PURPOSE: To examine the age, period, and cohort effects on asthma prevalence among Canadian adults from 1994/1995 to 2010/2011.

METHODS: Using data from the National Population Health Survey, 13,616 Canadian adults were followed for 16 years. Age was limited to 18-80 years during follow-up. Modified Poisson regression models with generalized estimating equations were used to estimate age, period, and cohort effects on asthma and active asthma prevalence after accounting for sociodemographic factors. Model-based standardization was performed to estimate standardized rates.

RESULTS: Overall asthma prevalence increased from 5% in 1994/1995 to 11% in 2010/2011; decreasing from 12% for 20-year-olds to 6% for 50-60-year-olds and then increased to 8% for 80-year-olds. Individuals aged 20 years had the steepest increase in prevalence between 1994/1995 and 2010/2011. Active asthma prevalence increased from 5% in 1994/1995 to 8% in 2010/2011; decreasing from 8% for 20-year-olds to 5% for 50-60-year-olds and then increased to 6% for 80-year-olds.

CONCLUSIONS: Our findings suggest the presence of age, period, and cohort effects on prevalence of asthma overall and presence of age and period effects on active asthma prevalence in Canadian adults.