The evidence has been slowly coming in for a while, of course, but recent articles have helped to publicly put the pieces together for us. For example, consider a recent article in Reuters titled "Double the trouble when divorced parents get old."
In broad strokes, marriage is and has been an important institution for us. Not only does it order our daily lives, but it organizes our longtime finances as well. On the other hand, divorced persons simply have to plan that much more for their own old age, especially when it comes to the question of living alone and perhaps shouldering medical care by yourself.
More often than not, this actually is an issue for the adult children of divorced parents. After all, it's already an era that calls for more and more care from children, but taking care of Mom and Dad is an entirely different concept when they are no longer together or there for each other.
Takeaway: for divorced individuals, this is simply something more to consider in your planning for the future, and for families this is a necessary issue to address.
Reference: Reuters (October 22, 2012) "Double the trouble when divorced parents get old"