As previously featured in aging in action, there is some evidence that sleep-disordered breathing (SDB) may contribute to cognitive impairment among older adults. If this is the case, treatment of SDB may be an effective way to prevent cognitive decline for many. A review in Current Neurology and Neuroscience Reports summarizes the existing research in this area, and presents a hypothetical model of how SDB may contribute to cognitive impairment.
One significant finding in the literature is that obstructive sleep apnea (OSA) and SDB are increasing in prevalence in the older adult population, the cause of which is unknown. Older adults with dementia appear to have a greater rate of sleep disorders than the general older adult population, though it is unclear whether one condition causes the other, or whether both share an underlying cause.
There seem to be a few plausible relationships between SDB and cognitive decline. It has been hypothesized that the oxygen deficit that can occur from OSA may explain some of the apparent relationship between SDB and cognitive impairment, though findings on the relationship between OSA and cognitive decline have been mixed. Some research suggests that younger adults with OSA are more vulnerable to suffering cognitive effects than are older adults with OSA, while some suggests that OSA may explain some cognitive impairment in older adults. Some researchers believe that it is through fragmentation and disruption of sleep that SDB can cause cognitive impairment, rather than through disrupted intake of oxygen, although the authors argue that the lack of oxygen has stronger evidence in the existing research. It has also been hypothesized that individuals with mild cognitive impairment (MCI) are more vulnerable to the effects of SDB than the general population.
The authors propose a model in which the lack of oxygen caused by OSA damages the vascular health of the individual, which can negatively impact the subject’s cognitive health through multiple pathways. The authors suggest that longitudinal studies be conducted to test the various hypotheses that have been suggested by the associations between SDB and cognitive decline, and to resolve the competing hypotheses on whether or not SDB affects cognition across age groups.
Zimmerman ME, Aloia MS. Sleep-disordered breathing and cognition in older adults. Current Neurology and Neuroscience Reports; (2012). 12: 537-546.