Background Osteoarthritis is the most common joint disease and a massive public health problem worldwide. Incidence rates of OA reported in the literature vary widely. Several studies predicted that OA burden would increase due to population aging and increasing prevalence of obesity. However, population data on trends in OA incidence are extremely limited.
Objectives The purpose of the study was to describe trends in crude, age-specific and age-adjusted incidence of physician-diagnosed OA for men and women in British Columbia, Canada, between 2001 and 2012.
Methods A random sample of 742,070 records was obtained from Population Data BC, an administrative database which covers virtually all hospitalizations and visits to health professionals in the province of British Columbia, Canada since 1986. Similar to prior studies [1,2], we defined incident OA as a hospital discharge or two visits to a health professional (within 2 years and not on the same day) with a diagnostic code for OA (715 in ICD-9 or M15-M19 in ICD-10) in a person without OA within the previous 10 years. Person-years were obtained from individual data on registration with the provincial health plan. The 2006 BC population was used for standardization of rates. Confidence intervals were estimated as exact Poisson intervals and p-values for trend were obtained using a Poisson regression model with a linear year effect.
Results Crude OA incidence rate in the population (men and women combined) rose from 7.1 (95% CI 6.9–7.4) per 1000 person-years in 2001 to 10.2 (9.9–10.4) per 1000 p-y in 2012. The rates were higher in women and increased in both men (5.9 to 8.7 per 1000 p-y) and women (8.4 to 11.5 per 1000 p-y). Age-specific rates increased significantly (p<0.05) among those aged 40–49 and 50–59 in both sexes. Age-standardized rates for selected years are shown in Table 1. A significant upward linear trend between 2001 and 2012 was observed for men (p<0.001) and women (p=0.008).
Conclusions The study confirms an upward trend in crude OA incidence rates in BC observed in prior studies [1,2]. Unlike prior studies, which covered a shorter period, current data show a significant trend in age-standardized incidence in both men and women. This could be due to an increase in obesity prevalence in BC . Our data also show an increase in OA incidence in relatively young persons (40–59), which has not been previously reported. A limitation of the study is the definition of OA based on administrative data.
Rahman MM, Cibere J, Goldsmith CH, Anis AH, Kopec JA. Osteoarthritis incidence and trends in administrative health records from British Columbia, Canada. J Rheumatol. 2014;41(6):1147–54.
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Gotay CC, Katzmarzyk PT, Janssen I, Dawson MY, Aminoltejari K, Bartley NL. Updating the Canadian obesity maps: an epidemic in progress. Can J Public Health. 2012;104(1):e64–8.
Acknowledgement The study was supported by a grant from the Canadian Institutes of Health Research.
Disclosure of Interest None declared