Sleep Apnoea ups Stroke Risk

Middle-aged and older adults who suffer from the sleep disorder, obstructive sleep apnoea (OSA), may be at an increased risk of stroke, the results of a new study indicate.

According to US researchers, this increased risk is particularly noticeable in men.

Sleep apnoea is a potentially life-threatening condition in which breathing is disrupted during sleep. The most common type is OSA. According to the Irish Sleep Apnoea Trust, up to 7,000 people in Ireland have been diagnosed with OSA, however, EU research indicates that many more may actually be affected.

The condition has been linked to excessive daytime sleepiness, which lowers performance in the workplace and at school, and increases the risk of injuries and death from driving while drowsy and other accidents.

These new results were based on the latest findings from the Sleep Heart Health Study (SHHS), which is the largest and most comprehensive study on the risk of heart-related conditions linked to sleep apnoea.

In this latest report, researchers studied the stroke risk of 5,422 people, aged 40 and older. None of the participants had a history of stroke at the start of the study and all were assessed to determine if they had sleep apnoea, and if so, the severity of it.

Each was monitored for an average of nine years. During this period, 193 people had a stroke – 85 men and 108 women.

After adjusting for several heart risk factors, the researchers found that the effect of sleep apnoea on stroke risk was stronger in men than in women.

In men, even those with mild sleep apnoea were found to be at an increased risk of suffering a stroke. This risk increased as sleep apnoea severity increased, from mild levels to moderate to severe levels.

Overall, men with moderate to severe sleep apnoea were nearly three times more likely to have a stroke than men without sleep apnoea or with mild sleep apnoea.

Meanwhile in women, the increased risk of stroke was significant only in those with severe levels of sleep apnoea.

The study also found that the risk from sleep apnoea was independent of other risk factors such as weight, high blood pressure, smoking and diabetes.

Every year in Ireland, around 10,000 people suffer a stroke, while 2,500 people die as a result. Thousands more are living with stroke-related disabilities.

"Although scientists have uncovered several risk factors for stroke, such as age and high blood pressure and diabetes, there are still many cases in which the cause or contributing factors are unknown. This is the largest study to date to link sleep apnoea with an increased risk of stroke. The time is right for researchers to study whether treating sleep apnoea could prevent or delay stroke in some individuals,” the researchers said.

They suggested that the differences between men and women might be because men are more likely to develop sleep apnoea at a younger age. Therefore, they tend to have untreated sleep apnoea for longer periods of time than women.

"It's possible that the stroke risk is related to cumulative effects of sleep apnoea adversely influencing health over many years," said lead researcher, Prof Susan Redline of Case Western Reserve University in Cleveland.

She insisted that the findings provide ‘compelling evidence that obstructive sleep apnoea is a risk factor for stroke, especially in men’.

"Overall, the increased risk of stroke in men with sleep apnoea is comparable to adding 10 years to a man's age. Importantly, we found that increased stroke risk in men occurs even with relatively mild levels of sleep apnoea,” she said.

Details of these findings are published in the American Journal of Respiratory and Critical Care Medicine.