Why twin studies are important for health span science research: the case of maltreatment of aging adults.

Average life expectancies have lengthened across human history. As a result, there is an increased need to care for a greater number of individuals experiencing common age-related declines in health. This has helped to spur a rapidly increasing focus on understanding "health span", the portion of the life-course spent functionally healthy. Yet to penetrate the science of health span, however, is a topic which seems fundamental to the ability to age in functional and healthy ways, and has received considerable attention in other fields. As more of the population ages, the risk of exposure to abuse and neglect among older citizens not only rises, but can manifest as both cause and effect of declining health span. Among our goals here is to make a case for including this subject among the other central components of health span science. In so doing, we also outline reasons why quantitative genetic designs using samples of twins can be a versatile tool for improving causal inference when studying maltreatment among older persons specifically, but also on a range of other health span topics in general.