Irregular Sleep Cycle: A Shortcut to Heart Disease

An irregular sleep-wake cycle can affect your heart health and increase the risk of heart attacks and strokes, even in those who get the recommended amount of sleep each night, finds a new study published in the Journal of Epidemiology & Community Health ().

Most studies looking at the impact of sleep on health have focused on sleep length and less is known about the impact of sleep patterns, in particular the impact of irregular sleep-defined as variations in the time a person goes to sleep and wakes up.

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Irregular sleepers face a 26% greater risk of heart disease compared to regular sleepers. #IrregularSleep #heartdisease #medindia’

Impact of Irregular Sleep on Heart Health

To explore this further, the researchers drew on 72,269 people aged 40 to 79, taking part in the UK Biobank study, none of whom had any history of major cardiovascular events.

They wore an activity tracker for 7 days to record their sleep, the data from which were used to calculate each person's Sleep Regularity Index (SRI) score.

People with an SRI score of more than 87 were considered to have a regular sleep pattern, while those with an SRI score of less than 72 were categorized as irregular sleepers. And those whose scores fell between this range were regarded as moderately irregular sleepers.

Incidents of cardiovascular death, heart attack, heart failure, and stroke over the next 8 years were collected from death registries and hospital records and used to calculate the risk of these events for each sleep pattern group.

Irregular Sleep-Wake Cycles: The Silent Trigger for Heart Disease

After accounting for a range of potentially influential factors, such as age, physical activity levels, discretionary screen time, fruit, vegetable, and coffee intake, alcohol consumption, smoking, mental health issues, medication use, and shift work, irregular sleepers were 26% more likely to have a major cardiovascular event than those with a regular sleep wake-cycle, while moderately irregular sleepers were 8% more likely to do so.

More detailed analysis of the data showed that the relationship between decreasing SRI score and higher risk of events was almost linear, with a steeper reduction in risk at higher (better) SRI scores.

The recommended amount of nightly sleep is 7 to 9 hours for 18 to 64 year olds and 7 to 8 hours for those aged 65 and above. A greater proportion of regular sleepers met the recommended sleep quota than irregular sleepers: 61% vs 48%.

But when the impact of clocking up the recommended sleep quota was taken into account, the risk of a major cardiovascular event wasn't offset in irregular sleepers who achieved this, although it was in moderately irregular sleepers.

This is an observational study, and as such, can't establish cause and effect, and the researchers acknowledge various imitations to their findings.

While the study's sample size was large, the UK Biobank may not accurately reflect the UK population. Sleep patterns were also assessed during a single week only. The activity tracker didn't distinguish between quiet wakefulness and sleep, and the sleep algorithm used to calculate SRI scores didn't take napping into account, only the longest period of sleep.

But the researchers nevertheless conclude that the findings suggest that irregular sleep is strongly associated with a risk of major adverse cardiovascular events in adults, irrespective of whether or not recommended sleep quotas are met.

Consistent Sleep, Stronger Heart

"More importantly, our results suggest that sleep regularity may be more relevant than sufficient sleep duration in modulating MACE [major adverse cardiovascular event] risk," they say.

They add: "Findings from this study suggest that more attention needs to be paid to sleep regularity in public health guidelines and clinical practice due to its potential role in cardiovascular health."

So, let's sleep well to live well.

References:

1. Sleep regularity and major adverse cardiovascular events: a device-based prospective study in 72 269 UK adults - (https:jech.bmj.com/content/early/2024/10/30/jech-2024-222795)

Source: Eurekalert