A new study (in Sleep) reveals a link between poor sleep quality and the development of cognitive decline in men over three to four years. Higher levels of fragmented sleep and lower sleep efficiency were associated with a 40 to 50 per cent increase in the odds of a clinically significant decline in executive function (responsible for planning, making decisions, correcting errors, troubleshooting, and abstract thinking). The decline seen was similar in magnitude to the effect of a five-year increase in age – but sleep duration was not related to cognitive decline. The mechanisms that link poor sleep to mental decline aren’t known, and further research is needed to determine if this association remains after a longer follow-up period. Poor sleep has been linked to cardiovascular issues that have been implicated in cognitive impairment and Alzheimer’s disease, however, so consult your doctor if your (or your spouse’s) sleep is fragmented.