Had a nightmare last night? That’s not a good sign for your health

Night hags and nightmares. Succubi and incubi. Sleep has long been a demon-haunted world. In olden days, such visitations were thought to drain the dreamer of life-energy and, though modern science has no truck with actual demons, the fear that bad dreams somehow sap a dreamer’s health has not vanished. Instead, it has been confirmed.

Almost everyone has nightmares. But it is among those who have them weekly – somewhere between 2 per cent and 6 per cent of the population – that connections with ill-health seem to arise.

Some links are to be expected. Depression, anxiety, schizophrenia and post-traumatic-stress disorder, for example, all have nightmares as a common symptom. The same goes for chronic pain. But other connections are more mysterious. Research by Abidemi Otaiku at Imperial College London suggests that nightmares may warn of neurological illnesses, such as Parkinson’s disease and dementia. And other groups have shown that conditions not specifically brain-related, including cardiovascular problems and autoimmune diseases such as lupus, seem linked to nightmares, too.

Worst of all, nightmares may kill. Otaiku’s latest work, presented last month at a conference in Helsinki, shows frequent nightmares are stronger predictors of early death than smoking, obesity, poor diet or sloth.

To arrive at his conclusion, Otaiku analysed six long-term studies from America and Britain, involving more than 180,000 adults and almost 2500 children. Those whose nightmares were weekly or more frequent were three times more likely to die before the age of 70 than those who had them less than once a month. Out of 174 people who died prematurely, 31 had at least weekly nightmares.

Part of the explanation is his finding that the chromosomes of the nightmare-prone show signs of accelerated ageing of a sort that can be brought about by stress hormones, which nightmares are known to promote. These chromosomal effects, he reckons, are responsible for about 40 per cent of the increased risk of premature death in those prone to nightmares. Where the other 60 per cent comes from is unknown.

All of this suggests that paying attention to nightmares is a good idea. Where they are a symptom, they can give warning of what is coming. And where they are a cause, treatments to reduce nightmares can be undertaken as a priority.

That is not to say the two are always easy to distinguish. In the cases of depression, anxiety and so on, nightmares are both symptom and cause. Bad dreams triggered by psychiatric disturbance induce stress that reinforces the underlying condition. For conditions such as Parkinson’s and dementia, though, which are caused by neurological damage, nightmares are unlikely to be anything other than symptomatic.

The same may well hold true for lupus, a condition in which the immune system attacks healthy organs, including the brain, promoting inflammation. That may well trigger nightmares, with any stress hormones released as a consequence likely to make things worse.