Women, circadian rhythms and heart disease

Research shows that body clocks underlie women’s resilience to heart disease
Woman with insomnia touching alarm clock

New understanding of differences in how men and women respond to chronic circadian rhythm and sleep disruptions could change how we treat heart disease. 

Research shows disrupting your body clock or circadian rhythms accelerates heart aging, and increases your risk of heart disease. A new study led by Heart & Stroke cardiovascular researcher Dr. Tami Martino is the first to show how women may be better protected even when their circadian rhythms are disrupted. These findings could open the door to new therapies for living longer and healthier lives.

As Dr. Martino and her team at the University of Guelph in Ontario discovered, the circadian body clock has a direct impact on heart function. Body clocks regulate our day and night body processes, essentially helping us know when to be awake and active, or rest and sleep. They do this by coordinating the molecules in our cells, including in our heart cells, optimizing our processes to the time of day or night when they are most needed. 

Disturbing these clocks drives heart disease. The circadian clock is fundamentally important for our cardiovascular health, Dr. Martino explains.

Hormones affect body clocks

These body clocks interact with male and female hormones, leading to differences in the actual construction of the heart, which in turn influence how the heart functions and how resilient someone is to heart disease. 

Female ovarian hormones were found to have a protective effect which, Dr. Martino notes, helps explain why fewer women experience heart disease before menopause. In experimental studies, Dr. Martino observed that female mice are protected from heart disease, even when the body clock is disrupted. In contrast, female hearts begin rapidly aging if the hormones are removed. “They reacted exactly like male mice with disrupted clocks, they lost the heart health protection,” she says. 

Tami Martino

These findings are an exciting confirmation of how women differ.

Dr. Tami Martino Heart & Stroke researcher

The challenge facing many women is that they're living longer lives, much past menopause, in a world that increasingly operates as a 24/7 environment. For example, light at night from our phones, computers, shift work and other sources conspire to disrupt our circadian and sleep cycles. These have profound implications for heart health as we age. 

New field, new treatments

“What we are focusing on with these latest findings is how the heart’s circadian biology can be therapeutically manipulated,” Dr. Martino says. “We are developing a new field called circadian medicine, to protect women as they get older and also to identify treatments that will better protect men as well.”

She adds: "These findings are an exciting confirmation of how women differ, and how circadian medicine based on the science of sex differences can lead to new therapies to prevent, slow or reverse heart disease.”