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Table 3 Distribution of 10,394 cases of schizophrenia, incidence of schizophrenia, and adjusted relative risks according to the geographical distance to nearest major road at the 15th birthday and the degree of urbanization at the 15th birthday.

From: Urbanization and traffic related exposures as risk factors for Schizophrenia

Variable No. of cases Incidence * Relative Risk (95 percent Confidence Interval)
    First Adjustment † Second Adjustment ‡
Total 10,394 3.31 - -
Geographical distance to nearest major road at the 15th birthday     
   0–50 m 1,089 3.08 1.16 (1.04, 1.30) 1.05 (0.94, 1.18)
   50–100 m 846 3.37 1.25 (1.11, 1.40) 1.08 (0.96, 1.21)
   100–250 m 2,308 3.38 1.25 (1.13, 1.38) 1.07 (0.96, 1.18)
   250–500 m 2,560 3.47 1.27 (1.15, 1.40) 1.05 (0.94, 1.16)
   500–1000 m 2,187 3.52 1.30 (1.17, 1.44) 1.06 (0.96, 1.18)
   1000–2000 m 961 2.95 1.13 (1.01, 1.27) 1.02 (0.91, 1.14)
   >2000 m 443 2.57 1.00(ref) 1.00 (ref)
    (p < .00001) (p = 0.77)
Degree of Urbanization at the 15th birthday     
   Capital 1559 6.53 2.10 (1.98, 2.24) 2.09 (1.96, 2.22)
   Capital Suburb 1947 4.07 1.48 (1.40, 1.56) 1.47 (1.38, 1.56)
   Provincial City 1154 3.49 1.34 (1.25, 1.43) 1.32 (1.23, 1.42)
   Provincial Town 2670 2.96 1.13 (1.07, 1.19) 1.12 (1.06, 1.18)
   Rural Area 3064 2.56 1.00 (ref) 1.00 (ref)
    (p < .00001) (p < .00001)
  1. *: Incidence of schizophrenia per 10,000 person years at risk. The incidence measures the number of new cases occurred per time period
  2. † Estimates of relative risks were adjusted for age and its interaction with gender, calendar year of diagnosis, and mental illness in a parent or sibling.
  3. ‡ Estimates of relative risk were adjusted for all variables in the first adjustment and for all the variables listed.