Daylight Saving Time and Heart Attack Risk | Healos™

• Daylight Saving Time and Your Heart: What the Clock Change Really Does

This Sunday, 1 November 2026, most of Canada and the United States turn the clocks back an hour. For many people it means a welcome extra hour of sleep, followed by darker evenings and a few days of feeling slightly out of sync.

It's a good moment to look at what clock changes do to the heart, because the research is surprisingly clear.

Here is the short answer. Heart attacks rise in the days after the spring clock change, when we lose an hour of sleep, and dip slightly after the fall change, when we gain one. In a Michigan study, heart attacks were about 24% higher on the Monday after the spring shift and about 21% lower on the Tuesday after the fall shift. The lesson is bigger than one weekend: sleep and a steady body clock matter for the heart all year.

简短的答案： 本周日，2026 年 11 月 1 日，加拿大和美国大部分地区会把时钟拨回一小时。对很多人来说，这意味着多睡一小时，随后是更早变黑的傍晚，以及几天的轻微「不同步」。

这是了解调钟对心脏有何影响的好时机，因为研究结论出人意料地清楚：春季调钟（少睡一小时）后的几天心梗增加，秋季调钟（多睡一小时）后略有下降；密歇根一项研究中，春季调钟后的周一心梗约增加 24%，秋季调钟后的周二约减少 21%。启示远不止一个周末：睡眠和稳定的生物钟全年都关系着心脏。

What the studies show

• In Michigan, heart attacks requiring treatment were about 24% higher on the Monday after the spring clock change and about 21% lower on the Tuesday after the fall change, although the total over each week stayed similar (Sandhu et al., Open Heart, 2014).

• In Sweden, heart attacks increased in the first weekdays after the spring transition, with a smaller opposite effect in autumn (Janszky & Ljung, NEJM, 2008).

Researchers think the spring effect comes from losing an hour of sleep and shifting the body clock abruptly, which raises stress hormones and blood pressure in people who are already vulnerable. The fall change, which adds an hour, seems to do the opposite, at least briefly. The clock change doesn't cause heart disease; it may nudge the timing of events in people whose arteries are already at risk.

研究怎么说： 密歇根：春季调钟后的周一，需要治疗的心梗约多 24%；秋季调钟后的周二约少 21%，不过每周总数大致相同（Open Heart 2014）。

瑞典：春季调钟后的头几个工作日心梗增加，秋季则有较小的相反效果（NEJM 2008）。

研究者认为春季效应来自少睡一小时和生物钟的突然改变，这会让本已脆弱的人应激激素和血压升高；增加一小时的秋季调钟似乎作用相反，至少短期如此。调钟本身不会导致心脏病，它可能只是在动脉已有风险的人身上，提前了事件发生的时间。

Your body clock and your heart

The clock-change studies point to something larger: the heart runs on a daily rhythm. Blood pressure, heart rate, stress hormones and the stickiness of platelets all rise in the early morning, which is one reason heart attacks are most frequent between about 6 a.m. and noon (Muller et al., NEJM, 1985).

Short or irregular sleep amplifies that morning surge and, over years, contributes to high blood pressure, insulin resistance and inflammation, the shared root of heart disease (see sleep debt and heart risk). That's why sleep experts, including the American Academy of Sleep Medicine, support ending seasonal clock changes in favour of permanent standard time (Rishi et al., Journal of Clinical Sleep Medicine, 2020).

你的生物钟与心脏： 调钟研究指向一个更大的事实：心脏按日节律运转。血压、心率、应激激素和血小板黏性都在清晨升高，这也是心梗最常发生在约早上 6 点到中午之间的原因之一（NEJM 1985）。

睡眠短或不规律会放大这种清晨高峰，多年下来还会促成高血压、胰岛素抵抗和炎症，也就是心脏病的共同根源。所以包括美国睡眠医学会在内的睡眠专家，都支持取消季节性调钟、改为永久标准时间（2020）。

How to protect your heart at clock-change time

This weekend (fall back):

• Use the extra hour for sleep, not a later night.

• Get morning daylight for 20 to 30 minutes in the first days to reset your clock.

• Keep taking medicines at the same time of day by the new clock; ask your pharmacist if a medicine is time-critical.

• As evenings darken, plan activity earlier and wear visible clothing when walking after dark.

Next March (spring forward):

• Go to bed 15 to 20 minutes earlier for a few nights beforehand.

• Avoid adding extra stress, long drives or heavy meals on the Monday.

• Know the warning signs of a heart attack, and call 911 rather than waiting.

All year: keep a steady wake-up time, aim for seven to nine hours, and ask about sleep apnoea if you snore or wake unrefreshed.

