- A new study found that when sleep is restricted to 5 hours per night, heart rate and blood pressure worsen over the course of the week in young men.
- Researchers found that attempting to get extra sleep over the 2 nights of the weekend may be insufficient to dial back the hits to an individual’s cardiovascular health.
- Researchers measured participants’ heart rate and blood pressure multiple times throughout the day.
- The participants’ heart rates and systolic blood pressure changed with each day of too little sleep and did not return to baseline by the end of the recovery period.
A third of adults in the United States report getting less than the recommended amount of sleep, according to the Centers for Disease Control and Prevention (CDC).
A new study led by researchers at Penn State suggests that when sleep is restricted during the work week, it may impact an individual’s heart rate and systolic blood pressure.
Additionally, the research suggests attempts to catch up on sleep over the weekend may not be enough to bring back cardiovascular health back to baseline.
The research was published in the journal Psychosomatic Medicine.
An interest in the effects of sleep on cardiovascular health drove David Reichenberger, a graduate student in biobehavioral health at Penn State, to design this study.
For the research, he used data sourced by Dr. Anne-Marie Chang, associate professor of biobehavioral health at Penn State, who had conducted an 11-day inpatient sleep study a few years ago.
For the study, participants went from sleeping up to 10 hours a night to being restricted to 5 hours a night over 5 nights.
“I just really wanted to see what are the effects during this potential work week on someone’s blood pressure and heart rate,” Reichenberger explained to Medical News Today.
Researchers recruited 15 healthy men between the ages of 20 and 35 who lived in Pennsylvania. They excluded participants who had medical or mental health diagnoses, took medicine or drugs, had a recent history of shift work, or had traveled across more than two time zones within the previous three months.
Participants were also excluded if during a screening, they showed risk factors of cardiovascular disease.
Prior to the study, participants met with a psychologist who determined whether they were likely to be able to tolerate 11 days of inpatient study.
For a week before patients came to the Clinical Research Center at Penn State to complete the study they were asked to be in bed from 10 p.m. to 8 a.m. and asked to keep a log of sleep and wake times.
At the research center, participants stayed in private rooms that were sound-dampened with no windows. During scheduled wake periods, participants were not allowed to sit on lay on the bed or to exercise.
Researchers exposed participants to low lighting during wake periods and darkness during sleep opportunities. A dietician designed a menu of weighed foods, which were limited in sodium, that provided three meals a day.
On the first three nights of the study, participants could sleep between 10 p.m. and 8 a.m. On the fourth night, participants could sleep between 12:30 p.m. and 5:30 a.m. This continued for 5 consecutive nights.
“And so this is really simulating an adult’s work week,” Reichenberger told MNT. “They may be self-restricting their sleep, just to go to bed later or get up earlier for work.”
On the final two nights, participants again could sleep between 10 p.m. and 8 a.m.
Approximately every 2 hours during the day, researchers measured the participants’ resting heart rates and blood pressure.
Researchers found that the participants’ heart rate increased by nearly one beat per minute (BPM) with each day of the study.
The average baseline heart rate of participants was 69 BPM. Following the participants’ second night of recovery sleep, the average heart rate of participants was still 78 BPM.
Additionally, researchers found participants’ systolic blood pressure increased by about 0.5 millimeters of mercury (mmHg) per day. The average baseline SBP was 116 mmHg. Following the participants’ second day of recovery sleep, the average SBP was 119.5 mmHg.
Researchers measured no significant impact of sleep on the participants’ diastolic blood pressure.
“We weren’t surprised to find out that sleep restrictions [have] an effect on cardiac outcomes: blood pressure, heart rate,” Dr. Chang, a co-author of the study, told MNT.
“But what surprised me perhaps was that when you allow for recovery sleep […] that the results showed those impairments or increases on the blood pressure and heart rate didn’t return really to baseline level.”
– Dr. Anne-Marie Chang
The researchers believe their study is unique because they measured participants’ heart rate and blood pressure multiple times throughout the day for the duration of the study.
Other studies, Reichenberger told MNT, might take the measurements at a certain time each day or use equipment that takes the measures continuously.
“With more measurements, we have more of an ability to detect whether there’s an effect of the restricted sleep on blood pressure,” he said.
“We can account for the timing of measurements more easily that way. So looking at, let’s say, 8 measurements versus 1 measurement during a day, you can get an indication of how blood pressure and heart rate may change across the day and you can account for that in your statistical analyses,” Reichenberger added.
The researchers noted in their paper that other studies, including one published in PLOS ONE in 2009, measured SBP one time each day and found no increase in SBP during sleep restriction.
Dr. Hani Aiash, a cardiologist and assistant dean of interprofessional research in the College of Health Professions at Upstate Medical University, not involved in this research, pointed out several limitations of the study to MNT.
A key shortcoming of the research, he said, is that the study did not have a control group.
The absence of a control group, the study’s co-authors agree in their paper, challenges their ability “to disentangle the true effects of sleep restriction from effects due to experimental procedures unrelated to cardiac activity.”
Dr. Aiash pointed out that participants who spend nearly 2 weeks living at a laboratory might not behave the same way as they would in their homes.
“If you stay inpatient, [the] first day and second day you will sleep okay,” Dr. Aiash said. “At 11 days, you will feel bored and anxious. Your heart rate will increase. Your blood pressure will increase.”
Another limitation of the study, Dr. Aiash noted, was that all the participants were healthy young men.
Initially, the 11-day inpatient sleep study was conducted to look at the effects of sleep restriction on metabolism. To do this research, Dr. Chang explained to MNT, the researchers elected not to recruit female participants.
“Because the menstrual cycle has an effect on sleep and on [the] cardiometabolic outcome, we wanted to initially just study men,” she said.
In future work, the researchers would like to recruit a mix of men and women as participants in a similar study. They would also like to see if they could replicate their findings with a control group.
Additionally, in future work, the researchers said they would only measure the cardiovascular health of participants instead of taking a wider variety of health measurements.
Reichenberger said he would also like to conduct a similar study that allows participants more than 2 nights to benefit from ample rest.
“We really don’t know how long blood pressure or heart rate is elevated beyond those 2 nights,” he said. “And so it could be that the next day after the study their levels returned to normal or it could be that they remained elevated for another week. We just don’t know.”