Night-Time Heat Stress, Ageing and Neurodegeneration - The Next HOT Topic

Abstract

Global warming is intensifying exposure to extreme heat, creating a growing but under-recognised threat to brain health in later life. Older adults, particularly those with or at risk of neurodegenerative disease, are uniquely susceptible because ageing and neuropathology can impair thermoregulation, sleep, vascular and inflammatory homeostasis, and the capacity to recognise and respond to heat stress. This vulnerability may be greatest at night, when elevated temperatures can disrupt sleep architecture, limit physiological recovery, and prolong thermal strain. In this narrative review, we (1) describe mechanisms of heat vulnerability in normative and pathological ageing (2) synthesise epidemiological studies linking ambient temperature, heatwaves, and warm nights with dementia-related mortality, hospitalisation, emergency care, and cognitive outcomes, while noting limitations in exposure assessment, confounding, diagnostic specificity, and causal inference (3) propose a “hotter nights–sleep disruption–neurodegeneration” pathway as a plausible framework for future research (4) outline management implications, including targeted sleep and heat advice, medication review, caregiver planning and cooling strategies. Testing this proposed pathway will require bedroom-level exposure assessment and longitudinal designs that measure heat, sleep and brain health together, rather than the outdoor-temperature proxies and siloed studies that dominate current evidence. Night-time heat warrants anticipatory, function-based clinical care alongside housing, urban-cooling and heat-health policy measures that protect sleep and cognitive resilience as the climate warms.