This chapter shows that lower intelligence test scores from early life are associated with earlier death, an increased risk of specific diseases, and less advantageous health-related behaviors. It discusses most impressive and informative cohorts that have contributed to cognitive epidemiology. Some of the cohort studies include the Scottish mental surveys of 1932 and 1947, Swedish Conscripts Study, Vietnam Experience Study, and West of Scotland Twenty-07 study. A number of other cohorts have been used in fewer cognitive epidemiology studies. These include the Aberdeen Children of the 1950s study, the Dunedin Birth Cohort, the USA's Termites study, and the Newcastle Thousand Families study. More studies are required that have early life intelligence data, and then have health relevant variables assessed across the life course, and then follow-up to mortality. Theoretical suggestions such as the system integrity hypothesis need to be tested more thoroughly and with better delineation of the constructs.