Demographic transition refers to the shift in vital rates within population groups at various geographical scales from a pattern of high birth (fertility) and death (mortality) rates to one of low rates. Epidemiologic(al) transition, a somewhat more recent concept, considers patterns of mortality change and causes of death (and sometimes ill health) from patterns dominated by infectious diseases to those in which chronic, degenerative physical ailments predominate, and increasingly mental ill‐health conditions, including dementias. Paralleling both these transitions are recognized related changes such as “nutrition transition” and aging transition. All these patterns are evident internationally, regionally, and locally, but it is recognized that they may not be unidirectional. Indeed, different “speeds” of transition may occur in different places and sometimes reverses or mixed patterns may be observed.