Frontotemporal dementia is an umbrella term covering several clinically distinct syndromes that share a common target: the frontal and temporal lobes of the brain. While the behavioural variant, marked by apathy, disinhibition, and loss of empathy, is the most widely recognised form, the temporal lobe variants present a different and often deceptive picture. The left-sided temporal variant, known as semantic variant primary progressive aphasia, erodes the patient’s knowledge of words, objects, and meanings, producing profound language difficulties while leaving other cognitive faculties relatively intact for years. The right-sided temporal variant, sometimes described in the literature as right temporal lobe atrophy, is even more elusive, producing subtle changes in personality, social conduct, and emotional processing that can be mistaken for psychiatric illness for years before a neurological diagnosis is made.

These syndromes have long been studied through the lens of language and behaviour, but a growing body of evidence suggests that sleep may offer an equally revealing window into the underlying disease. Previous work has documented sleep disturbances across the frontotemporal dementia spectrum, and researchers have proposed that the orexin system, a neuropeptide network in the hypothalamus that governs arousal and wakefulness, may be a key player. Studies have reported reduced orexin-A levels in patients with frontotemporal dementia, and a possible association between this loss and the severity of sleep disruption. More recently, investigators have linked changes in cerebral and hypothalamic structure to sleep dysfunction in people with genetic forms of the disease, raising the possibility that the hypothalamus, the brain’s master clock, is drawn into the neurodegenerative process earlier than previously appreciated.

The UCL-led study set out to address a conspicuous gap in this literature. Although sleep symptoms have been characterised in the behavioural variant of frontotemporal dementia and in Alzheimer’s disease, the temporal lobe variants have been largely overlooked, despite their distinctive pattern of brain atrophy. The research brought together a carefully characterised patient cohort from the Dementia Research Centre, where patients undergo detailed clinical, neuropsychological, and imaging assessment, and combined this clinical expertise with the sleep science methodology of the Surrey Sleep Research Centre, one of the United Kingdom’s leading centres for the study of human sleep and circadian rhythms.

Technically, the investigation relied on validated subjective sleep instruments, most notably the Pittsburgh Sleep Quality Index, a questionnaire widely regarded as the gold standard for capturing the multidimensional nature of sleep quality, spanning sleep duration, latency, disturbances, efficiency, and daytime dysfunction. The team also employed the Epworth Sleepiness Scale, a measure of generalised daytime sleepiness that quantifies the propensity to doze in everyday situations such as reading, watching television, or sitting in conversation. By applying these standardised tools to patients with temporal lobe variants, the researchers could characterise sleep disturbance in a way that is comparable with the wider dementia literature, allowing direct comparison with previous findings in behavioural variant frontotemporal dementia and Alzheimer’s disease.

The rationale for this approach is grounded in a broader conceptual shift in neurodegeneration research. Rather than viewing sleep disturbance as a mere consequence of dementia, an increasing number of researchers argue that sleep and circadian disruption may be intertwined with the disease process itself, potentially reflecting the spread of pathological protein deposits into sleep-regulating circuitry. In Alzheimer’s disease, excessive daytime napping has been linked to dementia risk in what may be a bidirectional relationship, with poor sleep promoting the accumulation of amyloid and amyloid pathology in turn fragmenting sleep. Whether a similar reciprocal dynamic operates in frontotemporal dementia remains an open question, but the involvement of the hypothalamus and the orexin system provides a plausible mechanistic bridge between temporal lobe degeneration and disordered arousal.

The temporal lobes themselves are not passive bystanders in this story. Anatomical studies have shown that the anterior and medial temporal structures, including the amygdala and hippocampus, are densely connected with hypothalamic and brainstem arousal systems, and that atrophy in these regions reshapes the networks that govern emotional and physiological states. In semantic variant primary progressive aphasia, tissue loss typically begins in the left anterior temporal lobe and progresses asymmetrically, while right temporal variant disease mirrors this pattern on the opposite side. Because these variants damage the temporal lobes in a relatively focal and lateralised fashion, they offer neurologists a natural experiment: by comparing sleep profiles across left- and right-predominant disease, researchers can begin to map which aspects of sleep regulation are tied to which temporal networks.

The clinical implications of characterising sleep disturbance in these patients are considerable. Sleep problems are among the most burdensome symptoms for family caregivers, frequently precipitating care home admission and compounding the behavioural symptoms that already strain daily life. If sleep disruption in temporal lobe variants follows a recognisable clinical signature, clinicians could screen for it systematically, counsel families proactively, and potentially intervene with targeted behavioural or pharmacological strategies. Moreover, because sleep symptoms may emerge early in the disease course, as has been suggested for the behavioural variant in recent polysomnographic work documenting altered nocturnal sleep dynamics in early-stage patients, they could serve as diagnostic clues in cases where the temporal variant syndrome is still masquerading as a primary psychiatric or language disorder.

The study also reflects a wider trend toward interdisciplinary collaboration in dementia research. The partnership between the UCL Dementia Research Centre, with its decades of expertise in rare dementia syndromes, and the Surrey Sleep Research Centre, with its deep methodological grounding in circadian physiology, exemplifies the kind of cross-disciplinary approach that the field increasingly demands. The work was supported by Alzheimer’s Research UK, the Alzheimer’s Society, the Royal National Institute for Deaf People, and the National Institute for Health and Care Research University College London Hospitals Biomedical Research Centre, alongside a Frontotemporal Dementia Research Studentship funded through The National Brain Appeal. The authors, including joint senior authors Jason D. Warren and Jessica Jiang, report no conflicts of interest, and the study received ethical approval from the joint research ethics committees of University College London, the University of Surrey, and the National Hospital for Neurology and Neurosurgery, with all participating patients giving written informed consent.

For patients and families affected by these rare temporal lobe dementias, the message is one of cautious optimism. Sleep, long relegated to the margins of the clinical conversation, is now being taken seriously as a core feature of the disease, one that may illuminate both the mechanisms of neurodegeneration and the practical realities of daily care. As the evidence base grows, the hope is that a better understanding of sleep disturbance in temporal lobe variants of frontotemporal dementia will translate into earlier diagnosis, more comprehensive symptom management, and, ultimately, therapies that target the sleep-regulating circuits caught in the path of the disease. The full findings are published in the Journal of Neurology, and the datasets generated during the study are available from the corresponding author in anonymised form on reasonable request, in keeping with the ethical and confidentiality requirements that govern research with this vulnerable patient population.

Subject of Research: Sleep disturbance in temporal lobe variants of frontotemporal dementia

Article Title: Clinical features of sleep disturbance in temporal lobe variants of frontotemporal dementia

Article References: Larsen, E. K., Levett, B. A., Core, L. B., della Monica, C., Hassanin, H., Atzori, G., Harding, E., Dijk, D.-J., Revell, V. L., Eriksson, S. H., Rohrer, J. D., Warren, J. D., & Jiang, J. (2026). Clinical features of sleep disturbance in temporal lobe variants of frontotemporal dementia. Journal of Neurology, 273(9), Article 558. https://doi.org/10.1007/s00415-026-14104-5

Image Credits: AI Generated

DOI: 10.1007/s00415-026-14104-5

Keywords: frontotemporal dementia, sleep disturbance, temporal lobe atrophy, semantic variant primary progressive aphasia, orexin, hypothalamus, Pittsburgh Sleep Quality Index, Epworth Sleepiness Scale, neurodegeneration, circadian rhythms, dementia care, Journal of Neurology