Tokyo, Dec 17 (IANS): 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, say researchers.

According to the study, published in the European Journal of Cardiovascular Nursing, 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," said study author Takashi Kohno from the Keio University in Japan.

"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," Kohno added.

Previous research has shown that frequent nightmares are associated with sleep and psychological disorders in the general population.

This was the first study to investigate this relationship in patients with heart diseases. It also examined whether heart medications were connected with unpleasant dreams.

The study included 1,233 patients admitted with various heart diseases to Keio University Hospital. The average age was 64 years and 25 per cent 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).

The findings showed that nearly 15 per cent of patients had at least one nightmare per month, and 3.6 per cent 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 per cent of patients reported insomnia, 18.5 per cent had depression, 16.9 per cent had anxiety, and 28.0 per cent 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, five times more likely to be anxious and seven times more likely to have insomnia.

"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," the researchers said.

"Nightmares may be an alert for underlying psychological or sleep problems that should be addressed to avoid new, or worsening, heart problems. Healthcare professionals should include a question about bad dreams in their assessments," the authors noted.