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Although scientists still debate why we dream, a 2022 Lancet study has uncovered a striking link between frequent nightmares and an increased risk of cognitive decline and dementia.
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Dreams occur during REM sleep, a phase in which brain activity approaches waking levels and heart rate and blood pressure rise. Nightmares, defined by the Sleep Foundation as vivid, threatening or disturbing dreams that awaken the sleeper, are most common in REM and typically remembered upon waking. Unlike night terrors, which arise during deep NREM sleep, nightmares are usually experienced by all age groups, though children aged 3‑6 report them most often.
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The research, titled “Distressing dreams, cognitive decline, and risk of dementia: A prospective study of three population‑based cohorts,” followed 3,200 participants across three large ageing studies. At baseline, all were dementia‑free and reported the frequency of bad dreams. Middle‑aged adults (35‑64) were monitored for an average of nine years; older adults (≥79) for five years.
Analysis by Dr. Abidemi Otaiku, a clinical research fellow at Imperial College London, revealed that those who reported weekly nightmares had a four‑fold increase in the odds of later cognitive decline compared with those reporting none. In the oldest cohort, the risk of developing dementia doubled, and the association was even stronger in men—those with weekly nightmares were five times more likely to develop dementia, while women’s risk rose by only 41%.
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Whether nightmares trigger cognitive deterioration or simply flag underlying brain changes remains unclear. The study’s authors emphasize the need for longitudinal research to determine causality. Nevertheless, the findings suggest that nightmares could serve as one of the earliest detectable signs of neurodegeneration, potentially preceding classic memory loss by years or even decades.
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If nightmares are indeed a harbinger of dementia, treating them in middle age could reduce future disease burden. Dr. Otaiku plans to explore whether early‑life nightmares predict later‑life dementia risk and to investigate how dream recall and vividness correlate with cognitive trajectories. This line of inquiry may ultimately open new avenues for pre‑symptomatic intervention and deepen our understanding of dreaming’s biological role.
