A new study has found that losing as little as one hour of sleep a night is associated with higher blood pressure in pre-teens and teenagers. Frequent or ongoing sleep loss, which can result in higher blood pressure, could put sleep-deprived youths at greater risk for cardiovascular disease in later years.
Researchers from the Chinese University of Hong Kong recruited 143 children ages 10 to 18, who had participated in an earlier study on sleep apnea. The participants were healthy, neither overweight nor obese, and they did not have sleep apnea. (Sleep apnea is a condition characterized by interrupted or shallow breathing when a person is sleeping; the disorder has been linked to higher blood pressure.)
The children were asked to fill out sleep diaries for seven days before they were to enter a 24-hour sleep lab, where researchers measured the subjects’ blood pressure, sleep duration and quality of sleep. Study participants reported in their diaries that they had been sleeping anywhere from 7 hours or less a night, to 10 or more hours before entering the lab.
Children who had had the least amount of sleep during the preceding week were generally found to have slightly higher blood pressure than those who had slept more. Each hour of nightly sleep lost was associated with an increase of 2 mm Hg (2 millimeters of mercury) for systolic blood pressure, the upper number, and an increase of 1 mm Hg for diastolic blood pressure, the lower number.
The mechanisms by which insufficient sleep may affect blood pressure are still being investigated; but for starters, scientists know from past studies that children who don’t get a full night’s sleep wake up with higher cortisol levels in their blood.
Cortisol is the primary human stress hormone; it has many important metabolic and regulatory functions in our bodies, and it also increases vessel sensitivity to the hormones epinephrine and norepinephrine, which cause veins to contract (thus increasing blood pressure). But long-term excessive cortisol in the blood, such as that caused by chronic stress, can produce many bad outcomes, including weakened immune function and impaired memory.
Researchers in the Chinese study found that subjects who had lost the most sleep during the week had tended to go to bed later and wake up earlier. But during the 24-hour sleep lab, these same children — the most sleep-deprived — went to sleep the earliest and slept the most hours.
This led the research team to speculate that it is possible to catch up on lost sleep and thus reap sleep’s healing properties. However, they noted that the blood pressure increases that were associated with ongoing sleep loss were only partially undone by “catching up” on some lost sleep. Even when sleep-deprived children spent additional hours sleeping, their blood pressures were still higher than those of children who generally got more sleep. While blood pressure numbers were most closely associated with the child’s sleep the night before, the “carryover” effect of preceding nights of lost sleep, or the “sleep debt,” remained measurable.
The best thing for a growing child, then, is to always aim to get a good night’s sleep. The way to do this is by maintaining a similar routine, even on weekends. Parents should also be vigilant that their children aren’t staying up late, whether to read, study, use electronic media, and so forth.
Parents should talk to their children about the importance of getting enough sleep for their overall health. If electronics are proving too much of a draw for your child at bedtime, for instance, it may be time for tougher measures, such as removing the devices (TV’s, laptops, cell phones, etc.) from the child’s room — or setting strict sleep-time guidelines, making sure that you have explained to your child how not getting enough sleep will affect their health, now and later. It will be much easier to gain compliance from your child if they have a clear understanding that they stand to gain much more by valuing and guarding their sleep time every night than by pushing their bedtime to surf the net, text friends or read that suspense novel.
Children 5 to 12 years old need 10-11 hours of sleep a night; teenagers need about 9 hours. Total silence and darkness promote the most restful sleep for all of us, no matter our age.
(Findings of the above study were published online in December and are appearing in the January, 2014 print issue of the journal
By Jamell Andrews