Latest Research News
A study examining blood pressure and sleep habits in 323 healthy women found that those who had mild sleep problems were significantly more likely to have elevated blood pressure. Further examination of some of these women revealed an association between endothelial inflammation and mild sleep disturbances. Endothelial inflammation is a significant contributor to cardiovascular disease.
(2018). Effects of Inadequate Sleep on Blood Pressure and Endothelial Inflammation in Women: Findings From the American Heart Association Go Red for Women Strategically Focused Research Network.
Journal of the American Heart Association. 7(12), e008590.
A pilot study involving 14 overweight or obese adults (average age 56) on a calorie-restricted diet, found that those whose diet had higher levels of protein showed greater improvements in their sleep score, regardless of the source of the protein.
In a follow-up study, 44 overweight or obese participants followed a normal-protein or a higher-protein weight loss diet (either 0.8 or 1.5 kg of protein for each kg of body weight) for 16 weeks. Sleep quality improved for those on the high-protein diet, but not for those on the normal-protein diet.
Sleep quality was assessed using the Pittsburgh Sleep Quality Index (PSQI) questionnaire.
The sources of protein were beef and pork, or soy and legume.
Higher protein intake has also been linked to promoting body fat loss, retention of lean body mass and improvements in blood pressure.
Zhou, J., Kim, J. E., Armstrong, C. L., Chen, N., & Campbell, W. W. (2016). Higher-protein diets improve indexes of sleep in energy-restricted overweight and obese adults: results from 2 randomized controlled trials. The American Journal of Clinical Nutrition, 103(3), 766–774. http://doi.org/10.3945/ajcn.115.124669
Stress, including sleep disturbance, is a major contributor to inflammation in the body. Insomnia is associated with increased risk for depression, medical comorbidities, and mortality.
A study involving 123 older adults (55+) with insomnia randomly assigned them to one of 3 types of classes: cognitive behavioral therapy for insomnia, tai chi, or a sleep seminar (the control condition).
Cognitive behavioral therapy for insomnia reduced insomnia symptoms and levels of the inflammation marker C-reactive protein, and reversed activation of molecular inflammatory signaling pathways. These benefits were maintained for 16 months.
Tai chi also reduced inflammation, reducing the expression of inflammation at the cellular level and reversing activation of inflammatory signaling pathways. It marginally reduced levels of C-reactive protein. Again, these benefits were maintained for 16 months.
Those participants assigned to the sleep seminar classes showed no significant changes in inflammatory markers, as expected.
Irwin, M. R., Olmstead, R., Breen, E. C., Witarama, T., Carrillo, C., Sadeghi, N., … Cole, S. (2015). Cognitive Behavioral Therapy and Tai Chi Reverse Cellular and Genomic Markers of Inflammation in Late-Life Insomnia: A Randomized Controlled Trial. Biological Psychiatry, 78(10), 721–729. http://doi.org/10.1016/j.biopsych.2015.01.010
A Finnish study involving 2,570 middle-aged men (42-60) has found that men sleeping less than 6 hours or more than 10 hours suffer from low-grade inflammation (indicated by levels of C-reactive protein) more often than persons sleeping 7-8 hours per night. Additionally, the serum levels of zinc, and the zinc/copper ration, were lowest in those sleeping less than 6 hours, while copper levels were highest in those sleeping more than 10 hours.
It has been suggested that high serum copper concentration is linked to pro-oxidative stress, found in many chronic diseases.
Luojus, M. K., Lehto, S. M., Tolmunen, T., Elomaa, A.-P., & Kauhanen, J. (2015). Serum copper, zinc and high-sensitivity C-reactive protein in short and long sleep duration in ageing men. Journal of Trace Elements in Medicine and Biology, 32, 177–182. http://doi.org/10.1016/j.jtemb.2015.07.008
A small clinical trial involving 49 older adults (average age 66) found that the group who were given a standardized mindfulness meditation program had greater improvement in sleep score than the group given a sleep hygiene education program. They also showed greater improvement on secondary measures of insomnia symptoms, depression symptoms, fatigue interference and fatigue severity. However, differences between the groups were not seen for anxiety, stress or inflammatory signaling, the last of which declined in both groups.
