A new study has found that people who go on to develop motor neuron disease (MND) or frontotemporal dementia (FTD) may experience disrupted sleep patterns years before diagnosis, offering clues to possible early warning signs of the disease.

ALS (amyotrophic lateral sclerosis), the most common form of MND, affects nerve cells responsible for controlling movements. FTD is a form of dementia that primarily affects behaviour and language. Some people experience symptoms of both, a condition now recognised as ALS-frontotemporal spectrum disorder (ALS-FTSD). These overlapping conditions share symptoms, underlying biology, and genetic risk factors, and together form a disease spectrum.

Sleep disturbances might occur years before symptoms begin

The study, published in Translational Psychiatry, analysed health and lifestyle data from nearly 400,000 people who took part in the UK Biobank, a significant national research resource. None of the participants had MND or FTD when they enrolled, but over the next 14 years, 633 went on to be diagnosed with ALS, FTD, or ALS-FTD.

Researchers focused on the participants’ sleep patterns, using both self-reported questionnaires and, where available, wrist-worn devices to track movement and sleep. They then compared sleep habits in people who did or didn’t go on to receive a diagnosis.

They found that people who later developed ALS or ALS-FTSD were more likely to have had an “organic” sleep disorder, such as insomnia or sleep apnoea. These kinds of sleep problems were prevalent in men and people diagnosed before the age of 60. However, sleep disorders were still only present in a minority of those who developed the disease.

The study also found that extreme sleep durations were more common in people who went on to develop ALS or FTD. People who reported sleeping for less than five hours or more than eight hours were more likely to later develop ALS-FTSD than those who slept a typical 7–8 hours per night. Very short sleep was particularly linked to ALS, while long sleep was more strongly associated with FTD.

One interesting finding was that individuals who reported waking up easily in the morning were less likely to develop ALS-FTSD in the future. However, other aspects of sleep, such as being a morning or evening person, snoring, or napping, did not show a clear link with disease risk.

What does this mean for MND research?

These findings suggest that changes to sleep patterns could appear years before typical symptoms begin, raising the possibility that sleep issues could help researchers identify those at higher risk of developing ALS-FTSD in future.

Early diagnosis is essential in MND and FTD, as it allows people to access emerging treatments sooner and participate in clinical trials while the disease is still in its early stages. It also gives people more time to plan, make decisions, and access the proper support. If changes in sleep prove to be an early sign of disease, they could eventually support future screening or monitoring tools, especially for individuals with a known increased risk, such as those with a family history.

However, the researchers caution that their findings do not show a direct cause-and-effect link. It’s unclear whether disrupted sleep plays a role in triggering the disease or whether it’s one of the first symptoms caused by changes in the brain. Further research is needed to understand the potential relationship between them fully.

Still, this large-scale study is a significant step towards understanding early disease changes and could help inform future work on prevention, early detection, and risk management in ALS-FTSD.

This research snapshot was created using the University of Sheffield’s Readable Research series, which turns technical science into clear, meaningful updates for the MND community. A lay summary of the above research paper is available here.

Original study: Yang T, Shang H. Association between sleep and ALS-FTSD: A prospective cohort study based on 396,918 UK Biobank participants. Translational Psychiatry. 4 April 2025. DOI: 10.1038/s41398-025-03328-0