调钟时如何保护心脏： 本周末（拨回一小时）：把多出的一小时用来睡觉，而不是熬夜；头几天每天晒 20–30 分钟晨光，帮助生物钟复位；按新时间在每天同一时刻服药，如有对时间敏感的药物请问药剂师；傍晚变暗后，把活动安排得早一些，天黑后步行穿醒目的衣服。明年三月（拨快一小时）：提前几晚每晚早睡 15–20 分钟；周一避免额外压力、长途驾驶和大餐；了解心梗警示信号，拨打 911 而不是等待。全年：固定起床时间，睡 7–9 小时，打鼾或醒来不解乏要问睡眠呼吸暂停。

Who should pay most attention

Clock changes matter most for people whose hearts are already under strain: after a heart attack, stent or stroke; with heart failure or uncontrolled blood pressure; with sleep apnoea; and for shift workers and people with demanding schedules who already run short on sleep (see overwork and the heart). Note that most of Saskatchewan doesn't change its clocks.

Modern medicine is at its best when it comes to finding problems and saving lives in an emergency. But most heart disease risk builds quietly over the ten or twenty years before the first symptom. That window depends on timely screening, healthy habits kept up over time, and the right preventive care, and steady sleep is one of the simplest.

谁最需要注意： 调钟影响最大的是心脏已承受压力的人：心梗、支架或卒中后；有心衰或血压未控制；有睡眠呼吸暂停；以及本就睡眠不足的轮班工作者和日程繁忙的人。注意：萨斯喀彻温省大部分地区不调钟。

现代医学最擅长的是发现问题和抢救；而心脏病的大部分风险，是在症状出现前的十几、二十年里一点点积累的。那段时间，靠的是及时筛查、坚持优良生活方式，和适当的保健预防——而稳定的睡眠是其中最简单的一项。

How Healos™ supports long-term heart health

Sovereign Monthly · Protect supports the everyday foundations, sleep among them, that protect the heart between check-ups. Each month it provides personalised maintenance nutrition built around four cellular nutrients, adjusted to your health profile and medication list, with regular check-ins on sleep, stress, blood pressure and activity. It renews monthly and can be cancelled any time, or try a single month with no renewal. It's complementary support; it doesn't diagnose, treat or prevent any disease.

Healos™ 如何支持长期心脏健康： Sovereign Monthly · Protect 支持在两次体检之间保护心脏的日常基础，睡眠就是其中之一：每月提供以四种细胞级营养素为核心、按你的健康状况和用药清单调整的个性化维护营养，并定期评估睡眠、压力、血压和活动；按月续费、随时取消，也可先试单月、不续费。它是辅助支持，不诊断、不治疗、不预防任何疾病。

The bottom line

The spring clock change briefly raises heart attack risk; the fall change, this weekend, briefly lowers it. Both remind us that the heart runs on a daily rhythm. Use the extra hour for sleep, get morning light, keep medicines on schedule, and treat steady sleep as part of heart care all year.

结论： 春季调钟会短暂增加心梗风险，本周末的秋季调钟会短暂降低它。两者都提醒我们，心脏按日节律运转。把多出的一小时用来睡觉，晒晒晨光，按时服药，并把稳定的睡眠当作全年心脏照护的一部分。

Frequently asked questions

Does daylight saving time cause heart attacks? It doesn't cause heart disease, but the spring change, when we lose an hour of sleep, has been linked to more heart attacks in the following days: about 24% more on the Monday in one Michigan study.

Is the fall clock change good for your heart? Briefly, it may be. In the same study, heart attacks were about 21% lower on the Tuesday after the fall change, likely because people gain an hour of sleep.

Why are heart attacks more common in the morning? Blood pressure, heart rate, stress hormones and platelet stickiness rise in the early morning, making events most frequent between about 6 a.m. and noon.

How do I adjust to the clock change? Keep a steady wake-up time, get 20 to 30 minutes of morning daylight, take medicines at the same time by the new clock and, before the spring change, go to bed a little earlier for a few nights.

常见问题：

1. 夏令时会导致心梗吗？不会导致心脏病，但春季少睡一小时后的几天心梗增多，密歇根研究中周一约多 24%。

2. 秋季调钟对心脏有好处吗？短期可能有，同一研究中周二约少 21%。

3. 为什么心梗多发生在早晨？清晨血压、心率、应激激素和血小板黏性都升高，约 6 点至中午最常见。

4. 怎么适应调钟？固定起床时间、晒 20–30 分钟晨光、按新时间同一时刻服药，春季调钟前几晚提早睡。

References

1. Sandhu A, Seth M, Gurm HS. Daylight savings time and myocardial infarction. Open Heart. 2014;1:e000019.

2. Janszky I, Ljung R. Shifts to and from daylight saving time and incidence of myocardial infarction. New England Journal of Medicine. 2008;359:1966–1968.

3. Muller JE, et al. Circadian variation in the frequency of onset of acute myocardial infarction. New England Journal of Medicine. 1985;313:1315–1322.

4. Rishi MA, et al. Daylight saving time: an American Academy of Sleep Medicine position statement. Journal of Clinical Sleep Medicine. 2020;16(10):1781–1784.