Examining the links between sleep problems and MND/ALS and dementia

ALS / motor neurone disease and dementia are diseases caused by the loss of cells in the nervous system. ALS (amyotrophic lateral sclerosis) leads to a loss of muscle function and frontotemporal dementia (FTD) is a form of dementia associated with personality alterations and language difficulties.

They share some symptoms and genetic characteristics, with some people showing signs of both diseases at the same time. Thus, these two diseases are considered as a spectrum, called amyotrophic lateral sclerosis-frontotemporal spectrum disorder (ALS-FTSD). Life expectancy varies but is on average 6-7 years from FTD diagnosis, 3 years from diagnosis of FTD and ALS together, and less than 2 years from ALS diagnosis.

Why is the study important?

There are many risk factors for ALS-FTSD, including disorders such as sleep problems, which can also contribute to a faster disease progression. Sleep changes can alternatively be a result of ALS-FTSD, and may be an early symptom. A lot is unknown about the relationship between sleep and ALS-FTSD. To explore this, this study looks at how common sleep disorders are in people who go on to develop ALS-FTSD, and how sleep characteristics may change during the course of the disease.

What did the authors do and how did they do it?

The authors used data from the UK Biobank, which recruited over 500,000 participants. The data contained disease diagnoses as well as lifestyle information, including wrist-worn physical activity monitors. Participants took a questionnaire on sleep characteristics, such as sleep duration and napping behaviour, and the activity monitors recorded sleep and wake times.

Where possible, these activity monitors were used for a more precise measurement of sleep and wake, but the self-reported information from the questionnaires was more common. Participants were excluded from this study if they reported an ALS or FTD diagnosis at recruitment (leaving 396,918 participants), but new diagnoses at later follow-ups were recorded (on average 14 years after recruitment, 633 people with a new ALS-FTSD diagnosis).

Sleep characteristics recorded at recruitment were compared between individuals with or without an ALS-FTSD diagnosis by the time they were followed up. The impacts of age, sex, and ethnicity were investigated, followed by other factors such as body mass index (BMI), socioeconomic status, and physical activity.

Organic sleep disorders – nervous system diseases including insomnia and sleep apnea – were more common in those who went on to be diagnosed with ALS and, to a lesser extent, FTD. Nonetheless, only a minority of the participants developed ALS or FTD during the study (less than 5% of people with either diagnosis). This was more common in people under 60, and more common in males than females. Nonorganic sleep disorders – behavioural disorders not caused by a substance or physical condition, such as sleepwalking and night terrors – were not associated with either ALS or FTD, with no individuals reporting such a disorder alongside ALS-FTSD diagnosis.

The duration of sleep was found to be altered in participants who developed ALS-FTSD. A smaller proportion of individuals reported ‘normal sleep’ (7-8 hours) than in the group without ALS-FTSD. Both ‘extreme short sleep’ (less than 5 hours) and ‘excessive sleep’ (over 8 hours) were more common in people with ALS-FTSD, especially in those over 60 years old. Even after considering physical and lifestyle differences, ‘extreme short sleep’ was twice as common in those with ALS and ALS-FTSD, and ‘excessive sleep’ was much more highly reported in people with FTD.

Characteristics of sleep were also assessed. Waking up easily in the morning was linked with people being less likely to develop ALS-FTSD. A person’s chronotype – e.g. morning person vs evening person – was not related to disease, nor were napping, dozing, or snoring.

What do the findings mean going forward for people with the disease?

If certain sleep alterations are an early sign of ALS-FTSD risk, they may eventually help some individuals seek medical advice before physical difficulties begin. This could be potentially useful for people who are advised by specialist MND clinics that they may fall into a higher-risk group, such as some individuals who are athletes in contact sports, are military veterans, or have a family history of ALS-FTSD diagnoses.

Given that the window for possible treatment is short, an earlier diagnosis may allow for more timely and effective care when therapies become available. In addition, earlier diagnosis could facilitate better preparation for people with ALS-FTSD and their families, and more opportunities to engage with research such as clinical trials.

However, this study comes several steps before such benefits. Although it discusses sleep disorders “causing” ALS-FTSD and sleep characteristics such as easy waking being “protective”, no direct link was investigated. The data show that good sleep may be associated with a lower chance of an ALS-FTSD diagnosis, and sleep disturbances may be more common in people who go on to develop ALS-FTSD. Nonetheless, this may instead be an early sign of disease or something that worsens disease progression. Although more direct investigation is needed to get a clearer answer, this study’s findings are an interesting start.

This study can be found at
https://www.nature.com/articles/s41398-025-03328-0

Paper title
Association between sleep and ALS-FTSD: A Prospective Cohort Study based on 396,918 UK biobank participants

Lead author
Tianmi Yang, Huifang Shang

Publication details including date of publication
Published in Translational Psychiatry on 04 April 2025. DOI 10.1038/s41398-025-03328-0