Heart patients with weekly nightmares are five times more likely to feel depressed or anxious and even more likely to have difficulty sleeping compared to those without frequent nightmares, according to new research published in the European Journal of Cardiovascular Nursing.

“Health professionals should ask patients if they experience bad dreams as a warning sign for depression, anxiety, or trouble sleeping,” said study author Takashi Kohno, MD, of Keio University School of Medicine, Tokyo, Japan. “Psychological disorders and insomnia are linked with the development and progression of heart disease and upsetting dreams could be a clue that patients need extra prevention efforts.”

“Our study shows strong associations between depression, anxiety, insomnia, and bad dreams in patients with heart disease,” added Kohno. “As this was an observational study, it cannot determine the cause-effect relationship, but it may be bidirectional. In other words, depression, anxiety and insomnia may cause nightmares, and nightmares could lead to depression, anxiety and insomnia.”

The study included 1,233 patients admitted with various heart diseases to Keio University Hospital. The average age was 64 years and 25% were women. Nightmares, sleep and psychological characteristics were assessed with self-reported questionnaires and sleep-disordered breathing (when breathing stops and starts during sleep) was measured using overnight pulse oximetry (a measure of blood oxygen levels).

Nearly 15% of patients had at least one nightmare per month, and 3.6% had at least one nightmare per week (defined as frequent nightmares). Women were more likely to have frequent unpleasant dreams compared to men. Some 45.9% of patients reported insomnia, 18.5% had depression, 16.9% had anxiety, and 28.0% had sleep-disordered breathing.

Frequent nightmares were not associated with heart medications and sleep-disordered breathing, but were linked with depression, anxiety, and insomnia. Patients with weekly bad dreams were five times more likely to be depressed (odds ratio [OR]=4.61; 95% confidence interval [CI]=2.03-10.48), five times more likely to be anxious (OR=5.32; 95% CI=2.36-12.01), and seven times more likely to have insomnia (OR=7.15; 95% CI=2.41-21.22).

Kohno said: “The prevalence of nightmares and frequent nightmares in the general population, reported by other groups, is similar to the experience of heart patients in our study. We showed that in people with heart disease, women are more likely than men to have persistent bad dreams. This also mirrors findings in the general public. The strong associations among frequent nightmares, insomnia, and psychological disorders we observed reflects prior research in healthy people, suggesting that these relationships could be universal regardless of the presence of heart diseases.”