. And while the Swedish data didn't include lifestyle factors that could play a role in the health of the subjects studied, like smoking and eating habits, they did consider socioeconomic status, obesity, diabetes, chronic lung disease (COPD), and alcoholism and liver disorders that can come with it. Nilsson told WebMD that while the conventional heart health risk factors are of the utmost importance, "family history still plays a very important role."

"More research is needed to understand the links between sibling number and rank with health outcomes," the authors wrote in their report. "Future research should be directed to find biological or social mechanisms linking the status of being first born to lower risk of cardiovascular disease."

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John Quinn
John Quinn is a London-based writer and editor who specializes in lifestyle topics. Read more
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