human life span is about 100 years, and there is evidence that around the 50th birthday, people begin to consider their mortality and pay more attention to their health.34
Improvements in methods of health promotion and disability prevention for people over the age of 50—including improvements in the car and advice given by health professionals—could yield major dividends in the form of physical, mental, and social well-being with reduced functional disability, a shortened term of expensive medical services, and a postponement of long-term care. It is only within recent years that older populations have been the focus of research in the field of health promotion and disease and disability prevention.7,20,25,35,38 Indeed, there is little agreement about what health promotion and disability prevention means for the health of persons over the age of 50. Even when related data have been available, there have been few analyses that draw inferences for older populations, little effort to quantify the benefits of such programs, and no consensus on what the evidence might mean for research and clinical practice among those aged 50 and older.9,13,48 In addition, there has been no systematic consolidation of the literature on rehabilitation practices in older populations with that on health promotion and disability prevention. As a result, there is little information on a number of difficult questions for the over-50 age group.6,21,45 For example, what age groupings or functional categories should be developed for this group to target health promotion and disability prevention interventions more effectively? What is known about the effects of such risk factors as smoking, high blood pressure, oral diseases, poor nutrition, and inactivity on different age segments of this population? What are the mechanisms and intervening processes that result in undesirable health effects or losses of functional ability?
Prevention of premature disability and mortality for older individuals requires greater understanding of the changes in risk factors for these groups. Thus, one of the most significant problems facing those who would design interventions for the older population is the lack of an updated risk factor knowledge base. Most risk factor research has involved either the general population, the young, or the middle-aged.7,38,56 There have been few systematic studies of special risks, high or low, among those aged 50 and older.9,12 In addition, there are serious shortcomings in knowledge about the mutability of behaviors already classified as risks.10,32
The relative lack of knowledge on risk factors for those over 50 had led to several major efforts to acquire more longitudinal cohort data. The ongoing Framingham studies33 and the longitudinal research known as the Alameda County studies are being used to