Many scientists now believe that long term insomnia is more than just an annoyance. It may be a real risk factor for Alzheimer’s disease and other forms of dementia. Research in the past few years has started to show clearer links between how we sleep and how our brains age over time.
What do we mean by long term insomnia
Insomnia is usually defined as trouble falling asleep, staying asleep, or waking up too early, at least three nights a week, for several months or longer. When this pattern goes on for years, it is often called chronic or long term insomnia. People with chronic insomnia may sleep only a few hours a night, or their sleep is broken into many short segments.
Short spells of poor sleep happen to almost everyone and are not the main concern. The real worry is when insomnia becomes a lasting pattern that the brain has to live with for years.
What recent studies are finding
Several modern studies point to insomnia and other sleep problems as possible risk factors for dementia, including Alzheimer’s disease.
Medical News Today reported on a large study that followed 2,750 older adults, most around age 70, who were cognitively healthy when the study began. About 16 percent had chronic insomnia. Over an average of 5.6 years, the researchers found that people with chronic insomnia had about a 40 percent higher chance of developing dementia or mild cognitive impairment compared with people who did not have chronic insomnia. This increased risk was similar to being about 3.5 years older in brain age or having multiple health problems such as high blood pressure and diabetes, which are already known dementia risks. You can read about this research in more detail at Medical News Today: https://www.medicalnewstoday.com/articles/sleep-quality-insomnia-sleep-apnea-increase-dementia-risk-latest-evidence.
Another Medical News Today article looked at circadian rhythm, the 24 hour internal clock that guides when we feel awake and when we feel sleepy. It described a Neurology journal study that used movement patterns as a marker of people’s daily rhythms. Weaker rhythms and more broken day and night patterns were linked to a higher risk of later dementia. For example, every standard step down in rhythm strength was linked to a 54 percent higher dementia risk, and people whose main activity peak came later in the day had a 69 percent higher risk than people with a more typical pattern. These findings suggest that not only how long we sleep, but also how regular and well timed our sleep and activity are, may matter for brain health. That article is here: https://www.medicalnewstoday.com/articles/body-clock-disturbances-may-contribute-to-dementia-risk-evidence-suggests.
Scientists writing in Alzheimer’s & Dementia have also noted that sleep disturbances, including insomnia and sleep disordered breathing, are increasingly viewed as modifiable risk factors for Alzheimer’s disease, not just symptoms of the disease once it has started. Their work discusses how changes seen on brain imaging and in Alzheimer’s biomarkers relate to sleep problems. You can see the abstract of that work here: https://alz-journals.onlinelibrary.wiley.com/doi/10.1002/alz70856_099181.
Other research has examined how sleep affects specific Alzheimer’s related proteins. The African Journal of Biomedical Research summarized evidence that even one night of severe sleep loss can raise the level of amyloid, a protein that forms the plaques seen in Alzheimer’s disease, in the brain. Ongoing sleep disturbance has been linked to higher amyloid burden over time. That article is available here: https://africanjournalofbiomedicalresearch.com/index.php/AJBR/article/view/9049.
A study of older women at risk for Alzheimer’s disease, published on the PubMed Central site, found that longer sleep duration was linked to greater resistance to and resilience against tau related brain changes. Tau is another key protein involved in Alzheimer’s. The authors suggested that good sleep may help the brain cope better with disease processes, even in people already at risk. You can explore this study at https://pmc.ncbi.nlm.nih.gov/articles/PMC12745661/.
Clinicians who focus on sleep medicine also warn about long term effects of insomnia on brain function. For example, a detailed overview from a sleep clinic explains that chronic insomnia prevents the brain from fully resetting at night, which can impair memory, concentration, and emotional regulation and may increase long term cognitive risk. That explanation can be found at https://sleeplessinarizona.com/can-insomnia-damage-brain-health/.
How poor sleep might contribute to Alzheimer’s disease
Researchers are still working out exactly how insomnia could contribute to Alzheimer’s risk, but several plausible biological pathways are being studied.
One important system is the brain’s glymphatic system. This is a network that helps clear waste products from the brain, including amyloid and tau, more actively during deep sleep. Medical News Today describes research using MRI scans showing that people with weaker glymphatic function had a higher dementia risk and that improving this clearing system could potentially lower the risk of dementia. You can read about that in the same Medical News Today piece on sleep quality and dementia risk: https://www.medicalnewstoday.com/articles/sleep-quality-insomnia-sleep-apnea-increase-dementia-risk-latest-evidence. If insomnia repeatedly cuts short deep sleep, the brain may have less time each night to remove these toxic proteins, which could lead to buildup over years.
Circadian rhythm disruption is another possible pathway. When people with long term insomnia go to bed and wake up at very irregular times, or lie awake for hours at night and nap during the day, their internal clock may drift out of alignment with the external light and dark cycle. The Neurology study summarized by Medical
