Irregular breathing during sleep could lead to memory loss at later stages. The study relates low blood flow to the brain as a possible reason for memory loss and further cognitive degeneration in the long run.

Researchers found that older women aged 65 and above who suffered from disorderly breathing have an increased risk of developing mild cognitive impairment or dementia in subsequent years.

The study, published in the Journal of the American Medical Association in its August 10 issue explained breathing difficulties as a measure of hypoxia or oxygen deficiency. Overnight lack of steady oxygen flow to the brain was seen as the prime factor that linked thinking or memory patterns, as against measures that show how much total sleep a women got or how many times they woke up during the night.

The study notes, "Sleep-disordered breathing, a disorder characterized by recurrent arousals from sleep and intermittent hypoxemia, is common among older adults and affects up to 60 percent of elderly populations". A number of adverse health outcomes including hypertension, cardiovascular disease, and diabetes have been associated with sleep-disordered breathing in the past.

Kristine Yaffe, M.D., of the University of California, San Francisco, and colleagues examined the co-relation between existing sleep-disordered breathing as measured with polysomnography (monitoring of physiological activity during sleep) and subsequent diagnoses of mild cognitive impairment and dementia. This study is based on long-term data as against earlier short term data available on the same condition.

The findings note that when factors such as race, weight, and other diseases and medications were taken into account, women with sleep apnea were almost twice as likely to test positive for cognitive impairment or dementia. In the past, sleep apnea has also been linked to a host of other health problems such as high blood pressure and cholesterol.

In the new study, physician Kristine Yaffe and colleagues observed 298 women, average age 82, from 2002 to 2004 for sleep problems, monitoring each individual overnight and noting any blockage of  air flow in their breathing that caused them to wake up from their sleep.

Study co-author Katie Stone, an epidemiologist at the California Pacific Medical Centre in San Francisco explained, "About one-third of the patients had disordered breathing. "None of these women was cognitively impaired at the time of the sleep test. After the test, patients were given their scores and told if they showed signs of severe sleep problems."

She added, "When researchers repeated standard cognition tests on the women roughly five years later, 45 percent of those who had disordered breathing had developed dementia or milder cognitive impairments, compared with 31 percent of those with no breathing irregularities." She was not sure whether the subjects sought any kind of treatment during the testing phase.

Yaffe inferred that people with sleep apnea should also try to be tested occasionally for signs of cognitive decline. The study however does not clear the air on whether treating sleep apnea or its causes could actually prevent the memory loss decline which needs further investigations.

In an accompanying editorial, Nicola Canessa, Ph.D., of the Centre for Cognitive Neuroscience, and Luigi Ferini-Strambi, M.D., of the Universita Vita-Salute San Raffaele, Milan, Italy, wrote, "the study by Yaffe et al and related studies to date suggest that large trials with continuous positive air pressure (CPAP) treatment in elderly participants with sleep-disordered breathing should be performed."

Canessa added, "Moreover, in trials evaluating the effects of pharmacological and nonpharmacological (e.g., cognitive training and rehabilitation) interventions on cognitive function in patients with mild cognitive impairment or dementia, the possible coexistence of sleep-disordered breathing should be considered."

She suggested, "Finally, physicians of patients with mild cognitive impairment and sleep-disordered breathing for whom treatment with CPAP may be indicated should consider these results and future guidelines to formalize the clinical management of patients with mild cognitive impairment should consider the implications of this study and related research."