Table 1.
Cohort Designs Used to Obtain Study Populations Without Medicare Claims for Coronary Heart Disease, REGARDS Study, 1999–2007
| Look-Back Period | Amount of Medicare Coverage Required at Study Entrya | No. of Participants With Required Coverage | Duration of Time Used to Determine the Presence of CHD Claimsa,b | No. of Participants Without CHD Claimsb |
|---|---|---|---|---|
| 6-month fixed-window | ≥6 months before index date | 8,937 | 6 months before index date | 8,603 |
| ≥6-month all-available | ≥6 months before index date | 8,937 | Maximum continuous coverage before index date | 7,682 |
| 1-year fixed-window | ≥1 year before index date | 8,483 | 1 year before index date | 7,908 |
| ≥1-year all-available | ≥1 year before index date | 8,483 | Maximum continuous coverage before index date | 7,255 |
| 2-year fixed-window | ≥2 years before index date | 7,556 | 2 years before index date | 6,756 |
| ≥2-year all-available | ≥2 years before index date | 7,556 | Maximum continuous coverage before index date | 6,411 |
Abbreviations: CHD, coronary heart disease; ICD-9, International Classification of Diseases, Ninth Revision; REGARDS, Reasons for Geographic and Racial Differences in Stroke.
a For the current study, the REGARDS in-home visit was used as the index date.
b CHD claims included those containing ICD-9 codes for myocardial infarction or ICD-9 and Current Procedural Terminology codes for coronary revascularization (see text for details).