Table 1.
Summary of the Number of Events and Covariate Terms Included when Adjusting for Potential Confounding, by Analytic Strategy
| New Jersey | Pennsylvania | |
|---|---|---|
| Timeframe | ||
| new users identified | April 1, 2000 June 30, 2003 | April 1, 2000 June 30, 2005 |
| covariates identified | April 1, 1999 June 30, 2003 | April 1, 1999 June 30, 2005 |
| outcomes identified | April 2, 2000 December 31, 2003 | April 2, 2000 December 31, 2005 |
| Number of events (nonvertebral fractures within 12 months) | N = 415 | N = 636 |
| Alendronate,* n=182 | Alendronate,* n=266 | |
| Risedronate, n=64 | Risedronate, n=119 | |
| Calcitonin, n=123 | Calcitonin, n=186 | |
| Raloxifene, n=46 | Raloxifene, n=65 | |
| Number of covariates in conventional model | ||
| • age dummies (31) | ||
| • month/year dummies (38)† | ||
| • other dummies (7) | 116 | |
| • other dichotomous (37) | ||
| • exposure (3) | ||
| Number of covariates in creating exposure propensity score (EPS)*** | ||
| • age dummies (31) | ||
| • month/year dummies (38 New Jersey, 62 Pennsylvania) | 113 | 137 |
| • other dummies (7) | ||
| • other dichotomous (37) | ||
| Number of covariates in creating disease risk score (DRS)*** | ||
| 1. full cohort (EPS + exposure) | 116 (full cohort) | 140 (full cohort) |
| 2. unexposed* only (same as EPS) | 113 (unexposed only) | 137 (unexposed only) |
*
Alendronate = “unexposed”
†
Due to differences in timeframe available for analysis between states, rather than including a separate covariate for each month and year during the non-overlapping time period in the conventional analysis (when July 2003 to June 2005 are only applicable for recipients from Pennsylvania), we grouped treatment initiation dates June 2003 to June 2005 as a single referent.
‡
We created state-specific EPS and DRS