Given that grieving spouses are more vulnerable, and that marriage apparently lead to a increased longevity, does the negative affects of spousal grief mitigate the longevity ascribed to marriage? I am sure this must have been excamined in actuarial terms. 
Pure anecdote, but I bet it’s not untypical, supporting the idea that the widowed take less good care of themselves. After my mother died, my dad was kind of rudderless. He overspent, ate poorly, and generally made poor choices. For example, where she would have cooked a healthy supper of broiled chicken and fresh vegetables, he would go to the super market seafood department and buy a lobster, have them steam it for him and take it home to eat with melted butter. He died of advanced cardiovascular disease, but one thing that hastened his demise was that while he would have done whatever Mom told him to do, he would not follow his doctors’ advice. I’m sure had she been around she would have noticed when his foot began developing gangrene, for example, but he ignored it. Eeeew.
To be fair, however, had he gone first, we are pretty sure Mom would have gone back to smoking and drinking, which she enjoyed but gave up after her first valve transplant.
Maybe grieving spouses are more vulnerable, but then again, maybe people tend to hold on longer than they would have, to keep up with a spouse. I don’t think you can say that the tendancy of spouses to die close together implies a tendancy for their deaths to be hastened.