Sleep Disorders an Early Dementia ‘Warning Sign’?


Sleep disturbances are associated with a 17% increased risk of dementia, according to a large registry-based study.

Dr. Gunhild Waldemar

“We cannot rule out a diagnosis of a sleep disorder from our study, which in many cases is a precursor to dementia,” says researcher Gunhild Waldemar, MD, Professor of Clinical Neurology at the Faculty of Health and Medical Sciences at the University of Copenhagen. Denmark, Medscape Medical News reported.


She added that the findings should serve as a reminder to clinicians of the importance of early diagnosis and treatment of the sleep disorder to reduce a patient’s risk of developing dementia in the future.

The results were presented at the Alzheimer’s Association International Conference (AAIC) 2022.

Growing evidence base

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Previous research has identified a wide range of modifiable risk factors for dementia, and a growing body of evidence suggests sleep disturbances are among them.

However, studies examining the links between poor sleep and dementia have often been based on relatively small cohorts, short time intervals, retrospective surveys, or self-reported exposure data, Waldemar noted.

“Our study is based on a nationwide cohort of people and it includes everyone because we have full health coverage in Denmark. Thus, there are no missing persons or those who have left,” she said.


The study data were obtained from large comprehensive Danish health registries and included individuals born between 1928 and 1953 who were followed up for 40 years after reaching the age of 50, from January 1, 1978 to December 31, 2018.

The researchers linked population data with information about hospital diagnoses of sleep disorders and hospital late dementia in people over 65 years of age. 50, somatic and mental illness.

About 1.49 million people took part in the study. Of these, 41,704 people were diagnosed with a sleep disorder. The percentage was higher in men (69.1%) than in women (30.9%).


During the follow-up period, 1235 participants (3%) were diagnosed with dementia. The median age at first diagnosis of dementia was 75.6 years.

The results showed a significant 17% increased risk of dementia with any sleep disorder (adjusted IRR, 1.17; 95% CI, 1.11–1.24). The risk was mostly among men, although there was a weaker, negligible risk among women.

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Among the 28,327 participants with sleep apnea, the risk of developing dementia was increased by 13%, but this was also only significant for men. Waldemar noted that sleep apnea is much more common in men than women, perhaps because they are more likely to be overweight and have lung disease.


Two possible interpretations

The category “other specific sleep disorders” included insomnia, hypersomnia, non-organic sleep disorders, sleep-related movement disorders, and parasomnia. For men with “other specific sleep disorders”, the IRR was 2.0 (95% CI, 1.71–2.32).

Because parasomnia is a known early symptom of some dementias, including Parkinson’s disease and Lewy body dementia, the researchers excluded them from analysis. After exclusion, the IRR for dementia in those with “other sleep disorders” was 1.4 (95% CI, 1.21–1.62).

In terms of age groups, the researchers found that those over the age of 65 had the highest risk. An assessment of the risk of developing dementia within 5 years and 5 years after the diagnosis of sleep disorder showed that the risk increased by 35% during the first 5 years (IRR, 1.35; 95% CI, 1.21–1.62).

“So basically in the first 5 years after a sleep disorder diagnosis, we saw an increased risk,” Waldemar said.

She said there are two possible interpretations of the results: either sleep disturbances are a risk factor for dementia in the future, or they are a very early symptom of dementia.

Determining which interpretation is more accurate “is not black and white,” she said. In some cases, receiving a diagnosis of a sleep disorder may also mean receiving a diagnosis of dementia within the next 5 years, Waldemar said, while in other cases, a diagnosis of a sleep disorder may indicate a long-term risk factor.

A possible mechanism involves the lymphatic system, which flushes toxic compounds, including beta-amyloid, from the brain during sleep.

Waldemar noted that although the study was based on strong and reliable data from nationwide registries and had a long follow-up period, it has some limitations. For example, data are collected only from inpatient and outpatient hospital contacts and not from primary care.

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In addition, the study did not include detailed information about how long people slept, the quality of their sleep, or the different types of dementia, Waldemar added.

Nothing new?

Commenting on the study, Christian Steen Frederiksen, MD, director of clinical trials at the Danish Dementia Research Center in Copenhagen, Denmark, told Medscape Medical News that the results are highly “reliable” and based on a “very large sample.” “Danish population.

“Physicians should be vigilant about older patients who develop sleep disturbances, as this can be a precursor to dementia,” said Frederiksen, who presented the main findings from dementia research at the European Academy of Neurology meeting.

However, Frederiksen noted that the registry-based study could be subject to possible bias, for example by underreporting certain sleep disorders.

Also to Medscape Medical News, clinical neurologist David Knopman, MD, Mayo Clinic, Rochester, Minnesota, said there is a stronger short-term risk of dementia after a diagnosis of a sleep disorder, but weaker evidence for long-term risk is “key.” find.

“This could potentially point to sleep disturbances as an early symptom of dementia,” said Knopman, whose research focuses on cognitive impairment in later life.

However, apart from the fact that disrupted nighttime sleep is a “likely” early symptom of dementia, “I wouldn’t go into details,” he said.

“The study says nothing about the mechanisms of the disease. In particular, this work does not contain information on amyloid clearance,” he added.

Knopman also noted that he did not consider this study particularly newsworthy. “Sleep disturbance is well known as an early symptom of dementia,” he said.

Waldemar has worked as a consultant/speaker for Roche, Biogen and Novo Nordisk. Nopman has not disclosed any relevant financial relationships.

Alzheimer’s Association International Conference (AAIC) 2022: abstract 63813. Submitted August 2, 2022.

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