Women who marry significantly younger men, or significantly older men, have a shorter life expectancy than women who wed males about their own age, according to new findings by German scientists.
Previous studies showed that men with younger wives live longer. For years, researchers thought that this data was true for both sexes.
They assumed that an effect called "health selection" was in play - those who select younger partners are able to do so because they are healthier and thus already have a higher life expectancy.
It was also thought that a younger spouse has a positive psychological and social effect on an older partner and can be a better caretaker in old age, thereby helping to extend the partner's life.
In a new study, however, Dr Sven Drefahl of the Max Planck Institute for Demographic Research (MPIDR) in Rostock, Germany, has shown that the same is not true for women.
The greater the age difference from the husband, the lower the wife's life expectancy, regardless of whether the woman is younger or older than her spouse.
"These theories now have to be reconsidered," Drefahl says. "The reasons for mortality differences due to the age gap of the spouses remain unclear."
Using data from almost two million Danish couples, Drefahl was able to eliminate the statistical shortcomings of earlier research, and showed that the best choice for a woman is to marry a man of exactly the same age.
An older husband shortens her life, a younger one even more so. According to Drefahl's study, published in the journal Demography, women marrying a partner seven to nine years younger increase their mortality risk by 20 percent. Hence, "health selection" can't be true for women.
It is also doubtful that older wives benefit psychologically and socially from a younger husband. This effect only seems to work for men.
While many studies on mate selection show that women mostly prefer men the same age, most of them end up with an older husband.
"On average, men have fewer and lesser quality social contacts than those of women," Drefahl says.
Thus, unlike the benefits of a younger wife, a younger husband wouldn't help extend the life of his older wife by taking care of her, going for a walk with her and enjoying late life together. She already has friends for that. The older man, however, doesn't.
The question that remains is why a younger partner would actually shorten a woman's life. "One of the few possible explanations is that couples with younger husbands violate social norms and thus suffer from social sanctions," Drefahl says.
Since marrying a younger husband deviates from what is regarded as usual, these couples could be considered outsiders and receive less social support. This could result in a less joyful and more stressful life, reduced health and finally, increased mortality.
While the new MPIDR study shows that marriage disadvantages most women when they are not the same age as their husband, it is not true that marriage in general is unfavorable.
Being married appears to raise the life expectancy of both men and women above those that are unmarried.
