Ethnic and Environmental Variations In the Prevalence of Osteoporosis

FAO/WHO Expert Group. 1962. Calcium Requirements. Rome, FAO.

Thacher, T.D., Fischer, P.R. & Pettifor, J.M. 1999. A comparison of calcium, vitamin D, or both for nutritional rickets in Nigerian children. N. Engl. J. Med.. , 341: 563-568.

Intakes of calcium have been known for many years to vary greatly from one country to another, as is clearly shown in FAO food balance sheets (Table 30). Until fairly recently, it was widely assumed that low calcium intakes had no injurious consequences.

This view of the global situation underlay the very conservative adequate calcium intakes recommended by WHO/FAO in 1962. At that time, osteoporosis was still regarded as a bone matrix disorder and the possibility that it could be caused by calcium deficiency was barely considered. The paradigm has changed since then. 

Calcium deficiency is taken more seriously than it was and the apparent discrepancy between calcium intake and bone status across the world has attracted more attention. In general, recent investigations have sought for evidence of low bone density and high fracture incidence in countries where calcium intake is low; rickets has not been looked for, but the low calcium rickets recently reported from Nigeria will no doubt attract attention.

Eddy, T.P. 1972. Deaths from domestic falls and fractures. Br. J. Prev. Soc. Med., 26: 173-179.

This issue can be considered at several levels. The first level is genetic: Is there agenetic (ethnic) difference in the prevalence of osteoporosis between racial groups within a given society? The second level might be termed environmental-cultural (e.g., dietary): Is there a difference in the prevalence of osteoporosis between national groups of similar ethnic composition? The third level is environmental-geographical (e.g., latitude, affluence, and lifestyle): Is there a difference in the prevalence of osteoporosis between countries regardless of ethnic composition? 

At each of these levels, the prevalence of osteoporosis can in theory be determined in at least two ways – from the distribution of bone density within the population and from the prevalence of fractures, notably hip fractures. In practice, hip fracture data (ormortality from falls for elderly people which has been used as a surrogate are more readily available than bone densitometry.

Ethnicity

Trotter, M., Broman, G.E. & Peterson, R.R. 1960. Densities of bones of white and Negro skeletons. J. Bone Joint Surg. 1960;42-A:50-59.

Solomon, L. 1968. Osteoporosis and fracture of the femoral neck in the South African Bantu. J. Bone Joint Surg., 50-B-2:2-13.

Bollet, A.J., Engh, G. & Parson, W. 1965. Sex and race incidence of hip fractures. Arch. Internal Med., 116:191-194.

Comparisons between racial groups within countries suggest substantial racial differences in the prevalence of osteoporosis. This was probably first noted by Trotter when she showed that bone density (weight/volume) was significantly higher in skeletons from black than from Caucasian subjects in the United  States. It was later shown that hip fracture rates were lower in blacks than Caucasians in South Africa and the United States.

Cohn, S.H., Abesamis, C., Yasumara, S., Aloia, J.F., Zanzi, I. & Ellis, K.J. 1977. Comparative skeletal mass and radial bone mineral content in black and white women. Metabolism, 26: 171-178.

DeSimone, D.P., Stevens, J., Edwards, J., Shary, J., Gordon, L. & Bell, N.H. 1989. Influence of body habitus and race on bone mineral density of the midradius, hip, and spine in aging women. J. Bone Miner. Res., 5: 827-830.

Bell, N.H., Shary, J., Stevens, J., Garza, M., Gordon, L. & Edwards, J. 1991. Demonstration that bone mass is greater in black than in white children. J. Bone Miner. Res., 6: 719-723.

Nelson, D.A., Jacobsen, G., Barondess, D.A. & Parfitt, A.M. 1995. Ethnic differences in regional bone density, hip axis length, and lifestyle variables among healthy black and white men. J. Bone Miner. Res., 10: 782-787. 

According to said authors...verbatim.

These observations have been repeatedly confirmed without being fully explained but appear to be genetic in origin because the difference in bone status between blacks and Caucasians in the United States is already apparent in childhood and cannot be explained by differences in body size. The difference in fracture rates between blacks and Caucasians cannot be explained by differences in hip axis length; it seems to be largely or wholly due to real differences in bone density.

Cund, T., Cornish, J., Evans, M.C., Gamble, G., Stapleton, J. & Reid, I.R. 1995. Sources of interracial variation in bone mineral density. J. Bone Miner. Res., 10: 368-373.

Comparisons between Caucasians and Samoans in New Zealand have also shown the latter to have the higher bone densities whereas the lower bone densities of Asians than Caucasians in New Zealand are largely accounted for by differences in body size.

Cummings, S.R., Cauley, J.A., Palermo, L., Ross, P.D., Wasnich,R.D., Black, D. & Faulkner, K.G. 1994. Racial differences in hip axis lengths might explain racial differences in rates of hip fracture. Osteoporos. Int., 4: 226-229.

Cummings, S.R., Cauley, J.A., Palermo, L., Ross, P.D., Wasnich,R.D., Black, D. & Faulkner, K.G. 1994. Racial differences in hip axis lengths might explain racial differences in rates of hip fracture. Osteoporos. Int., 4: 226-229.

In the United States, fracture rates are lower among Japanese than among Caucasians but may be accounted for by their shorter hip axis length and their lower incidence of falls.

Yano, K., Wasnich, R.D., Vogel, J.M. & Heilbrun, L.K. 1984. Bone mineral measurements among middle-aged and elderly Japanese residents in Hawaii. Am. J. Epidemiol., 119: 751-764.

Ross, P.D., He, Y-F. & Yates, A.J. 1996. Body size accounts for most differences in bone density between Asian and caucasian women. Calcif. Tissue Int., 59: 339-343.

Bone density is generally lower in Asians than Caucasians within theUnited States but this again is largely accounted for by differences in body size. 

Silverman, S.L. & Madison, R.E. 1988. Decreased incidence of hip fracture in Hispanics, Asians, and blacks: California hospital discharge data. Am. J. Public Health, 78: 1482-1483.

Lauderdale, D.S., Jacobsen, S.J., Furner, S.E., Levy, P.S., Brody, J.A. & Goldberg, J. 1997. Hip fracture incidence among elderly Asian-American populations. Am. J. Epidemiol., 146: 502-509. 

There are also lower hip fracture rates for Hispanics, Chinese, Japanese, and Koreans than Caucasians in the United States. The conclusion must be that there are probably genetic factors influencing the prevalence of osteoporosis and fractures, but it is impossible to exclude the role of differences in diet and lifestyle between ethnic communities within a country.