Things that can raise blood pressure: eating too much salt, stress ... having a little brother?
A new study of Bolivian villagers shows a link between having a younger brother and slightly increased blood pressure levels later on in adulthood, though the Brandeis University researchers did note that the effect seemed to diminish with age.
Researchers analyzed the systolic and diastolic blood pressure levels of 374 people of Amazonian descent between the ages of 16 and 60, who came from 13 villages in Bolivia. They also took note of what the study participants' birth order was -- whether they were the oldest or youngest, had siblings, etc.
They found that the study participants who reported having a younger brother had as much as 5.9 percent higher systolic and diastolic blood pressure levels, than those who didn't have a younger brother.
Blood pressure levels were also slightly increased for people with a younger sister, though not as much as those with younger brothers -- they had 3.8 percent higher systolic blood pressure levels than those without younger sisters.
Therefore, "in a large family, the number of younger brothers may exert an impact on an individual's blood pressure," the researchers wrote in the Economics and Human Biology study.
LiveScience pointed out that the effect may have less to do with the younger siblings being annoying (though, we would believe it...) but rather with the fact that younger siblings need more attention from parents.
"If there are more siblings in the family, the parents' resources are limited. The older brother will see the younger brother as a competitor and it will kind of stress them out," study researcher Wu Zeng told LiveScience.
That's not to say that siblings can't be good for your health in other ways. An earlier study in the Journal of Family Psychology showed that having a sister is linked with fewer feelings of loneliness, self-consciousness, fear and guilt, Brigham Young University researchers found.
And having a brother or a sister seemed to influence neighborliness, likelihood of doing good deeds and feelings of charitableness, they found.
"For parents of younger kids, the message is to encourage sibling affection," study researcher Laura Padilla-Walker said in a statement. "Once they get to adolescence, it's going to be a big protective factor."