We spend a third of our lives asleep. And a quarter of our time asleep is spent dreaming. So, for the average person alive in 2022, with a life expectancy of around 73, that clocks in at just over six years of dreaming.

Yet, given the central role that dreaming plays in our lives, we still know so little about why we dream, how the brain creates dreams, and importantly, what the significance of our dreams might be for our health – especially the health of our brains.

My latest study, published in The Lancet’s eClinicalMedicine journal, shows that our dreams can reveal a surprising amount of information about our brain health. More specifically, it shows that having frequent bad dreams and nightmares (bad dreams that make you wake up) during middle or older age, may be linked with an increased risk of developing dementia.

In the study, I analysed data from three large US studies of health and ageing. These included over 600 people aged between 35 and 64, and 2,600 people aged 79 and older.

All the participants were dementia-free at the start of the study and were followed for an average of nine years for the middle-aged group and five years for the older participants.

At the beginning of the study (2002-12), the participants completed a range of questionnaires, including one which asked about how often they experienced bad dreams and nightmares.

I analysed the data to find out whether participants with a higher frequency of nightmares at the beginning of the study were more likely to go on to experience cognitive decline (a fast decline in memory and thinking skills over time) and be diagnosed with dementia.

Weekly nightmares

I found that middle-aged participants who experienced nightmares every week, were four times more likely to experience cognitive decline (a precursor to dementia) over the following decade, while the older participants were twice as likely to be diagnosed with dementia.

Read more: https://theconversation.com/nightmares-are-a-good-predictor-of-future-dementia-new-study-191016