According to a new study, lack of sleep can promote atrophy (shrinkage) of the brain and cognitive decline. The brain is responsible for cognitive abilities; therefore, faster shrinkage of the brain is associated with decline in cognitive performance. The study was published on July 1 in the journal SLEEP by researchers at the Center for Cognitive Neuroscience, Neuroscience and Behavioral Disorders Program, Duke-NUS Graduate Medical School, Singapore.
The objective of the study was to examine the impact of sleep duration and quality to age-related changes in brain structure and cognitive performance among relatively healthy older adults. The study group comprised 66 relatively healthy adults aged 55 years or older (average age: 67 years) at the beginning of the study. The seniors underwent magnetic resonance imaging (MRI) and neuropsychological assessment every two years. Self-reported sleep duration was recorded and blood samples for high-sensitivity C-reactive protein were drawn. (C-reactive protein is a marker for systemic inflammation.).
The average reported time in bed was 6.7 hours; shorter sleep was defined as one hour less than the average. However, the study authors estimated that the subjects’ actual sleep time was probably about six hours because sleep efficiency decreases with age. The investigators found that each hour of reduced sleep duration noted at the study onset increased the annual expansion rate of the ventricles (brain cavities) by 0.59% and an annual decline rate in overall cognitive performance by 0.67% in the subsequent two years. The data was controlled for the effects of age, gender, education, and body mass index (BMI). In contrast, overall sleep quality reported at the study onset did not impact either brain or cognitive aging. High-sensitivity C-reactive protein did not correlate with baseline sleep duration, brain structure, or cognitive performance.
The authors concluded that among healthy seniors, short sleep duration was associated with increased age-related brain atrophy and cognitive decline. However, these associations were not associated with elevated inflammatory responses among short-duration sleepers. Because sleep duration is less controllable as one ages, the researchers are of the opinion that the study is particularly important for young people; this is because younger individuals may be more able to improve their sleep time. The investigators plan to continue to follow the group of seniors for four to six more years; they expect the relationship between brain shrinkage and less sleep to continue as they. They explain that the measured declines in cognition and brain shrinkage appeared to be small; however, accumulated over decades, they may become more significant.