Key Insights
As the one‑hour fall time shift approaches this November, a UAB expert highlights the importance of maintaining a stable circadian rhythm and shares practical ways readers can adjust their sleep schedules and lifestyles to support heart health.
Martin Young, Ph.D.Daylight saving time ends this fall on Sunday, Nov. 1, at 2 a.m. local time, pushing the clock back one hour. Although we are granted back one hour of sleep and earlier sunrises, time shifts can result in impacting our bodies both physically and mentally, especially those who may have preexisting medical conditions.
Ongoing research indicates that even small disruptions to the body’s internal clock can influence cardiovascular health, potentially leading to increased heart size, reduced heart function and the development of heart failure.
Even though gaining an hour during the fall time change is linked to an approximate 10 percent decrease in heart attack risk the following Monday morning, as compared with the roughly 10 percent increase seen after the spring shift, the immediate effects on heart health remain prevalent and should not be overlooked.
Martin Young, Ph.D., Distinguished Professor in the University of Alabama at Birmingham Division of Cardiovascular Disease, examines how environmental factors such as the time of day and time shifts can influence cardiovascular health and disease, offering insights and practical tips readers can use to prepare for the upcoming change.
Disruption of circadian rhythm and internal synchronization
The concept of circadian rhythm begins with understanding how life on Earth revolves around a 24-hour light and dark cycle, influencing light availability, temperature, humidity, food access and risk of predators. The externality of Earth’s 24-hour light and dark cycle plays a crucial role in how we internally, biologically synchronize to our environment.
“We have developed biological rhythms to help synchronize us with these environmental cycles, with the most obvious being sleep-wake cycles,” Young said. “Many 24-hour biological rhythms are driven by intracellular circadian clocks, which help to orchestrate the timing of cellular functions.”
The internal 24‑hour clock, or circadian rhythm, coordinates many of the body’s daily functions, often in ways not immediately recognized. The pattern of the body’s circadian rhythm is responsible for controlling functions including rest and wake cycles, regulation of body temperature, digestion and hormone balance. Young says circadian clocks not only assist in synchronizing the body with the environment, but most importantly synchronize internal organs with one another.
“Consider what life would be like if you were one hour out of synchronization with your colleagues, friends or family,” Young said. “You would be late for work, late for picking up your kids from school, late for dinner and so on. Unfortunately, the same is true at a biological level, a loss of temporal synchronization negatively impacts your normal function.”
The value of decreasing sleep disturbances
Young says two major things happen during a one-hour time change. The first is the most widely known: the amount of time we have available for sleep increasing by one hour. Secondly, our circadian clocks eventually reset to the new time of day, which can happen at varying rates. As a result, the organs within the body can become out of synchrony with each other for a couple of days.
A primary suffering that one may experience from a time shift centers around sleepiness and the impaired cognitive function that comes along with fatigue. The failure to regulate one’s sleep during the time change is associated with increased risk of daily incidents such as car accidents or workplace mistakes.
Routine disturbance factors such as traveling through various time zones and sleep apnea should also be taken into consideration for the quantity and quality of one’s sleep. These types of sleep routine disturbances are associated with increased risk both of cardiac events and of cardiovascular disease.
Young says there is a considerable amount of existing evidence indicating that reductions in both sleep quantity and quality can increase risk for various diseases, notably heart disease. Irregular sleep schedules can further throw off the body’s internal clock, making it harder for circadian rhythms to stabilize after the time change and increasing strain on the cardiovascular system.
Young says the general signs of heart attack include:
- Discomfort in the chest or upper body
- Shortness of breath
- Cold sweats
- Nausea
- Lightheadedness
“This evidence is likely due in part to effects on multiple factors that increase risk for heart disease, such as elevation of blood pressure or hypertension, activation of the immune system, elevation of blood glucose and lipids, and enhancement of clotting potential,” Young said. “Together, this can create a ‘perfect storm’ for adverse ischemic events such as heart attacks and stroke.”
If you suspect that you or someone else may be experiencing a heart attack, call 911 immediately.
High-risk individuals and strategic adjustment tips
“In general, shift workers, older adults and individuals with hypertension are at an increased risk of heart disease. One form of cardiovascular disease that can be increased in all three is atherosclerosis,” Young said. “Atherosclerosis is the development of plaques in arteries. Individuals who have preexisting atherosclerosis are particularly vulnerable to heart attacks. Atherosclerosis would therefore make these individuals more vulnerable to the detrimental effects of time change disruption.”
Young says the best strategy to help reduce the detrimental impact of the one-hour time change is to gradually spread that time change over the several days leading up and make small adjustments to one’s schedule to best accommodate how the body will respond to the shift.
The effectiveness of this gradual strategy relies on maintaining a consistent wake and rest time through avoiding staying up late or sleeping in, which may be more difficult to do on the weekends. In preparation for the fall time change, you should wake and rest 15 to 20 minutes later than you typically would around two to three days prior.
“On each of these mornings, be sure to eat breakfast and get a good dose of sunlight, as both of these factors can help resynchronize your circadian clock,” Young said.
Additional strategic steps include limiting light exposure at night, reducing caffeine intake, managing stress to calm the nervous system and increasing daily exposure to natural sunlight.