Our biological clock (circadian system) governs many physiological processes, including blood pressure. Blood pressure normally dips at night. People who do not experience this temporary drop (called "non-dippers") are at increased risk for developing heart disease. Researchers discovered that one of four main genes comprising the circadian system act differently in men and women. They found that male mice missing this gene (PER1) become non-dippers and have a higher risk of heart and kidney disease. In contrast, female mice missing the PER1 gene continue to show normal dips in blood pressure at night (American Journal of Physiology-Regulatory, Integrative and Comparative Physiology
, January 2019 ahead of print). This phenomenon may explain in part why premenopausal women, who are less likely to be non-dippers than men of the same age, have a lower risk of heart disease. After menopause, their risk climbs due to other factors and quickly erases this biological benefit.