There are several risk factors associated with obstructive sleep apnea that are long-standing and well-known. They include lifestyle and health factors such as obesity or excess body weight, high-blood pressure, and alcohol and tobacco use, as well as genetic and demographic factors such as family history of the disease, being older, and being male. Now, thanks to new research, we may have a new OSA risk factor to add to this list: asthma.Researchers at the University of Wisconsin investigated the influence of asthma in the development of obstructive sleep apnea. They found a significantly elevated risk for OSA among people with asthma. Those people who'd developed asthma as children were at particularly elevated risk. Researchers observed 773 adult men and women over a period of eight years. All were participants in the Wisconsin Sleep Cohort study, and were between ages 30-60 at the time the study began. Of the 773 participants, 201 had asthma at the beginning of the study period, and 61 of them had developed asthma during childhood. None of the participants had obstructive sleep apnea. Every four years, the subjects participated in laboratory sleep evaluations, clinical health assessments, and health questionnaires. After adjusting for other risk factors for sleep apnea, including age, gender, body-mass index, smoking, and nasal congestion, researchers found that the presence of asthma significantly increased the risk for sleep apnea:
- People with asthma were 1.70 times more likely to develop sleep apnea over the eight-year study period than those without asthma.
- Among those in the study who had developed asthma during childhood, the risk was even higher. These people had 2.34 times the risk of developing obstructive sleep apnea, compared to those without asthma.
- Researchers found that the longer asthma had been present, the higher the risk for sleep apnea. Every five-year period a person had asthma was associated with a 10 percent increase to their risk of developing obstructive sleep apnea.
- Among the participants, 45 developed asthma during the study observation period. Researchers found that these people were 48 percent more likely to develop sleep apnea than those without asthma. The size of this group was too small for researchers to demonstrate a statistical significance to these results. In their discussion of the study's results, researchers pointed to this particular finding as an important one for follow-up investigation.
- In a study of more than 4,500 adults ages 20-69, asthma was found associated with symptoms common to sleep apnea, including snoring, apneas, and daytime sleepiness.
- Researchers at Israel's Technion-Israel Institute of Technology investigated whether difficult-to-control asthma might influence the onset of sleep apnea. They found that patients with unstable, hard-to-control asthma were at significantly higher risk for obstructive sleep apnea.
- Researchers at the University of Wisconsin also looked at the risk of sleep apnea among patients with poorly controlled asthma, and found these patients were at higher risk for obstructive sleep apnea after adjusting for other sleep apnea risk factors, including obesity.
These and other previous studies have identified an association between the two disorders, asthma and sleep apnea. The latest study comes an important step closer to establishing a causal link between the two conditions, by examining specifically the direction of the relationship between the two. The presence of asthma in people later identified as being more likely to develop sleep apnea suggests that asthma may actually contribute to the onset of sleep apnea.
Asthma is a lung disease that causes difficulty breathing, shortness of breath, coughing, and wheezing. Some people can experience these symptoms at night, and they can interfere with sleep. Establishing asthma as a risk factor for OSA is an important public health development. More than 25 million Americans suffer from asthma, including seven million children. If these adults and children are at higher risk for obstructive sleep apnea because of their asthma, they are also at risk for the complications that come with sleep apnea. Obstructive sleep apnea is associated with increased risk for a number of health problems, including heart disease, diabetes, and some cancers. Children can experience apnea and sleep-disordered breathing as well, and children have their own set of health risks associated with the condition, including problems with emotional, social, and cognitive development.
Finding new ways to identify and prevent obstructive sleep apnea is critical to the sleep and overall health of millions of Americans who suffer from this serious sleep disorder. The research into the role of asthma is an important step in this direction.
Michael J. Breus, PhD
The Sleep Doctor®
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