Mortality from cardiovascular disease among interregional migrants in England and Wales.

OBJECTIVE: To investigate the extent to which geographical variations in mortality from ischaemic heart disease and stroke in Britain are influenced by factors in early life or in adulthood.
DESIGN: Longitudinal study of migrants.
SUBJECTS: 1% sample of residents in England and Wales born before October 1939 and enumerated at the 1971 census (the Office of Population Censuses and Surveys' longitudinal study). MAIN OUTCOME MEASURE: 18,221 deaths from ischaemic heart disease and 9899 deaths from stroke during 1971-88 were analysed by areas of residence in 1939 and 1971. These included 2928 deaths from ischaemic heart disease and 1608 deaths from stroke among individuals moving between 14 areas defined by the major conurbations and nine standard administrative regions of England and Wales.
RESULTS: The southeast to northwest gradient in mortality from ischaemic heart disease was related significantly to both the 1939 area (chi 2 = 6.09, df = 1) and area in 1971 (chi 2 = 5.05, df = 1). Geographical variations in mortality from stroke were related significantly to the 1939 area (chi 2 = 4.09, df = 1) but the effect of area in 1971 was greater (chi 2 = 8.07, df = 1). The effect of 1971 area on mortality from stroke was largely due to a lower risk of death from stroke among individuals moving into Greater London compared with migrants to the rest of the South East region (chi 2 = 4.54, df = 1).
CONCLUSIONS: Geographical variations in mortality from cardiovascular disease in Britain may be partly determined by genetic factors, environmental exposures, or lifestyle acquired early in life, but the risk of fatal ischaemic heart disease and stroke changes on migration between areas with differing mortality. The low risk of death from stroke associated with residence in Greater London is acquired by individuals who move there.