Spatial patterns of osteoporosis in British Columbia (1985-1989) : possible links with sediment geochemistry, lake and drinking water quality
Date
1994
Authors
Zhang, Liping
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Abstract
This geographical study initially seeks to establish spatial patterns of osteoporosis in British Columbia for the period 1985 to 1989. In addition, in an attempt to broaden understanding of the etiology of this disorder, it examines possible relationships between the Hospital Diagnosed Osteoporosis Rates (HDOR) and environmental factors such as sediment geochemistry and lake and drinking water quality.
The data used in this study were obtained from a wide variety of sources, including the BC Ministry of Health and Ministry Responsible for Seniors, BC Ministry of Environment, Lands and Parks, and the BC Ministry of Finance. Data were obtained also from numerous environmental managers who had collected water quality information for a diversity of reasons. In addition, a data bank compiled by Ian Norie and Harold D. Foster for use in an earlier study of digestive cancer and water quality also was utilized.
Unfortunately, difficulties with quality restricted suitable medical data to the period 1985 to 1989. For each year and for the entire period as a whole, the data were used to calculate age standardized hospital diagnosed osteoporosis rates (ASHDORs) and standardized hospital diagnosed osteoporosis ratios (SHDORs). The former were calculated twice using two slightly different methods to remove duplicate cases. Since it was impossible to distinguish new cases (first diagnosed during the period 1985 to 1989) from hospital re-admissions of patients diagnosed as having osteoporosis in 1984 or earlier, the true incidence of the disorder in British Columbia could not be calculated (either as a rate or as a ratio). For this reason the term Hospital Diagnosed Osteoporosis Rate (HDOR), derived from analysis of hospital data, is used throughout this thesis. To identify the significance of the spatial patterns and possible links with the environment, two types of statistical methods of analysis were employed in this study, namely the Chi-Square test (x2) and Pearson correlation.
One major conclusion that can be drawn from the results obtained in this study is that during the period 1985-1989, the Standardized Hospital Diagnosed Osteoporosis Ratio (SHDOR) in British Columbia varied spatially in a statistically significant manner in both genders (Figures 4.1-4.3).
The analyses also clearly demonstrated that in British Columbia, osteoporosis occurred more frequently in women than men with a female to male ratio of 5.46:1. "ASHDOR" also increased markedly with age, particularly in those older than 45.
Although several elements, including calcium, zinc, copper, lead and fluoride have been discussed in the medical literature as having possible roles in the etiology of osteoporosis, the current study was unable to identify any consistent statistically significant relationships between exposure to these elements in sediments, lake or drinking water and the "ASHDORs". In contrast, dissolved aluminum (Al_D) in drinking water repeatedly demonstrated statistically strong positive correlations with "ASHDORs" in both genders and in the population as a whole. The geographical evidence from British Columbia, therefore, tends to suggest that osteoporosis may be related to elevated dissolved aluminum levels in drinking water.
Statistical abberations can produce spurious relationships between disease distributions and the physical environment, which may tend to suggest causal links where none exist. This may, or may not, be the case with osteoporosis and aluminum. Ideally this possible relationship should be tested using the Bradford Hill criteria, which are commonly employed to establish cause and effect. As yet, insufficient research on the topic makes this impossible. Therefore, the best that can be suggested is that the role of aluminum (particularly dissolved aluminum in drinking water) in the etiology of osteoporosis, should be given greater emphasis in future osteoporosis research.