A recent study found that younger siblings are at higher risk for heart events than their older counterparts, but people have been doing studies on what birth order affects for years.
A 2017 study found that first-born children are 30 percent more likely to be CEOs or politicians; and a 2014 study found that first-born women end up more ambitious than first-born men. The 2017 study also found that first-borns stay in school longer, make more money, have higher IQ, and spend more time on homework than watching television. There’s also evidence that first-borns are more likely to marry earlier than their siblings, and the odds of a happy marriage are highest when a first-born woman marries a last-born son.
A different study found that later-born children are more likely to have poorer physical and mental health, and were more likely to smoke, compared to their elder siblings. But it’s not all rosy for first-borns. One study found eldest children are four percent more likely to be overweight and two percent more likely to be obese compared to their younger siblings.