Study: Changes in the prevalence of asthma among Canadian children

View the most recent version.

Asthma, one of the most common chronic conditions in childhood, afflicted more and more children during the late 1990s, but actual asthma attacks became less common, according to a new study.

In 1994/1995, about 11% of children aged 11 and under, or nearly 520,000, had been diagnosed with asthma. By 2000/2001, the rate had risen to more than 13%, an increase of nearly 70,000 children.

The study, "Changes in the prevalence of asthma among Canadian children," published today in Health Reports, showed that the increase was statistically significant only for children aged 5 or younger, and for those aged 10 and 11.

On the other hand, the prevalence of asthma attacks declined during this period. In 1994/1995, just over half of children with asthma were reported to have had an attack in the previous year; by 2000/2001, this proportion had dropped to 39%.

The data, which came from the National Longitudinal Survey of Children and Youth, also showed that the proportion of children with high-severity asthma symptoms also declined during this period.

Among children with asthma, the proportion with high-severity symptoms dropped from 41% in 1994/1995 to 36% in 2000/2001.

The likelihood of having had an asthma attack depended on the severity of the disease. For example, in 2000/2001, 70% of children with high-severity asthma were reported to have had an attack in the past year, compared with fewer than 10% of those with low-severity asthma.

Boys more likely to be diagnosed with asthma

Boys were significantly more likely than girls to have been diagnosed with asthma. In 2000/2001, 16% of boys were reported to have asthma, compared with around 11% of girls.

The prevalence of asthma among boys rose significantly, from just under 14% in 1994/1995 to 16% in 2000/2001. However, the percentage of boys with asthma who had had an attack in the past year fell from 52% to 41%. Girls also saw an increase in prevalence from around 8% to more than 10%, and a decrease in past-year attacks among those who had asthma from close to 50% to 37%.

Asthma rates highest in Atlantic provinces

Childhood asthma rates in Canada differed by region, with the highest rates in the four Atlantic provinces: Nova Scotia, Newfoundland and Labrador, New Brunswick and Prince Edward Island.

Other research has shown that even when environmental conditions such as ozone, temperature, and relative humidity were taken into account, children in the Atlantic provinces continued to show higher rates of asthma.

Children in British Columbia and the three Prairie provinces had the lowest asthma rates.

Risk of asthma higher among children in smoking households

Children living in households where either parent was a daily smoker were significantly more likely than children in non-smoking households to have been diagnosed with asthma or to have asthma-like symptoms.

Childhood asthma not related to income or urban/rural residence

While low income generally tends to be associated with poor health, and high income with good health, the relationship between household income and childhood asthma did not follow this pattern.

In 2000/2001, the prevalence of childhood asthma did not differ significantly by household income. Similarly, among those with asthma, the likelihood of having had an attack in the past year was not related to household income.

As well, the prevalence of asthma did not differ significantly between children living in rural areas compared with those in urban areas.

Definitions, data sources and methods: survey number 4450.

The article, "Changes in the prevalence of asthma among Canadian children," which is part of today's Health Reports, Vol. 19, no. 2 (82-003-XWE, free) online release, is now available from the Publications module of our website.

For more information, or to enquire about the concepts, methods or data quality of this release, contact Rochelle Garner (613-951-3977; rochelle.garner@statcan.gc.ca) or Dafna Kohen (613-951-3346; dafna.kohen@statcan.gc.ca), Health Information and Research Division.

For more information about Health Reports, contact Christine Wright (613-951-1765; christine.wright@statcan.gc.ca), Health Information and Research Division.