For years, public health researchers have noted that married people live longer, healthier lives. As Rose Hoban reports, one researcher went a step further and examined the impact of children on their parents' health.
Public health researchers have found the so-called "marriage benefit" is stronger for men than it is for women.
Dr. Omar Rahman from the - of about 800 households in several Bangladeshi villages. The information included data on wealth, family structure and health. His hypothesis was that in a male-centered society, the presence of sons would be more important to the health of elderly parents.
"In old age, what do you need?" Rahman asks.
He argues that most older people need some money, and they need someone to look after them.
"Now, in that society, the men control the money until they die," Rahman says. "So they don't need anyone to give them money. They don't need their sons to give them money because they control the land, and they, on average, they're 10 years older than their wives, so their wives are all alive… so they have wives that take care of them."
And indeed, what Rahman found was that for elderly men, the presence of children didn't influence their health or mortality once they became old.
But Rahman found that what kept elderly women healthy was having a daughter. It didn't matter if the daughter lived far away, and it didn't matter if there was also a son. In terms of keeping mothers healthy in old age, simply having a daughter guaranteed better health.
"And what was even more surprising, probably the most surprising thing in our study, was educated daughters seem to matter a lot," he says.
"An older woman, like 60 plus woman, who had a daughter who had at least six years of schooling was three times as likely to say that she was in good health compared to her peer who didn't have a daughter at that level of education," Rahman reports.
He says this strengthens the argument for educating girls. He also says this finding could explain Bangladesh's birth rate. After a precipitous drop in the number of children per household, the birth rate has remained steady at three per family. He suggests this could be because families frequently try for a third child if they don't have a son and daughter already.
He also says he's quite happy to have two daughters of his own.
Rahman presented his study in October at the annual meeting of the American Public Health Association in San Diego, California.