Even though the general health and life expectancies of Western societies have been consistently rising throughout the 20th century, socioeconomic health inequalities continue to persist. Individuals from lower socioeconomic groups have substantially worse health and an increased mortality risk compared to individuals from higher socioeconomic groups. As external factors such as material resources cannot fully account for these health inequalities, personal factors such as intellectual abilities have been suggested as additional important explanatory factors. The research field concerned with the effects of intelligence on different health outcomes is called cognitive epidemiology. Results from this field of research have now established that childhood intelligence is an important predictor of different health outcomes in adulthood. Specifically, children with higher intelligence exhibit a lower mortality risk and enjoy better health in adulthood compared to children with lower childhood intelligence. Despite these findings, several open research questions remain: (1) Almost all previous studies on the relation between childhood intelligence and adult health have been conducted in English-speaking or Scandinavian countries. Can these findings be generalized to countries with different cultural backgrounds, health-care systems, or levels of social mobility? Specifically, Luxembourg offers universal access to quality health care, which may compensate for some of the effects of individual differences in intelligence on health, and as a result, intelligence may lose its impact. (2) Physical health is a multidimensional concept with three distinct subdimensions: a physical subdimension (e.g., presence of diagnosed diseases, number of doctor visits in a certain time period), a subjective subdimension (e.g., satisfaction with one’s own health), and a (social-)functional subdimension (e.g., unimpaired participation in social and occupational activities or performing household tasks). Most previous studies on the ...