Chronic insomnia promotes faster mental decline, dementia

People with chronic insomnia face an accelerated rate of cognitive decline and an increased risk of dementia, as shown in new research.

In an analysis of data from the population-based Mayo Clinic Study of Aging, insomnia was associated with a 0.011-per-year faster decline in global cognitive z-scores (95 percent confidence interval [CI], −0.020 to −0.001; p=0.028). This rate of decline corresponded to nearly 60 percent of the annual decline seen in people with the APOE e4 gene, according to first study author Dr Diego Carvalho from the Mayo Clinic in Rochester, Minnesota, US. [Neurology 2025;doi:10.1212/WNL.0000000000214155]

Notably, participants with chronic insomnia had a 40-percent greater risk of cognitive impairment (hazard ratio [HR], 1.4, 95 percent CI, 1.07–1.85; p=0.015), which was the equivalent of 3.5 additional years of ageing, Carvalho added.

“We saw faster decline in thinking skills and changes in the brain that suggest chronic insomnia could be an early warning sign or even a contributor to future cognitive problems,” he said.

Perceived sleep

Among participants with insomnia, those who reported having “reduced sleep” during the past 2 weeks were more likely to have poorer cognitive performance (p=0.012), a higher white matter hyperintensity (WMH) burden (p=0.005), and increased amyloid-PET levels (p=0.039) at baseline.

Carvalho pointed out that the magnitude of effect of WMH burden was comparable to being 4.5 years older, while the effect size of amyloid-PET levels was similar to that of being an APOE e4 carrier.

Meanwhile, participants with insomnia who reported “sleeping more” during the past 2 weeks had lower baseline WMH burden (p=0.028).

“Our study supports previous research suggesting that insomnia with objectively confirmed short sleep may be an important phenotype associated with cognitive impairment and extends these findings by indicating that even perceived reduced sleep may be relevant,” Carvalho said. [Sleep 2021;44:zsaa150]

He further emphasized that the negative effects of insomnia with reduced sleep on cognition and neuroimaging outcomes were already present at baseline, reflecting the chronic nature of the sleep disturbance, “which remains widely undiagnosed and undertreated in the community.”

Study details

In the study, 2,750 participants (mean age 70.3 years, 49.2 percent female) were included in global cognition analysis, and 2,814 in Cox models with a median follow-up of 5.6 years. A total of 1,027 and 561 participants were included in WMH and amyloid-PET analyses, respectively.

Insomnia was not associated with the rate of WMH or amyloid accumulation over time. Furthermore, the use of hypnotic medications did not influence cognitive performance (p=0.888) or the risk of cognitive impairment (HR, 0.94, 95 percent CI, 0.5–1.6; p=0.832).

The study was limited by the lack of objective sleep data, subjective quantitative sleep duration and insomnia severity, detailed hypnotic data (dose, duration of exposure, response to therapy, and side effects), and information on obstructive sleep apnoea severity and treatment, among others. Additionally, the cohort comprised more than 90 percent White participants, which may decrease the external validity of the findings to other racial or ethnic groups.

Taken together, the present data suggest that “insomnia may affect the brain in different ways, involving not only amyloid plaques, but also small vessels supplying blood to the brain. This reinforces the importance of treating chronic insomnia—not just to improve sleep quality but potentially to protect brain health as we age,” Carvalho said.

“Our results also add to a growing body of evidence that sleep isn’t just about rest—it’s also about brain resilience… Further studies should investigate the effects of treatment for insomnia and short sleep duration in the trajectory of cognitive decline and neuroimaging biomarkers, including specific classes of hypnotics and cognitive behavioural therapy,” he added.