The research team found that even moderately irregular sleep doubles the risk of having another clinical event within six months, according to a study published on August 21 in the journal JACC Advances. A clinical event could be another visit to the emergency room, hospitalization or even death.

"Going to bed and waking up at consistent times is important for overall health," said lead author Brooke Shafer, Ph.D., a research assistant professor in the Sleep, Chronobiology and Health Laboratory in the OHSU School of Nursing. "Our study suggests that consistency in sleep timing may be especially important for adults with heart failure."

Researchers enrolled 32 patients who had been hospitalized for acutely decompensated heart failure at OHSU Hospital and Hillsboro Medical Center from September 2022 through October 2023. For one week following hospital discharge, participants used sleep diaries to record the time they fell asleep at night, woke up in the morning and the timing of naps they took during the day.

The participants were then categorized as regular sleepers or moderately irregular sleepers, based on their sleep patterns.

The study found:

• Following discharge from the hospital, 21 participants experienced a clinical event over the course of six months.
• Of that group, 13 were classified as moderately irregular sleepers compared with eight classified as having a regular sleep schedule.
• Statistically, the irregular sleepers had more than double the risk of an event across the six-month time span.

The increased risk of a clinical event for moderately irregular sleepers remained even when accounting for possible contributing factors like sleep disorders and other underlying medical conditions. The research team says the study is among the first to examine the impact of sleep regularity in the context of heart failure, and the findings add to a growing body of evidence suggesting the importance of maintaining a regular sleep schedule.

"Improving sleep regularity may be a low-cost therapeutic approach to mitigate adverse events in adults with heart failure," the authors conclude.

Shafer said the results strengthen the connection between sleep regularity and cardiovascular health.

"When we're asleep and in a resting state, our blood pressure and heart rate decrease compared with daytime levels," she said. "But variability in sleep timing may disrupt mechanisms involved in the regulation of the cardiovascular system. Irregular sleep may contribute to adverse outcomes, especially for people already affected by heart failure."

The next step would be to scale up the research to a larger cohort of participants and see whether improving sleep regularity lowers the risk of another clinical event, she said.

In addition to Shafer, co-authors include Shirin Hiatt, M.P.H., RN, Sophia Kogan, B.S.N., RN, Nathan Dieckmann, Ph.D., Christopher Chien, M.D., Quin Denfeld, Ph.D., RN, and Andrew McHill, Ph.D., all of OHSU; and Christopher Lee, Ph.D., RN, of Boston College.

The study was supported by the National Heart, Lung, and Blood Institute; the Eunice Kennedy Shriver National Institute of Child Health & Human Development; and the National Institute of Nursing Research, all of the National Institutes of Health, awards T32HL083808, K12AR084221 and R01NR019054, respectively; and the OHSU School of Nursing. The content is solely the responsibility of the authors and does not necessarily represent the official views of the NIH.

The research, led by McGill University scientist Masha Prager-Khoutorsky in collaboration with an interdisciplinary team at McGill and the Research Institute of the McGill University Health Centre, suggests the brain may be a missing link in certain forms of high blood pressure - or hypertension - traditionally attributed to the kidneys.

"This is new evidence that high blood pressure can originate in the brain, opening the door for developing treatments that act on the brain," said Prager-Khoutorsky, associate professor in McGill's Department of Physiology.

Hypertension affects two-thirds of people over 60 and contributes to 10 million deaths worldwide each year. Often symptomless, the condition increases the risk of heart disease, stroke and other serious health problems.

About one-third of patients don't respond to standard medications, which primarily target the blood vessels and kidneys based on the long-standing view that hypertension begins there. The study, published in the journal Neuron, suggests the brain may also be a key driver of the condition, particularly in treatment-resistant cases.

How salt disrupts the brain

To mimic human eating patterns, rats were given water containing two per cent salt, comparable to a daily diet high in fast food and items like bacon, instant noodles and processed cheese.

The high-salt diet activated immune cells in a specific brain region, causing inflammation and a surge in the hormone vasopressin, which raises blood pressure. Researchers tracked these changes using cutting-edge brain imaging and lab techniques that only recently became available.

"The brain's role in hypertension has largely been overlooked, in part because it's harder to study," Prager-Khoutorsky said. "But with new techniques, we're able to see these changes in action."

The researchers used rats instead of the more commonly studied mice because rats regulate salt and water more like humans. That makes the findings more likely to apply to people, noted Prager-Khoutorsky.

Next, the scientists plan to study whether similar processes are involved in other forms of hypertension.

"Microglia regulate neuronal activity via structural remodeling of astrocytes" by Ning Gu et al., was published in Neuron and supported by the Canadian Institutes of Health Research, Heart and Stroke Foundation of Canada and the Azrieli Foundation.