Figure 2

Incidence rates of progressive encephalopathy. The incidence rates during the last 10 years of the observation period are shown. Before 1994, the incidence rates were overestimated due to artificially low numbers of person years. The incidence rates for 2003 and 2004 may be underestimated due to short observation time. However, a time trend analysis using incidence rate ratios did not demonstrate any trend changes (data shown in Table 2). During the most representative period, 1999 to 2002, the mean incidence rate was 6.13 per 100,000 person years (horizontal line).