Ethnic and Environmental Variations In the Prevalence of Osteoporosis...continued.

Geography

According to FAO/WHO and Nutritionists, verbatim.

Villa, M.L. & Nelson, L. 1996. Race, ethnicity and osteoporosis. In: Osteoporosis. Marcus, R., Feldman, D., Kelsey, J., eds. p. 435-447. San Diego: Academic Press.

There are wide geographical variations in hip fracture incidence, which cannot be accounted for by ethnicity. In the United States, the age-adjusted incidence of hip fracture in Caucasian women aged 65 and over varied with geography but was high everywhere – ranging from 700 to 1000 per 100 000 per year.

Bacon, W.E., Maggi, S. & Looker, A. 1996. International comparison of hip fracture rates in 1988-89. Osteoporos. Int., 6: 69-75.

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.

Within Europe, the age-adjusted hip fracture rates ranged from 280 to 730 per 100 000 women in one study and from 419 to 545 per 100 000 in another study in which the comparable rates were 52.9 in Chile, 94.0 in Venezuela, and 247 in Hong Kong.

Johnell, A., Gullberg, B., Allander, E. & Kanis, J.A. 1992. The apparent incidence of hip fracture in Europe: A study of national register sources. Osteoporos. Int., 2: 298-302.

In another study age-adjusted hip fracture rates in women in 12 European countries ranged from 46 per 100 000 per year in Poland to 504 per 100 000 in Sweden, with a marked gradient from south to north and from poor to rich.

Xu, L., Lu, A., Zhao, X., Chen, X. & Cummings, S.R. 1996. Very low rates of hip fracture in Beijing, People's Republic of China: the Beijing Osteoporosis Project. Am. J. Epidemiol., 144: 901-907.

In Chinese populations, the hip fracture rate is much lower in Beijing (87–97 per 100 000) than in HongKong (181–353 per 100 000), where the standard of living is higher. Thus there are marked geographic variations in hip fracture rates within the same ethnic groups.

Ethnicity, environment, and lifestyle

Hegsted, D.M. 1986. Calcium and osteoporosis. J. Nutr., 116: 2316-2319.

The conclusion from the above is that there are probably ethnic differences in hip fracture rates within countries but also environmental differences within the same ethnic group which may complicate the story. For international comparisons on a larger scale, it is impossible to separate genetic from environmental factors, but certain patterns emerge which are likely to have biological meaning. The most striking of these is the positive correlation between hip fracture rates and standard of living noted by Hegsted when he observed that osteoporosis was largely a disease of affluent Western cultures.

Gallagher, J.C., Melton, L.J., Riggs, B.L. & Bergstrath, E. 1980. Epidemiology of fractures of the proximal femur in Rochester, Minnesota. Clin Orthop., 150: 163-171.

He based this conclusion on a previously published review of hip fracture rates in 10 countries,

Maggi, S., Kelsey, J.L., Litvak, J. & Heyse, S.P. 1991. Incidence of hip fractures in the elderly. A cross-national analysis. Osteoporos. Int., 1: 232-241. 

which strongly suggested a correlation between hip fracture rate and affluence. Another review of 19 regions and racial groups

Xu, L., Lu, A., Zhao, X., Chen, X. & Cummings, S.R. 1996. Very low rates of hip fracture in Beijing, People's Republic of China: the Beijing Osteoporosis Project. Am. J. Epidemiol., 144: 901-907. 

confirmed this by showing a gradient of age- and sex-adjusted hip fracture rates from 31 per 100 000 in South African Bantu to 968 per 100 000 in Norway. In the analysis of hip fracture rates in Beijing and Hong Kong referred to above, it was noted that the rates in both cities were much lower than in the United States. Many other publications point to the same conclusion – that hip fracture prevalence (and by implication osteoporosis) is related to affluence and, consequently, to animal protein intake, as Hegsted pointed out, but also and paradoxically to calcium intake.

The calcium paradox

Hegsted, D.M. 1986. Calcium and osteoporosis. J. Nutr., 116: 2316-2319

The paradox that hip fracture rates are higher in developed nations where calcium intake is high than in developing nations where calcium intake is low clearly calls for an explanation. 

FAO/WHO

Hegsted was probably the first to note the close relation between calcium and protein intakes across the world

63. Nordin, B.E.C. & Polley, K.J. 1987. Metabolic consequences of the menopause. A crosssectional, longitudinal, and intervention study on 557 normal postmenopausal women. Calcif. Tissue Int., 41: S1-S60.

(which is also true within nations [63])

Feskanich, D., Willett, W.C., Stampfer, M.J. & Colditz G.A. 1996. Protein consumption and bone fractures in women. Am. J. Epidemiol., 143: 472-479.

and to hint at but dismiss the possibility that the adverse effect of protein might outweigh the positive effect of calcium on calcium balance. Only recently has fracture risk been shown to be a function of protein intake in American women.

Nordin, B.E.C. 1997. Calcium in health and disease. Food, Nutrition and Agriculture, 20: 13-24.

There is also suggestive evidence that hip fracture rates (as judged by mortality from falls in elderly people across the world) are a function of protein intake,national income, and latitude.

Aaron, J.E., Gallagher, J.C., Anderson, J., Stasiak, L., Longton, E.B. & Nordin, B.E.C. 1974. Frequency of osteomalacia and osteoporosis in fractures of the proximal femur. Lancet, 2: 229-233.

Aaron, J.E., Gallagher, J.C. & Nordin, B.E.C. 1974. Seasonal variation of histological osteomalacia in femoral neck fractures. Lancet, 2: 84-85.

Baker, M.R., McDonnell, H., Peacock, M. & Nordin, B.E.C. 1979. Plasma 25- hydroxy vitamin D concentrations in patients with fractures of the femoral neck. Br. Med. J., 1: 589.

Morris, H.A., Morrison, G.W., Burr, M., Thomas, D.W. & Nordin, B.E.C. 1984. Vitamin D and femoral neck fractures in elderly South Australian women. Med. J. Aust., 140: 519-521.

Von Knorring, J., Slatis, P., Weber, T.H. & Helenius, T. 1982. Serum levels of 25- hydroxy vitamin D, 24,25-dihydroxy vitamin D and parathyroid hormone in patients with femoral neck fracture in southern Finland. Clin. Endocrinol., 17: 189-194.

Pun, K.K., Wong, F.H. & Wang, C. 1990. Vitamin D status among patients with fractured neck of femur in Hong Kong. Bone, 11: 365-368.

Lund, B., Sorenson, O.H. & Christensen, A.B. 1975. 25-hydroxycholecalciferol and fractures of the proximal femur. Lancet, 2: 300-302. 

According to said Nutritionists,,,verbatim.

The latter is particularly interesting in view of the strong evidence of vitamin D deficiency in hip fracture patients in the developed world

Chapuy, M.C., Arlot M.E. & Duboeuf, F. 1992. Vitamin D3 and calcium to prevent hip

fractures in elderly women. N. Engl. J. Med., 327: 1637-1642.

Boland, R. 1986. Role of vitamin D in skeletal muscle function. Endocr. Revs., 7: 434-448.

and the successful prevention of such fractures with small doses of vitamin D and calcium (see Chapter 8).

 FAO/WHO

It is therefore possible that hip fracture rates may be related to protein intake, vitamin D status, or both and that either of these factors could explain the calcium paradox. We shall therefore consider how these and other nutrients (notably sodium)affect calcium requirement.