The data

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The data are from the National Longitudinal Survey of Children and Youth (NLSCY), which has been conducted every two years since 1994/1995. This report examines trends from 1994/1995 to 2008/2009 in the prevalence of upper respiratory infections and otitis media among children aged 2 to 3 years, and in the prevalence of asthma among children aged 2 to 7 years.

The information used in this analysis was provided to the NLSCY by the person most knowledgeable about the child, usually the mother. The prevalence of health conditions was based on the parent's response to the following questions:

Upper respiratory infections: How often does this child have nose or throat infections (almost all the time, often, from time to time, rarely, or never)?
Otitis media: Since birth, has this child had an ear infection (otitis)? If yes, how many times?
Asthma and asthma symptoms: Has this child ever had asthma that was diagnosed by a health professional? Has this child had an asthma attack in the past 12 months? Has this child had wheezing or whistling in the chest any time in the last 12 months? Does this child take any of the following prescribed medications on a regular basis: Ventolin, inhalers, puffers for asthma?

Income status was measured as the ratio of household income to the low-income cut-off for the size and location of the child's household.

Cross-sectional survey weights were used for the analyses. For statistical tests, the variances and standard errors of all estimates were calculated using the bootstrap weights developed by Statistics Canada for each of the cross-sectional samples.