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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.