At night, the heart does not stop working. It keeps beating while the rest of the body moves through sleep, waking, and the shifting rhythms that govern blood pressure and metabolism. That rhythm of the body can become unsettled when sleep becomes too short or broken. A large UK Biobank study involving 72,269 participants found that people with very irregular sleep times had a significantly higher risk of major adverse cardiac events, even when they were getting adequate sleep. A 2026 study involving 3,231 middle-aged participants from the Northern Finland Birth Cohort found that among people sleeping less than eight hours a day, irregular bedtime or sleep midpoint was associated with twice the risk of major adverse cardiac events.
The findings reflect how closely sleep is tied to the body's internal clock, says Dr Karthik Madesh Ratnavelu, director and head of Advanced Institute for Sleep Health at SIMS Hospital, Chennai. “The body functions through a circadian rhythm which controls such processes as sleep, wakefulness, hormone secretion, body temperature, metabolism, blood pressure, and heart functions,” shares Dr Karthik.
“While sleep requirements can vary with age and individual needs, maintaining adequate and regular sleep is important across adulthood. In older adults, if nighttime sleep is inadequate or fragmented, a short daytime nap can also be helpful. What is important is to ensure that daytime napping does not interfere with nighttime sleep,” says Dr Monica Kumbhat M, pathologist, Neuberg Diagnostics.
Someone can spend eight hours in bed and still have poor sleep because snoring, obstructive sleep apnoea, heartburn, restless legs, or nasal congestion repeatedly wakes them. “Sleep duration is merely one of several factors that comprise healthy sleep. One also needs to take into consideration the quality of sleep, the regularity of sleep patterns, timing of sleep, and the restfulness of sleep,” says Dr Karthik, adding that the American Academy of Sleep Medicine recommends that adults get at least seven hours regularly.
Bedtime matters
Sleeping for seven hours at wildly different times each night can disrupt the circadian rhythm. Late-night screen use, caffeine, heavy meals close to bedtime, alcohol, and irregular schedules can further interfere with sleep. Dr Mahadevan V, senior consultant in interventional cardiology and diabetology, Kauvery Hospital, Vadapalani, describes the effect of constantly shifting sleep times as social jet lag. The resulting changes can affect blood pressure and blood sugar control and increase cardiovascular risk. “My simple advice is to fix your bedtime as well as your wake-up time, reduce especially screen time before bed, avoid caffeine at night and avoid meals close to bedtime,” he adds.
Every breath counts
Sleep apnoea deserves particular attention because breathing repeatedly stops or becomes obstructed during sleep. Dr Karthik says these episodes can cause periodic drops in oxygen and repeated arousals, activating the sympathetic nervous system. Loud snoring, witnessed pauses in breathing, choking or gasping during sleep, fragmented sleep, morning headaches and excessive daytime sleepiness can warrant an evaluation.
Not everyone with sleep apnoea is overweight, and not everyone who snores has the condition. Persistent loud snoring combined with breathing pauses or daytime symptoms deserves medical attention. A conference abstract presented at ECO 2026 reported a 71% higher risk of cardiovascular events and all-cause mortality among people diagnosed with obstructive sleep apnoea. Dr Karthik cautions that the analysis was observational, had not undergone peer review, and showed an association rather than proving that obstructive sleep apnoea (OSA) caused those outcomes.
Poor sleep can leave a person tired, irritable and unable to concentrate. Doctors also point to morning headaches, daytime sleepiness, poor exercise tolerance, palpitations and unrefreshing sleep. These symptoms can have many causes, so they should not automatically be blamed on sleep. Chest pain, pressure, breathing difficulty or significant palpitations require medical attention. Dr Mahadevan adds that sleep has become part of his cardiovascular assessment. “Often, that one question opens the conversation, and patients may tell us how they sleep, the quality of sleep and the duration of sleep.” That question matters particularly when a patient has hypertension, diabetes, obesity, cardiovascular disease, or unexplained daytime fatigue.
Given Tamil Nadu's high hypertension and noncommunicable diseases (NCD) burden, Dr Monica says that sleep patterns need to be specifically questioned as part of routine health and risk assessment.
“Patients do not always recognise poor sleep, snoring or daytime fatigue as potential health concerns, and therefore may not bring them up on their own.” Simple questions about sleep duration, regularity, quality, snoring and daytime tiredness can help identify people who may need further evaluation, she adds.
“This is particularly relevant when assessing individuals with hypertension, diabetes, obesity or other metabolic risk factors. Sleep should be considered alongside diet, physical activity, blood pressure, blood sugar and other established factors when discussing long-term cardiovascular health,” concludes Dr Monica.
Consider evaluation when
Nighttime symptoms
Noisy snoring
Pauses in breathing noticed
Choking or gasping while sleeping
Fidgety or interrupted sleep
Awakening from sleep frequently
Excessive sweating while sleeping
Daytime symptoms
Feeling sleepy
Headaches on waking up in the morning
Difficulty concentrating and remembering
Irritable
Persistent tiredness despite enough sleep
