Chronic insomnia could speed up brain ageing. But by how much?

Chronic insomnia could be bad for more than just your sleep schedule – it could speed up brain ageing, new research has found.

People with chronic insomnia, or those who have trouble sleeping at least three nights per week for three months or more, are 40 per cent more likely to develop dementia or mild cognitive problems than people who sleep normally, according to the study published in the journal Neurology.

That translates to an additional 3.5 years of brain ageing, the study said.

The findings “add to a growing body of evidence that sleep isn’t just about rest – it’s also about brain resilience,” Dr Diego Z. Carvalho, one of the study’s authors and a neurologist at the US-based Mayo Clinic, said in a statement.

Carvalho’s team tracked 2,750 older Americans who were cognitively healthy over an average of nearly six years. The participants – 16 per cent of whom were diagnosed with insomnia – underwent regular memory and thinking tests, and some had brain scans.

Overall, 14 per cent of people with insomnia developed dementia or mild cognitive impairment, compared with 10 per cent of those without insomnia. People with chronic insomnia also saw sharper declines on thinking tests over the years.

“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,” Carvalho said.

The findings held up even after the researchers accounted for factors such as age, high blood pressure, sleep apnoea, and the use of sleep medications.

Notably, though, they did not prove that insomnia causes brain health issues, just that the two are related. More studies will be needed to understand exactly why they seem to be linked.

The study also found that chronic insomnia seems to affect some people’s brain health more than others.

Participants who said they were getting less sleep than usual had more white matter hyperintensities, or bright spots on brain scans that signal damage, and amyloid plaques, or proteins that can build up in the brain and have been linked to Alzheimer’s disease.

Their amyloid plaque levels were similar to those typically seen in people who carry the APOE4 gene variant, which raises the risk of Alzheimer’s, the study found.

Participants with the APOE4 variant also saw bigger declines in memory and thinking skills.

“Our results suggest that insomnia may affect the brain in different ways, involving not only amyloid plaques, but also small vessels supplying blood to the brain,” Carvalho said.

The findings are the latest to find a link between sleep and brain health. Chronic sleeplessness and poor sleep quality also raise the risk of high blood pressure, heart disease, diabetes, depression, and obesity.

Dementia affects about 57 million people worldwide, according to the World Health Organization (WHO). Insomnia affects an estimated 16.2 per cent of people in countries with quality data available.

The latest study “reinforces the importance of treating chronic insomnia – not just to improve sleep quality but potentially to protect brain health as we age,” Carvalho said.