Session Information
Session Type: Abstract Submissions (ACR)
Background/Purpose:
Data on the incidence of osteoarthritis (OA) are limited and there is little information on the trend in incidence of OA over time. The objective of this study was to calculate the incidence rates and to describe the changes in OA incidence rates using two case definitions in 18 years of administrative health records.
Methods:
We analyzed all visits to health professionals and all hospital admission records of a random sample (n = 540,000) from British Columbia, Canada for the fiscal years 1991/92 through 2008/09. Administrative OA was defined in two ways: 1) at least one physician diagnosis or one hospital admission (Def1) and 2) at least two physician diagnoses in two years or one hospital admission (Def2). Incidence rate was defined as the number of new OA cases during a fiscal year divided by the person-years at risk. New adult (age 20 years and older) OA cases were identified for the fiscal year 2008/2009 after deleting the prevalent cases from April 1991 to March 2008. To see the pattern of incidence, we have rates from 2000/01 through 2008/09, using nine years of run-in, that is, nine years was used to delete the prevalent cases. Both crude and age-standardized incidence rates for each sex were obtained after deleting prevalent cases for nine years. Finally, the annual relative change (ARC = (exp (β) – 1) × 100) was estimated from the weighted Poisson regression model for each sex.
Results:
In 2008/09 fiscal year the overall incidence of OA using Def1 was 14.6 (12.7 in men and 16.5 in women) per 1000 person years, and 8.2 (7.2 in men and 9.3 in women) per 1000 person years in Def2. Between 2000/01 and 2008/09, crude incidence rates of OA based on Def1 varied from 11.8 to 14.2 per 1000 person years in men and from 15.7 to 18.5 per 1000 person years in women and the rates were lower to about 53-55% using Def2 (Table). For the crude rates, the ARCs were 3% (p < 0.01) and 2% (p < 0.01) for men and women respectively, in Def1, and the changes were similar in Def2. The age-standardized ARCs were not significantly different from 0% in both case definitions.
Conclusion:
Our study suggests that physician diagnosed incidence of OA is higher in both men and women. Crude incidence rates of OA are increasing slightly over the years but the age-standardized rates do not show an increasing or decreasing pattern over the years. These data have implications in public health services for forecasting prevalence and costs of OA and in epidemiologic research.
Table:Crude and age-standardized incidence of osteoarthritis per 1000 person years using nine years of run-in to delete the prevalent cases.
|
|
Men Def11 |
Men Def22 |
Women Def11 |
Women Def22 |
||||
|
|
Crude |
Standardized |
Crude |
Standardized |
Crude |
Standardized |
Crude |
Standardized |
|
Year |
|
|
|
|
|
|
|
|
|
00/01 |
11.8 |
12.7 |
6.3 |
6.8 |
15.7 |
17.0 |
8.5 |
9.2 |
|
01/02 |
11.6 |
12.3 |
6.1 |
6.5 |
15.7 |
16.7 |
8.8 |
9.4 |
|
02/03 |
11.7 |
12.1 |
6.2 |
6.4 |
15.4 |
16.0 |
8.5 |
8.9 |
|
03/04 |
12.5 |
12.7 |
6.6 |
6.8 |
16.9 |
17.2 |
9.3 |
9.5 |
|
04/05 |
12.6 |
12.6 |
6.7 |
6.7 |
17.3 |
17.3 |
9.7 |
9.7 |
|
05/06 |
13.6 |
13.2 |
7.1 |
6.9 |
17.8 |
17.4 |
9.7 |
9.5 |
|
06/07 |
13.5 |
12.8 |
7.5 |
7.1 |
18.1 |
17.3 |
9.8 |
9.3 |
|
07/08 |
13.9 |
12.9 |
7.4 |
6.8 |
18.1 |
16.9 |
10.2 |
9.4 |
|
08/09 |
14.2 |
12.9 |
7.9 |
7.1 |
18.5 |
16.8 |
10.2 |
9.2 |
|
ARC* |
3% |
1% |
3% |
1% |
2% |
0% |
3% |
0% |
|
p-value |
< 0.01 |
0.43 |
< 0.01 |
0.31 |
< 0.01 |
0.71 |
< 0.01 |
0.91 |
1Def1: one visit to a health professional or one hospital diagnosis. 2Def2: two visits to a health professional in two years or one hospital diagnosis. *ARC stands for annual relative change = (exp (β) – 1) × 100 and was estimated from Poisson regression.
Disclosure:
M. M. Rahman,
None;
J. Cibere,
None;
C. H. Goldsmith,
None;
A. H. Anis,
None;
J. A. Kopec,
None.
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