Medical Matters: For those of us who do not suffer from asthma, there is understandably a perception that winter is the worst season for the disease. The many viruses and bacteria that circulate during the winter months certainly trigger acute symptoms in the vulnerable patient with asthma.
But the summer months can be troublesome also. Many patients with asthma are also prone to hayfever, reflecting the common allergic pathway shared by both disease processes. A high pollen count may cause wheezing as well as the streaming eyes and nose of hayfever.
Our recent weather conditions can also be bothersome. The heavy, humid and overcast day is one that certain people with asthma do not look forward to. The airless conditions combined with an "inverted" type of atmospheric weather pattern can push an otherwise stable patient into acute wheezing and breathlessness.
There was some interesting research into asthma presented at a recent conference of the American Thoracic Society (ATS). A study of 235 patients at the New York Medical Centre found that more than half developed asthma symptoms in response to laughter.
Prof Stuart Garay said he was surprised to discover how common a trigger factor laughter was. "It's as common as some of the most well-known asthma triggers, such as grasses, pollen and fumes, and it's even more common than dust mites, allergy to animals and moulds. It's a little-appreciated trigger factor."
Nor, I'm sure, is it appreciated by asthma patients. We all enjoy a good laugh. At least the study found that laughter-induced asthma was not so severe as to require emergency treatment or hospitalisation. The most common symptom in patients with laughter-induced asthma was coughing followed by chest tightness.
As to how laughter actually triggers asthma symptoms, no one is certain, although the US researchers feel it could be linked to hyperventilation. And for those whose asthma is well controlled, there was good news: they can laugh longer and harder before getting a symptom flare-up.
University of Michigan respiratory specialists told the ATS meeting of a link between breathing problems during sleep and asthma. The study of 115 people with moderate to severe asthma found that 33 per cent of men and 49 per cent of women had obstructive sleep apnoea, a condition in which people stop breathing for periods during sleep.
Dr William F Bria II, associate professor of internal medicine at the University of Michigan medical school, said the findings suggested that doctors should examine their asthma patients' sleep patterns, especially if patients continued to have symptoms despite good compliance with treatment. "The more you look for sleep apnoea with patients with asthma, the more you find it," he said.
One of the giveaways that might help alert patients and their doctors is the occurrence of excessive daytime sleepiness. Some 55 per cent of those studied complained of being less alert during the day, which doctors had been blaming on the asthma itself.
But this study points to a link between sleepiness and apnoea symptoms rather than a link with asthma severity. So if you have asthma and you snore a lot, you might mention it to your family doctor or asthma specialist.
Meanwhile, there was a good reaction to my request in last week's column for feedback on readers' experience of respiratory infection after flying. Judging by your responses, some otherwise healthy people are prone to developing an infection just after they return home. Nor does the length of the flight seem to matter; your experiences suggest short-haul and long-haul journeys precipitate the problem.
But before running off to buy surgical masks in advance of your next flight, it is important to reiterate there is, as yet, no scientific evidence to link this occurrence with the constant recirculation of air on board modern aircraft.
Finally, on the topic of deep vein thrombosis (DVT) and flying, my attention has been drawn to a recent National Medicines Information Centre bulletin which says there is no proven benefit in otherwise healthy people taking aspirin before a long-haul journey. But the guidelines are interim ones and if you have a condition that places you at greater risk of thrombosis as outlined last week, then a visit to your doctor is advised. He may offer you anti-coagulant treatment before you fly.
Dr Muiris Houston is pleased to hear from readers at mhouston@irish-times.ie but regrets he cannot answer individual queries.
