TABLE 1.
NUMBER OF PERSON-YEARS OF FOLLOW-UP AND TOTAL DEATHS IN SIX CITIES: PERIOD 1 (1974–1989 FOLLOW-UP) AND PERIOD 2 (1990–1998 FOLLOW-UP)
| Characteristics | Portage | Topeka | Watertown | Harriman | St. Louis | Steubenville | ||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| No. participants | 1,630 | 1,238 | 1,332 | 1,258 | 1,292 | 1,346 | ||||||
| Period 1* (1,364 deaths; 104,243 person-yr) | ||||||||||||
| Person-yr | 20,224 | 14,967 | 18,640 | 16,991 | 16,572 | 16,849 | ||||||
| No. deaths | 212 | 149 | 238 | 219 | 267 | 279 | ||||||
| Deaths/1,000 person-yr | 10.5 | 10.0 | 12.8 | 12.9 | 16.1 | 16.6 | ||||||
| Average PM2.5 (μg/m3) | 11.4 | 12.4 | 15.4 | 20.9 | 19.2 | 29.0 | ||||||
| Period 2 (1,368 deaths; 54,735 person-yr) | ||||||||||||
| Person-yr | 11,658 | 9,062 | 8,979 | 8,363 | 8,172 | 8,501 | ||||||
| No. deaths | 264 | 184 | 194 | 229 | 251 | 246 | ||||||
| Deaths/1,000 person-yr | 22.6 | 20.3 | 21.6 | 27.4 | 30.7 | 28.9 | ||||||
| Average PM2.5, μg/m3 | 10.2 | 13.1 | 12.1 | 18.1 | 13.4 | 22.0 | ||||||
*
Period 1 is restricted to 1,974 through 1989, whereas the original Dockery and colleagues (7) analysis included person-years of follow-up through June 1991 for a total of 111,076 person-years and 1,430 deaths. In Period 1, average PM2.5 (μg/m3) is the mean concentration in 1980–1985, the years when there are monitoring data for all cities (18). In Period 2, average PM2.5 is the mean concentrations of the estimated PM2.5 in 1990–1998.