‘Heart patients with sleep issues at higher risk of cardiac arrest’

Novel study links poor sleep and heart failure in patients with pre-existing heart condition.

Bengaluru: Although links between poor sleep quality and increased cardiovascular health risks have long been debated, a recent study, conducted between 2021 and 2024, by researchers at the Institute for Stem Cell Science and Regenerative Medicine (inStem), Bengaluru, shows how sleep fragmentation can induce heart failure in patients with pre-existing heart muscle conditions such as hypertrophic cardiomyopathy (HCM).

HCM is mainly caused by a gene mutation or abnormality in the heart’s muscle, which causes the heart’s left ventricle walls to thicken, affecting the heart’s ability to pump blood properly. 

Researchers at inStem tested the hypothesis that sleep fragmentation (SF) is a risk factor for heart failure in HCM patients. They note that HCM can go largely undiagnosed  due to rudimentary genetic testing in the country and because many people don’t seek help until symptoms of breathlessness, chest pain, fatigue, irregular heartbeat or puffiness of limbs prompt testing.

“Indian adults are genetically more prone to developing HCM due to high frequency of inbreeding, which is established in several studies,” Dr Dhandapany Perundurai, Associate Professor and Scientist F, inStem, told DH.

“Many HCM patients die of heart failure and sudden cardiac arrests. However, the reasons remain unclear. Therefore, we conducted the study to know the influence of sleep on such patients,” he said.

He added that the link between HCM and many lifestyle factors such as diet, stress, pollution and exercise, that influence heart disease in general, have not been adequately studied to show any direct impact on HCM.

DH exclusively accessed a draft of the paper, which showed that researchers from inStem studied the effects of chronic sleep disturbances on a genetically modified mice model, where the myosin binding protein C3 (MYBPC3) variant specific to Indian patients of HCM was introduced to two groups of mice, one of which was subjected to sleep disturbances. 

Two other control groups of mice did not have HCM, and one of the groups was also subjected to sleep disturbances to draw comparisons. Mice were kept inside cabinets fixed to a shaker that shook the cabinet at fixed allowable intervals of a few seconds, thus disturbing their sleep.

After several weeks of chronic sleep disturbances, the heart pumping capacity in HCM mice deteriorated to heart
failure.

This novel study indicated that HCM patients with short sleeping periods, continuous external disturbances, and sleep disorders such as insomnia will show cellular-level damage, especially mitochondrial structure damage, muscle fibre weakening and cell death.

“Our findings for the first time show that sleep fragmentation is a risk factor for heart failure transition and have important implications in clinical settings where HCM patients with sleep disorders have worse prognosis,” noted the study.

The study recommends that patients with cardiac disorders follow proper regularised sleep habits to avoid adverse effects such as heart failure or sudden death. “Adults should adopt at least seven hours of regular sleep without interruption for a healthy heart,” noted Dr Perundurai.