There's a brilliant interview with the co-author of The Longevity Project on NPR this week. They mention a lot about the effects of marriage and relationships on a person's lifespan and one of the interesting things was that the health of a marriage is oftentimes dependent on the health of the MAN. In other words, the woman can be healthy or unhealthy and it won't make much of a difference on lifespan, but if the man is unhealthy, it can play a detrimental role on not his lifespan, but hers as well.
The study also determined that marriage is more necessary for men than for woman. I completely agree. Men tend to gain much more from marriage whereas woman tend to lose more.