She was just 17. Richard Trimmer married Nancy Hoke in 1951 and for the next six decades the Trimmer family grew. The couple had six children and 10 grandchildren. They were great grandparents more than a dozen times over.

And then, this Sunday, after more than 60 years together, the Trimmers died as they had lived: Inseparable.

Nancy went first. She passed in her sleep. Richard, away in the hospital being treated for terminal lung cancer, followed her just a few hours later.

"It was all just getting too hard, so God took care of it," their daughter-in-law, Sue Trimmer told Pennsylvania's Evening Sun on Tuesday.

God, perhaps, but there is a science to these things, and it goes a long way in explaining what happened to the Trimmers.

"Morbidity and mortality rates from all diseases increase, especially with geriatrics," when they are depressed or bereaved, Dr. Richard Kaplan, a psychiatrist at North Shore-Long Island Jewish's Syosset Hospital, told ABC News.

"Part of the real issue is the stress," Kaplan said. "The work of taking care of an sick spouse is a tremendous burden, even for younger people. But when you start to deal with all the frailties of the geriatric, things that appear happenstance are that much more likely."

The Trimmers' case is, indeed, rare. They died less than 12 hours apart. But in a study released last month, the American Heart Association found that the risk of suffering a heart attack increased by 21 times  in the first 24 hours after the death of a loved one.

In May, 2007, a University of Glasgow study found that the "bereaved were at higher risk than non-bereaved of dying from any cause." Tracking 4,395 married couples aged 45-64 years old, researchers determined that the danger to widows and widowers increased by 30 percent in the six months following a spouse's death.

Nancy Trimmer had required open heart surgery ten years ago, the Evening Sun reported, making her even more vulnerable to the sadness she had experienced when her husband left home for the hospital.

Most studies agree that the odds roll back in the favor of the surviving partner as time goes by. New research has been focused, Kaplan said, on "how to handle depression related to [the long term bereaved]."

"Recent work indicated depression is depression in any case, even if it's predictable," he said. Psychiatrists had in the past been hesitant to diagnose the elderly, but attitudes and protocol are likely to change with the release newest Diagnostic and Statistical Manual of Mental Disorder (DSM V).