Black DS, O’Reilly GA, Olmstead R, Breen EC, Irwin MR. Mindfulness Meditation and Improvement in Sleep Quality and Daytime Impairment Among Older Adults With Sleep Disturbances: A Randomized Clinical Trial. JAMA Intern Med. 2015;175(4):494-501. doi:10.1001/jamainternmed.2014.8081.
A small study involving 15 adults with moderate-to-severe obstructive sleep apnea and 19 controls with mild or no sleep apnea has found that predicted peak oxygen uptake (VO2), a measure of aerobic physical fitness, was significantly lower in those people with moderate to severe obstructive sleep apnea. Moreover, the number of times a person stopped breathing, for 10-seconds or more, per hour of sleep, predicted 16% of the variability observed in the group's peak VO2.
People who suffer from apnea are more likely to be obese and thus would be expected to be less fit as well, but even compared to people with similar BMI, the apnea patients had a reduced aerobic fitness. It's suggested that the sleep apnea itself causes structural changes in muscle that contributes to exercise problems.
VO2 max measurements may be an early marker for those who are at higher risk of stroke and heart attack
Beitler JR, Awad KM, Bakker JP, Edwards BA, DeYoung P, Djonlagic I, Forman DE, Quan SF, Malhotra A. Obstructive sleep apnea is associated with impaired exercise capacity: a cross-sectional study. J Clin Sleep Med 2014;10(11):1199-1204.
A study involving 302 older women (mean age 82) has found that those with moderate to severe sleep apnea were at twice the risk of having problems in performing basic functions associated with independent living.
Spira, A. P., Stone, K. L., Rebok, G. W., Punjabi, N. M., Redline, S., Ancoli-Israel, S., & Yaffe, K. (2014). Sleep-Disordered Breathing and Functional Decline in Older Women. Journal of the American Geriatrics Society, 62(11), 2040–2046. http://doi.org/10.1111/jgs.13108
A study involving 49 office workers, of whom 27 worked in windowless workplaces and 22 in workplaces with windows, has found that those exposed to natural light slept better, and were also more active.
Employees with windows in the workplace received 173% more white light exposure during work hours and slept an average of 46 minutes more each night.
Workers without windows had lower scores on quality of life measures related to physical problems and vitality, as well as poorer outcomes on measures of overall sleep quality and sleep disturbances.
Boubekri M, Cheung IN, Reid KJ, Wang CH, Zee PC. Impact of windows and daylight exposure on overall health and sleep quality of office workers: a case-control pilot study. J Clin Sleep Med 2014;10(6):603-611.
A very small study, involving eight healthy young men and women, has found that insulin sensitivity gets worse the longer you're awake during the night.
During the study, one group had just five hours of available sleep time each night for five nights before five nights with nine hours of available sleep time. The other group did the opposite, starting with nine hours of available sleep time, followed by five hours per night. Participants were allowed to eat whatever they wanted during the short-night testing period.
The simulated five-day workweek of five hours of sleep per night resulted in a 20% reduced oral and intravenous insulin sensitivity, and it took three consecutive nights of nine hours of available sleep time to restore oral insulin sensitivity to previous levels.
It's worth emphasizing that these were all young and very healthy people.
Eckel, R. H., Depner, C. M., Perreault, L., Markwald, R. R., Smith, M. R., McHill, A. W., … Wright, K. P. (2015). Morning Circadian Misalignment during Short Sleep Duration Impacts Insulin Sensitivity. Current Biology, 25(22), 3004–3010. http://doi.org/10.1016/j.cub.2015.10.011
Sleep apnea is common among overweight and obese individuals, and many people with prediabetes have untreated sleep apnea, although few of them are aware of it.
