Sleep apnoea linked to dementia

Studies that look at the sleeping patterns of elderly people often indicate ‘restless’ nights are bad for the brain, and new research supports this claim.

A study of women aged 65 years of age and older found breathing irregularities that rob the brain of oxygen during sleep; also known as sleep apnoea or hypoxia, may imperil a person’s ability to think straight.

Hypoxia is a pathological condition in which a person becomes deprived of adequate oxygen supply. Individuals with disordered breathing slow down or stop taking breaths during sleep and often must “gasp to catch up”.

Researchers reported those of the women studied with seriously disordered breathing had an increased risk of developing mild cognitive impairment or dementia in later years.

Previous short-term studies have linked disordered breathing to cognitive impairment, citing hypoxia as a culprit.

In the new study, physician Kristine Yaffe, of the University of California and her colleagues, tested 298 women, with an average age of 82 years, for sleep problems from 2002 to 2004. Overnight monitoring of each individual recorded any stoppages of air flow in their breathing or and arousals from sleep.

About one-third of the patients had disordered breathing and were not cognitively impaired at the time of the sleep test. After the test, patients were given their scores and told researchers if they showed signs of severe sleep problems.

When researchers repeated standard cognition tests on the women about five years later, 4% of those who had disordered breathing had developed dementia or milder cognitive impairments.

In particular, women who had 15 or more breathing stoppages per hour, and who spent more than 7% of sleep time not breathing during the earlier part of the study were nearly twice as likely as those without breathing problems to develop dementia or other cognitive impairments.

Mark Aloia, a psychologist at National Jewish Health in Denver, said hypoxia is not good for the brain, and the study “definitely strengthens the idea that hypoxia has detrimental effects”.

Patients with obstructive sleep apnoea, the most common form of disordered breathing, can benefit from a machine, in which a mask fitted over the mouth and nose, delivers air constantly during sleep.

Since no medications are known to prevent mild cognitive impairment from progressing to dementia or Alzheimer’s disease, “treating at-risk patients for sleep-disordered breathing is a prevention strategy that may be worth testing,” the researchers suggested.