Short sleep during midlife ups dementia risk in old age

Persistently short sleep during midlife appears to exacerbate the risk of dementia in old age, a recent study has found.

A total of 7,959 adults (mean age 50.6±2.5 years) participated in the study and had available sleep data for analysis. Over a mean follow-up of 24.6±7.0 years, 521 participants developed dementia. Most cases of dementia were diagnosed after 70 years, with a mean age at diagnosis of 77.1±5.6 years.

At age 50, 60, and 70, a normal sleep duration of 7 hours per night consistently correlated with the lowest risk of having dementia in late life. For instance, fully adjusted Cox regression analysis found that 50-year-olds with ≤6 hours (hazard ratio [HR], 1.22, 95 percent confidence interval [CI], 1.01–1.48; p=0.04) and ≥8 hours (HR, 1.25, 95 percent CI, 0.98–1.60; p=0.07) of nightly sleep were more than 20 percent more likely to develop late-onset dementia.

At 60 years of age, short sleep was also significantly associated with late-life dementia (OR, 1.37, 95 percent CI, 1.10–1.72; p=0.005), while longer sleep was not (OR, 1.15, 95 percent CI, 0.87–1.52; p=0.34). Assessments at age 70 years showed that short (p=0.10) and long (p=0.60) nightly sleep durations were only marginally associated with an increased risk of dementia.

“Measurement of sleep duration at age 50, 60, and 70 years along with change in sleep duration over this period provides consistent results for increased risk of dementia in those with short sleep,” the researchers said.