A study involving 39 middle-aged, overweight or obese volunteers with prediabetes and sleep apnea has found that those who received two weeks of CPAP treatment improved their blood sugar control and the ability of insulin to regulate their blood sugar, and also had lower blood pressure and lower levels of the stress hormone norepinephrine.
Two-thirds of the volunteers received continuous positive airway pressure (CPAP) for eight hours during the night; the other 13 received a placebo to be taken before bedtime. They were told the study would compare the two treatments. All participants slept in the sleep laboratory and were closely monitored.
Sushmita Pamidi, Kristen Wroblewski, Magdalena Stepien, Khalid Sharif-Sidi, Jennifer Kilkus, Harry Whitmore, and Esra Tasali "Eight Hours of Nightly Continuous Positive Airway Pressure Treatment of Obstructive Sleep Apnea Improves Glucose Metabolism in Patients with Prediabetes. A Randomized Controlled Trial", American Journal of Respiratory and Critical Care Medicine, Vol. 192, No. 1 (2015), pp. 96-105. doi: 10.1164/rccm.201408-1564OC
A review of 12 studies involving more than 225,000 people, of whom almost 15,000 had diabetes, has found that shift work carries a 9% higher risk of type 2 diabetes, especially in men and those with rotating shift patterns. Men, in fact, had a 37% greater risk of developing diabetes if they did shift work, while those who did rotating shifts had a 42% higher risk than those who worked a fixed shift pattern.
Gan, Y., Yang, C., Tong, X., Sun, H., Cong, Y., Yin, X., … Lu, Z. (2015). Shift work and diabetes mellitus: a meta-analysis of observational studies. Occupational and Environmental Medicine, 72(1), 72–78. http://doi.org/10.1136/oemed-2014-102150
A Greek study involving 386 middle aged patients (average age 61) with arterial hypertension has found that those who had a midday nap had lower systolic BP than those who didn't. Their average systolic BP readings were 4% lower when they were awake (5 mmHg) and 6% lower while they slept at night (7 mmHg) than non-midday sleepers .
Moreover, midday sleepers had pulse wave velocity levels that were 11% lower and left atrium diameter was 5% smaller — suggesting there is less damage in the arteries and heart. Additionally, midday sleepers had greater dips in blood pressure during the night (which is a good thing), and they took fewer antihypertensive medications.
Longer naps were better than shorter.
The research was presented at the 2015 ESC Congress.
A study involving mice lacking a master clock gene called Bmal1 has found that as the mice aged, their brains showed patterns of damage similar to those seen in Alzheimer's disease and other neurodegenerative disorders. Many of the injuries seemed to be caused by free radicals. Several key antioxidant enzymes, which usually neutralize and help clear free radicals from the brain, have been found to peak in the middle of the day in healthy mice, but not in these mice lacking Bmal1. It may be that, without this daily increase, free radicals remain in the brain longer, causing more damage.
The finding may help explain the connection between sleep problems and Alzheimer’s.
(2013). Circadian clock proteins regulate neuronal redox homeostasis and neurodegeneration.
Journal of Clinical Investigation. 123(12), 5389 - 5400.
An Italian study has found that a significant percentage of Alzheimer’s patients suffer from Obstructive Sleep Apnea Syndrome. This respiratory disorder, which causes people to temporarily stop breathing during their sleep, affects cerebral blood flow, promoting cognitive decline. The finding adds to evidence that detecting and treating OSA early is important for preventing cognitive decline and dementia.
Buratti, L. et al. 2013. Vascular Impairment in Alzheimer’s Disease: The Role of Obstructive Sleep Apnea. Journal of Alzheimer's Disease, 38 (2), 445-53.
Data from 70 older adults (average age 76) in the Baltimore Longitudinal Study of Aging has found that those who reported poorer sleep (shorter sleep duration and lower sleep quality) showed a greater buildup of amyloid-beta plaques.
