Cause-specific mortality by income adequacy in Canada: A 16-year follow-up study.

Background: People with lower incomes tend to have less favourable health outcomes than do people with higher incomes. Because death registrations in Canada do not contain information about the income of the deceased, vital statistics cannot be used to examine mortality by income at the individual level. However, through record linkage, information on the individual or family income of people followed for mortality can be obtained. Recently, a large, population-based sample of Canadian adults was linked to almost 16 years of mortality data.

Methods: This study examines cause-specific mortality rates by income adequacy among Canadian adults. It is based on data from the 1991 to 2006 Canadian census mortality and cancer follow-up study, which followed 2.7 million people aged 25 or older at baseline, 426,979 of whom died during the 16-year period. Age-standardized mortality rates (ASMRs), rate ratios, rate differences and excess mortality were calculated by income adequacy quintile for various causes of death.

Results: For most causes examined, ASMRs were clearly graded by income: highest among people in the in the lowest income quintile, and lowest among people in the highest income quintile. Inter-quintile rate ratios (quintile 1/quintile 5) were greater than 2.00 for HIV/AIDS, diabetes mellitus, suicide, cancer of the cervix, and causes of death closely associated with smoking and alcohol.

Interpretation: These individually based results provide cause-specific information by income adequacy quintile that was not previously available for Canada.