Annual incidence, prevalence, and mortality of multiple sclerosis in white South-African-born and in white immigrants to South Africa.
This was the first conclusive demonstration that MS was largely a disease of place, as Dean showed that the rate of MS was markedly reduced in migrants to South Africa (Dean, 1949). This paper followed up his original observation in 1949 based on smaller numbers. The cognitive fallacy, which remains difficult to extinguish, was that diseases were either environmental or genetic. It was only recently that it has become clear that both genes and environment interact to produce susceptibility. Dean’s observation was seminal, and it is indeed a shame he received little recognition for this before his recent death.
Looking back over this paper, it is striking how little has been made of the difference in risk for native Afrikaaners vs. English-speaking residents born in South Africa. This can in retrospect be seen to provide the first clue to the transgenerational effects now apparent.