Researchers noted that these findings show just how interdependent, emotionally and physically, long-term couples can become and suggest a greater need for holistic healthcare approaches. In other words treat the couple not just the individual.
Researchers are not sure if this mimicking behavior is specific to long-term married couples and whether this would happen with Baby Boomers with more diverse relationship histories, including divorces and remarriages.
You read of stories where one spouse dies and the other spouse dies shortly after. You come to find these were often long marriages where neither was apart from the other very long. So maybe The Wedding Song is right where one line reads "Oh, a man shall leave his mother, and a woman leave her home. They will travel on to where the two will be as one."
Perhaps we really become one in more ways than we know.