Asthma is one of the most common respiratory diseases in the world today. The Global Initiative for Asthma (GINA) claimed in 2010 that more than 300 million people are affected by asthma worldwide.
It affects one in ten children (10%) and one in twenty adults (5%). It occurs for the first time at any age, even in adulthood, although it usually begins before the age of five.
Roughly 80% of all childhood asthma occurs before the age of five.
It’s more common in boys and is seen predominantly in children who are allergic or come from allergic families. It tends to run in families, as do related allergic conditions, such as hay fever and eczema.
Approximately 50% of childhood asthma, particularly if it’s mild, goes into remission during the teenage years, but don’t be fooled into thinking this means you have "outgrown" asthma. As many as 30% of “teenagers-in-asthma-remission” go on to re-develop asthma during adulthood. Asthma usually persists if contracted during adulthood.
For decades it was accepted that allergic diseases were infrequent among black people and in people who live in rural communities.
This may be because living in the country protects people from developing asthma, even if they have the genetic potential to be asthma sufferers. Recent studies have confirmed that black people with asthma are much less likely to have parents or older siblings who suffer from asthma (positive family history) than other asthma sufferers.
However, if a black person does have a positive family history of asthma, they are much more likely to have asthma than black people without a family history, and even people from other races with a family history! In patients who have moved from rural to urban areas, either the early exposure to foreign allergens from the newly adopted western lifestyle or the loss of protection from the rural lifestyle, contributes to a higher degree of allergic sensitisation recorded among African infants than in other races. These factors account for the increased number of black children who have asthma.
Exposure to urban living
Studies conducted on people living in rural areas in Transkei have shown that migration to urban and peri-urban settlements has resulted in a 20-times increased risk of developing asthma symptoms. The incidence of asthma in rural areas has also increased.
What are the mechanisms of asthma?
Reviewed and updated by Prof Eugene Weinberg, Paediatrician Health24, April 2015.