Data for successive population surveys show there is a sustained increase in the prevalence of arthritis, surpassing projected estimates. We examined whether the often-made assumption of stability in age/sex-specific arthritis point-prevalence estimates when estimating future burden is upheld; we used nearly a decade of survey data, and computed new projections for arthritis prevalence in Canada, taking into account past changes in age/sex-specific prevalence estimates and anticipated changes in the age/sex structure of the population. The prevalence from 1994 to 2003, overall and by age and sex, was documented.
Analyses were based on persons aged 15+ years from 3 cycles of the National Population Health Survey (1994-99; n › 14,000) and 2 cycles of the Canadian Community Health Survey (2000-03; n › 130,000). Two projection scenarios were adopted to estimate future burden.
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Stability in age/sex point-prevalence estimatesi was not observed. From 1994 to 2003, absolute and relative increases were greatest in the older age groups (55+ yrs) and younger age groups (25-54 yrs), respectively. By 2021, we anticipate the prevalence of arthritis in Canada will have increased to between 21% and 26%. Overall, the prevalence increased from 13.4% to 17.6% from 1994 to 2003, an increase of nearly 50% in the number of Canadians reporting arthritis.
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The assumption of stable age/sex prevalence estimates over time does not hold in Canada. Past projections have underestimated future burden; past trends need to be considered.
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| Prevalence (%) (95% confidence interval) | ||||||
|---|---|---|---|---|---|---|
| 1994ii | 1996iii | 1998iv | 2000v | 2002vi | ||
| Overall | 13.42 | 14.50 | 15.98 | 16.00 | 17.63 | |
| (12.8, 14.1) | (14.0, 15.0) | (15.2, 16.7) | (15.7, 16.3) | (17.3, 18.0) | ||
| Ages | 15-24 | 1.8 | 1.7 | 1.3 | 2.2 | 1.9 |
| (1.1, 2.5) | (1.1, 2.3) | (0.7, 2.0) | (1.9, 2.5) | (1.6, 2.2) | ||
| 25-34 | 3.5 | 4.0 | 3.8 | 4.7 | 4.3 | |
| (2.7, 4.3) | (3.3, 4.6) | (2.9, 4.7) | (4.3, 5.2) | (3.8, 4.8) | ||
| 35-44 | 6.8 | 7.7 | 8.5 | 8.8 | 9.1 | |
| (5.7, 7.9) | (6.8, 8.6) | (7.2, 9.8) | (8.3, 9.3) | (8.5, 9.7) | ||
| 45-54 | 13.9 | 15.3 | 17.2 | 17.1 | 19.5 | |
| (12.3, 15.6) | (13.9, 16.6) | (15.2, 19.3) | (16.3, 17.9) | (18.6, 20.3) | ||
| 55-64 | 27.2 | 28.5 | 32.6 | 29.8 | 31.8 | |
| (24.7, 29.6) | (26.5, 30.4) | (29.7, 35.6) | (28.7, 31.0) | (30.7, 32.8) | ||
| 65-74 | 37.5 | 39.7 | 42.1 | 39.9 | 44.2 | |
| (35.1, 40.0) | (37.9, 41.4) | (38.9, 45.4) | (38.5, 41.3) | (42.9, 45.4) | ||
| 75+ | 45.4 | 46.8 | 48.5 | 47.5 | 51.5 | |
| (42.3, 48.5) | (44.7, 48.9) | (45.0, 52.1) | (46.0, 49.1) | (50.1, 52.8) | ||
| Sex | Men | 10.1 | 10.2 | 11.8 | 12.0 | 13.3 |
| (9.3, 11.0) | (9.6, 10.9) | (10.8, 12.8) | (11.6, 12.4) | (12.8, 13.7) | ||
| Women | 16.6 | 18.7 | 20.0 | 19.8 | 21.8 | |
| (15.7, 17.5) | (17.9, 19.4) | (18.9, 21.2) | (19.4, 20.3) | (21.3, 22.3) | ||
| Total Number | 3,033,000 | 3,399,000 | 3,797,000 | 3,921,000 | 4,452,000 | |
The prevalence of self-reported arthritis/rheumatism in the Canadian population aged 15+ years from 1994 to 2002 is presented in Table 1. Over these years, the prevalence increased by more than 4 percentage points (difference = 4.2; 95% CI 3.46-4.94; p‹0.01), from 13.4 to 17.6 represented by an increase of nearly 50% of people reporting these conditions.
Results from linear regression analysis (data not shown) revealed a cubic relationship between prevalence and age. As well, a significant relationship between sex and age was found, with the increasing prevalence with increasing age being greater among women. Figure 1 shows observed (2002) and predicted (2006-21) age/sex specific estimates, showing continued growth in the middle years of life and in older women.
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