An epidemiological model of privational rickets and osteomalacia

Privational infantile rickets is now rare in the UK.Privational vitamin D deficiency remains common in the British Asian population, leading to neonatal, infantile and late rickets in childhood and osteomalacia (adult rickets) in Asian women (Dunnigan et al. 1962; Ford et al. 1972a Ford et al. , 1973;;Holmes et al. 1973;Stamp et al. 1980).The prevalence of these manifestations of severe vitamin D deficiency in the Asian population has declined in the last 25 years.In the white population, privational osteomalacia is virtually confined to advanced old age (Gough et al. 1964;Anderson et al. 1966;Chalmers et al. 1967).The advent of privational Asian rickets and osteomalacia to Britain in the 1960s offered an opportunity to re-examine the environmental factors which determine these diseases.The present paper describes the development of a risk-factor model for Asian privational rickets and osteomalacia based on examination of the relative roles of limited exposure to U.V. radiation ( W R ) and dietary factors in their aetiology (Robertson e f al. 1982;Henderson et al. 1987Henderson et al. , 1990)).The model provides an explanation for trends in the prevalence of privational rickets and osteomalacia in the UK in the present century and for the current prevalence of these diseases in the UK and in many underdeveloped Third World countries where they remain common (Dunnigan et al. 1982). RISK FACTORS FOR ASIAN RICKETS AND OSTEOMALACIA: EARLY OBSERVATIONSThe discovery of late rickets and osteomalacia in the Glasgow Muslim community in 1961 (Dunnigan et al. 1962) was followed by a study of 7 d weighed dietary intakes in rachitic and normal Muslim schoolchildren and in a control group of white schoolchildren (Dunnigan & Smith, 1965).Surprisingly, the dietary vitamin D intakes of rachitic Asian children, normal Asian children and Glasgow white children were similar.The higher fibre and phytate intakes of the Asian children were not considered aetiologically significant.Studies of daylight outdoor exposure showed no significant differences between the summer and non-summer exposures of rachitic and normal Muslim schoolchildren or between Muslim and white schoolchildren (Dunnigan, 1977).These patterns of daylight outdoor exposure did not conform to the Muslim 'purdah' stereotype, although sunbathing was unknown in the Asian community.It was also evident that many Glasgow white schoolchildren went out relatively little, even in fine weather, in a form of 'cultural purdah'.Similar patterns of apparently adequate daylight outdoor exposure were noted in Asian women with privational osteomalacia wearing Western dress in London (Compston, 1979).These observations did not support the hypothesis that Asian rickets and osteomalacia resulted from deficient exposure to UVR or from deficient dietary vitamin D intake relative to white women and children in whom privational rickets and osteomalacia were unknown outside infancy and old age.The suggestion that Asian rickets in the UK might be related to the consumption of unleavened bread was supported by Mellanby's (1949) earlier identification of an anticalcifying factor in oatmeal, subsequently shown to be phytic acid, and by evidence of 'sunshine' rickets in Iranian village children consuming large quantities of unleavened bread (tanok) with abundant exposure to UVR (Rheinhold, 1972).Two uncontrolled trials