Characteristics of the study cohort according to neighborhood socioeconomic status, N = 100,566.

Note: The p-value statistic for heterogeneity across categories was *Neighborhood socioeconomic status was measured by the percentage of households in the census-tract level below the 1999 federal poverty levels based on 2000 US census. Quartile 1 corresponds to the lowest socioeconomic (highest household poverty rates) group and Quartile 4 corresponds to the census tracts with the highest socioeconomic status relative to others in the study.