(2013). Self-reported sleep and β-amyloid deposition in community-dwelling older adults.
JAMA Neurology. 70(12), 1537 - 1543.
A study involving genetically engineered fruit flies adds to our understanding of why sleep and bioclock disruptions are common in those with Alzheimer's disease. People with Alzheimer's often have poor biological rhythms — periods of sleep become shorter and more fragmented, resulting in periods of wakefulness at night and snoozing during the day. It has been thought that Alzheimer’s destroys the biological clock, but this new study indicates that the clock is still working — however, it’s being ignored by other parts of the brain.
(2014). The central molecular clock is robust in the face of behavioural arrhythmia in a Drosophila model of Alzheimer’s disease.
Disease Models & Mechanisms. 7(4), 445 - 458.
A Finnish study involving moderately obese adult patients with mild obstructive sleep apnea (OSA) has found that even a modest weight loss (5%) can improve OSA, if occurring in the early stages of OSA.
A study involving 362 children with reading problems has found that 16 weeks of daily 600 mg supplements of omega-3 DHA from algal sources improved their sleep. According to a sleep questionnaire filled out by parents, 40% of these children had significant sleep problems. Monitoring of 43 of the poor sleepers found that children taking daily supplements of omega-3 had nearly one hour (58 minutes) more sleep and seven fewer waking episodes per night compared with children taking a placebo.
A small trial involving seven older adults with insomnia has found that when they consumed 8 ounces of tart cherry juice twice daily for two weeks, they were able to sleep more than an hour longer each night (averaging 84 minutes) compared to when they took the placebo, and their sleep tended to be more efficient.
Montmorency tart cherries are a natural source of melatonin, a hormone that helps regulate the sleep-wake cycle. The juice also helped to increase the availability of tryptophan, an essential amino acid and a precursor to serotonin that helps with sleep.
A small study involving 18 individuals with at least one mild traumatic brain injury with related sleep disturbance has shown that six weeks of morning bright light therapy resulted in a marked decrease in subjective daytime sleepiness, and improved nighttime sleep.
Sleep, because of its role in brain plasticity, is likely to be important for brain recovery, but unfortunately sleep problems are common in those with TBI.
The research was presented on June 3, in Baltimore, Md., at SLEEP 2013, the 27th annual meeting of the Associated Professional Sleep Societies LLC.
A new study adds to growing evidence of a link between sleep problems and Alzheimer’s. The interesting thing is that this association – between sleep apnea and Alzheimer’s biomarkers — wasn’t revealed until the data was separated out according to BMI.
Those with sleep apnea and a BMI under 25 showed several Alzheimer’s biomarkers (increased levels of tau in the cerebrospinal fluid, greater atrophy of the hippocampus, glucose hypometabolism in regions vulnerable to Alzheimer’s). This (with the exception of glucose hypometabolism in the mediotemporal lobe only) was not found in those with sleep apnea and a higher BMI.
The study involved 68 healthy older adults (average age 71), of whom 18 had normal breathing, 33 mild sleep apnea, and 17 moderate-severe apnea. Those in the latter group tended to have higher BMIs.
Some 10-20% of middle-aged adults in the U.S. have sleep apnea, and this jumps dramatically in those over 65 (30-60%), where the link to obesity is much smaller. The researchers suggest that early preclinical Alzheimer’s damage might be a reason, and plan follow-up research to assess what impact CPAP therapy for sleep apnea has on the Alzheimer’s biomarkers.
Those interested in the relationship between poor sleep and later development of Alzheimer’s might also like to read a Guardian article on the subject.
Osorio, R.S. et al. 2013. Sleep-Disordered Breathing, Aging And Risk For Alzheimer's Disease In Cognitively Normal Subjects. Abstract 38456. Presented at the ATS 2013 International Conference.