A good night’s sleep is one of those precious commodities that is often difficult to obtain in our hectic, modern lives. Between work and family, not to mention binge watching your favorite series, getting enough sleep each day can be challenging. We stay up too late, we rise too early, and often we don’t sleep well while in bed. Fatigue and poor productivity are common results of our poor sleep habits, but a trio of new reports suggest even more serious health issues are related to insufficient sleep. In a large Chinese study , nearly 500,000 adult individuals with no known heart disease were evaluated for sleep patterns and cardiovascular issues over nearly a decade. Three types of sleep issues were identified: trouble falling asleep (TFA), waking too early (WTE), and daytime fatigue (DTF) because of disrupted sleep. Individuals with all three sleep issues were 18% more likely to develop cardiovascular disease than persons with no sleep issues. Even individuals with any one of the three sleep issues had higher incidences of cardiovascular disease: TFA, 9% higher; WTE, 7% higher; and DTF, 13% higher. Such studies are intriguing, but don’t establish causation, simply a correlation. For example, there could be another factor that causes both sleep issues and the cardiovascular disease risk. It will be important to determine if addressing sleep issues helps to prevent this increased cardiovascular disease risk.
The second study, published in the Journal of Bone and Mineral Research, examined sleep and bone mineral density (BMD) in 11,084 post-menopausal women. BMD was determined for the whole body, the hips, the neck, and the spine, while sleep duration information was collected with a questionnaire. Women who reported sleeping 5 hours or less per night on average had statistically lower BMD at all sites and greater odds of having osteoporosis of the hips and whole body. As for the cardiovascular study, this bone study is just correlative as both poor sleep and lower BMD may be caused by some other underlying factor. However, it is known that inadequate sleep does increase inflammation and can affect hormone levels, both factors that could be affecting BMD. Again, it will be critical to determine if improving sleep improves BMD and reduces osteoporosis risk.
The final study, in Nature Human Behavior, examined the basis for the known correlation between sleep loss and anxiety. In an initial laboratory experiment with volunteers, this study confirmed that even one night of sleep deprivation significantly raised anxiety scores in the participants. To get at the cause of this sleep effect the brains of the volunteers were examined by functional MRI (fMRI). In these follow up experiments they showed that lack of sleep reduces activity in the medial prefrontal cortex, a region of the brain known to regulate anxiety. Reduced sleep also stimulates activity in the brain’s emotional center which increases anxiety. These negative effects were counteracted by deep sleep (non-rapid eye movement sleep- NREM), emphasizing the importance of sleeping long enough to ensure sufficient NREM sleep each night for good mental health. Collectively, these three studies illustrate the importance of sleep on heart, mind, and body, so if today’s blog made you sleepy, maybe that’s not such a bad thing!