Table 1.

Summary of two main data sources

Ontario Trauma Registry "Minimum Data Sets"
Time periods	• Apr 1993 - March 1994 (n = 12,922)
	• Apr 2001- March 2002 (n = 10,782)
Criteria for inclusion	• Age at time of accident > 15 years
	• Acute hospital admission with ICD9 diagnosis codes 850-854 indicating traumatic brain injury
Variables	• Age at time of accident by 5 year cohort
	• Gender
	• Mechanism of injury (Motor vehicles, Falls, Other)
	• Geographic location (MOH Residence Code 1993 and 2001; usually corresponds to municipality; based on address of patient recorded by the Ontario Health Insurance Plan)
Statistics Canada Census Geographic files
Time periods	• 1991 Census
	• 2001 Census
Geographic location:	• 1991: 951 CSDs
Census subdivision (CSD) - usually corresponds to municipality	• 2001: 586 CSDs (reduction due to municipal amalgamation)
Variables*	• Population counts
	• Age and gender by 5-year cohorts
	• Socio-economic indicators (including Occupation, Income and Education related indicators)

* data missing or suppressed for some CSDs