As we age, the quality of the night’s sleep deteriorates to the point that sleeping can become a real ordeal. We have trouble falling asleep, we wake up at the slightest noise, we fight against a certain nighttime anxiety, not to mention the sweats and hot flashes that can consume menopausal women. So many sleep disorders that can have a considerable impact on daily life, as a neurologist explained to us during an interview.
French scientists have looked into these sleep disorders, which affect no less than one in three adults in France. Via a studythe scientific team investigated the biological mechanisms of age-related sleep disorders in order to better understand their origin.
The role of light in biological mechanisms and sleep disorders
In order to develop this study, the Lyon Neuroscience Research Center was interested in circadian rhythm, which is more commonly called the “internal clock” of the human body. This 24-hour cycle governs the majority of biological functions in our body, including the secretion of melatonin. For example, the production of this sleep hormone increases at the end of the day before going to bed, then drops before we wake up. According to previous studies, light blocks the secretion of melatonin, which means that this hormone is mainly released at night. Certain sleep disorders can therefore be explained by this sensitivity to light, causing a desynchronization of the circadian clock.
With this new research, the scientific team wanted to understand the role of the biological mechanism in age-related sleep disorders and how light influences everything. To do this, the researchers observed a group of adults and subjected them to a test. In order to analyze the effects of light on the secretion of melatonin in them, all were exposed to 9 lights of different colors, to identify the mechanisms involved through the photoreceptors involved. The participants were divided into two groups : the first with an average age of 25 years, the second with an average age of 59 years. The experiment was carried out in the middle of the night, so that the body logically releases the most melatonin.
The perception of light changes over the years
Once the experiment was completed, the authors noticed that, in the youngest people, there blue light proved to be very effective to suppress the production of melatonin. In these people exposed to blue light, melanopsin was the sole photoreceptor driving melatonin suppression. Conversely, in older individuals, several photoreceptors, other than melanopsin, contributed to this phenomenon. Among them are the S and M cones, photoreceptors which allow the perception of the world in color.
For scientists, these results suggest that the involvement of melanopsin in visual perception decreases over the years, but nevertheless, the retina compensates for this loss by increasing the sensitivity of other photoreceptors, the involvement of which in the suppression of melatonin was previously unknown. So, this means that the perception of light, like the light needs of individuals, changes with age.
The benefits of daylight for the elderly
For the authors, their results demonstrate that, differently from young people, older people must be exposed to specific light, whose characteristics are those of sunlight. “These results are also of clinical interest, encouraging older people to expose yourself to more daylightricher in wavelengths, rather than artificial light, in order to avoid developing sleep disorders and other alterations such as mood or metabolism disorders…“, commented Claude Gronfier, author and researcher at Inserm, in a press release. Following his momentum, the scientist added that these results offer new perspectives for best personalizing phototherapies and light therapies intended for seniors.
Sources:
- Melatonin suppression by light involves different retinal photoreceptors in young and older adults – Journal of Pineal Research
- Favor natural light to avoid age-related sleep disorders – National Institute of Health and Medical Research (Inserm)