Identifying and describing a cohort effect in the national database of reported cases of hepatitis C virus infection in Canada (1991-2010): an age-period-cohort analysis.

BACKGROUND

Hepatitis C virus (HCV) infection has a high likelihood of becoming chronic and lead to a range of conditions with poor health outcomes. Identifying birth groups highly affected by HCV infection may better focus public health interventions and ensure their cost-effectiveness. Our analysis focused on studying the association of the birth year and reporting period with rates of cases of HCV infection reported in Canada over a 20-year period.

METHODS

Laboratory-confirmed acute or chronic HCV cases with information on sex, age and year of report from 6 provinces and territories that reported line-listed data to the Canadian Notifiable Diseases Surveillance System from 1991 to 2010 were used. Sex-specific infection rates for 5-year birth groups born between 1921 and 1990 were calculated. Rates of HCV infection were log-logit transformed and underwent mean polish analysis and panel linear regression. Rate ratios of HCV infection in the 5-year age groups and their 95% confidence intervals were calculated, with rates in males and females born in 1941-1945 used as references.

RESULTS

Males born between 1946 and 1970 had 21%-40% higher reported rates of HCV infection, whereas females born between 1946 and 1975 had 12%-43% higher reported rates compared with rates in the respective sexes who were born in 1941-1945.

INTERPRETATION

Individuals born between 1946 and 1965 contributed the most to the rates of HCV infection reported in Canada between 1991 and 2010. The cohort effect was present in male and female cases of HCV infection with birth year up to 1970 and 1975, respectively. Our findings will support the development of HCV prevention programs and policies in Canada.