Why is childhood asthma on the rise?
With one in five Irish children affected by the disease, should we be getting worried, asks FIONA REDDAN
IRELAND HAS the fourth highest prevalence of asthma in children in the world and one in five Irish children will now develop the illness. But what’s behind the rise?
“The short answer is that no one knows for sure, but there are plenty of theories,” says Dr Peter Greally, consultant respiratory paediatrician based in the National Children’s Hospital, Tallaght and Our Lady’s Hospital for Sick Children, Crumlin.
Dr Basil Elnazir, medical chairman of the Asthma Society of Ireland and paediatric respiratory consultant at Tallaght hospital and clinical senior lecturer at Trinity College Dublin, agrees.
“The right answer to this is we don’t know; it’s a very complicated issue,” he says.
One of the most common theories put forward is the “hygiene hypothesis”, whereby in the developed world, children’s immune systems don’t have enough to do fending off parasitic infections, so part of it turns on itself. In underdeveloped parts of the world, asthma and allergies are far less common.
Indeed, Greally points to data linking a country’s GDP with the prevalence of asthma.
“In general terms, poorer underdeveloped countries have lower rates of asthma,” he notes, adding, “It’s certainly an attractive theory, and it does explain a part of it, but there are always exceptions to any theory.
“Genetics play a significant role, but there hasn’t been a significant change in the genetic pool to account for this sharp increase [in asthma],” Elnazir notes, adding that it could be down to the interaction between genetics and the environment.
“Genetics load the gun, but the environment pulls the trigger,” he says.
What is clear is that asthma runs in families. Maternal history of asthma is typically a strong predictor in a child, while if both parents have an atopic condition (asthma, eczema, nasal conditions or allergies), then the risk of the child developing asthma is about 80 per cent.
On the other hand, if neither parent has such a condition, then the child’s risk of developing asthma is just 14 per cent.
However, while asthma might be at elevated levels, if one in five children displays symptoms of asthma, the majority will nonetheless have a mild version. “Only a minority of patients have it very, very severe. We grade asthma according to how much medication is required to control the condition,” Greally says.
In order to treat asthma effectively, it can be important to identify the trigger, which can include viral infections, exposure to dust mites or pollen, and a change in the weather.
Like most diseases, asthma comes in many shapes and forms. Younger children, particularly pre-school, get asthma-type symptoms in conjunction with a viral infection.
The most common form of asthma however is allergy-based asthma, whereby children have an allergy to house dust mites.
“A dust mite allergy is the most common one we find, and avoidance of dust mites is a very common recommendation,” says Greally. This means using a special type of fabric for pillows, keeping the child’s bedroom at a low humidity, and as dust free as possible.
A change in temperature is another trigger. In a trend that is reproducible every year, about two weeks into the new school year there will be an upsurge in the number of asthma incidents.
According to Greally, this is due to the re-emergence of the cold virus in the community. “People with asthma are very sensitive to the cold virus, and this can be an important trigger,” he says.
But the good news for many parents is that most children will grow out of it. “The best guidance we have, based on international studies, is that 60-70 per cent will outgrow it,” says Elnazir.
“Those with a good prognosis are male, have generally milder asthma that doesn’t require hospitalisation, and need less treatment to control it,” Greally adds, noting that while more boys are diagnosed with asthma than girls in childhood, more boys also tend to grow out if it, meaning that the gender balance reverses in adulthood.
Given that asthma can’t be prevented, controlling it is important, and in this regard, it is important that parents understand the myths that surround asthma.
For example, many parents of children with asthma may have been advised to stay away from dairy products such as milk but, according to Greally, there is no medical reason to do so, describing it as an “urban myth”.
“Many parents come to me asking if excluding milk could improve asthma. But there’s no basis for that in terms of the science behind asthma and it’s highly unusual for a clinician to recommend an exclusion diet to treat asthma,” he says.
Another myth is that there is a simple test for asthma. “We don’t have one test for asthma. What we have is a constellation of symptoms and clinical examination and investigations,” says Elnazir, adding that another misconception, which frequently comes up, is that taking an inhaler makes you dependent on it.
“Inhalers do not cause any dependency,” he advises.
And early in the new school year, it might be time to reflect on your child’s illness.
“The message for parents is that if your child is having regular symptoms, such as coughing on exertion or night coughing, has a diagnosis of asthma and is using a lot of relieving inhaler, then you really need to get the condition under control,” Greally says.
As Elnazir says, you want to be able to say, “I have asthma but asthma doesn’t have me.”
CASE STUDY: MOTHER AND DAUGHTER
As an asthma sufferer herself, Sarah Kelly Prior is used to relying on inhalers but the diagnosis of her daughter Rebecca with asthma tendencies at just four months of age still came as a shock.
“I was surprised that I had to give her inhalers, as I thought she was very young and I was quite shocked by it,” she recalls. Using an inhaler also proved to be difficult.
“I had to get a special one and couldn’t find it anywhere,” she says, of the special spacer devices used with small children, adding that she found one through the Asthma Society.
And, given that many asthma medications contain steroids, Sarah was also worried about giving it to such a small baby.
“I was very concerned about that, that it would impact on her and she would have terrible asthma all through her life,” she says.
However, while Sarah wasn’t diagnosed with asthma until she was five and didn’t start taking inhalers until she was aged 10, it is now recommended that early intervention improves the long-term prospects.
Sarah is a regular user of the Asthma Society’s helpline, and finds it useful to be able to talk to a nurse about Rebecca’s health, particularly given that childhood asthma can be so different to that experienced by an adult.
After a recent incident, for example, she was surprised to be advised to bring Rebecca to the hospital.
“When I’m having breathing problems myself, I wouldn’t usually go to the hospital. But when I brought Rebecca up, her oxygen levels were actually quite low,” she says.
While Sarah hopes that Rebecca may yet grow out of asthma – as so many children do – she knows from her own experiences that it won’t limit her daughter in any way.
“If you treat it properly, it shouldn’t impact on you,” she says.
“While asthma might be at elevated levels, if one in five children displays symptoms of asthma, the majority will nonetheless have a mild version . . . and based on international studies, 60-70 per cent will outgrow it