- Screen based devices cause sleep disturbances
- Varied results among researches on the effect of tiny screens on sleep
- Present research concludes sleep pattern not altered by pre-sleep screen exposure
- Daytime lighting maybe a solution to bright screen associated sleep disturbances
Melatonin is a hormone involved in the daily sleep-wake cycle secreted by the pineal gland (generally at night). LED screens affect melatonin secretion and thereby prolongs sleep onset, slow wave sleep and decrease time on rapid eye movement sleep.
‘Using your laptop, computer, mobiles or other screen-based technologies just before going to bed could make you feel less rested and disturb your normal sleep pattern. However a recent study shows that the quality of sleep does not differ post usage of such devices.’
Short Wavelength Enriched Screen Exposure - Is It Really Deleterious?12 individuals were subjected to evening use of tablet computers for 5 consecutive days which showed that there is a late shift in pre-sleep melatonin increase, increased sleep onset latency, decreased time in REM sleep and increased tiredness and sleepiness in the morning.
However, contradictory results are seen in other similar studies. For example a comparative study done between people using short wavelength enriched screen containing tablet and tablets with short wavelength filter concluded that there was no significant difference in the sleep pattern.
In another similar study on reading with iPad before sleep gave a comparable result, it also showed that sleepiness before turning off the lights and early night slow-wave activity is reduced. This made the path for further research to check on the age old fact about short wavelength enriched screens.
The present experimental research was conducted in Uppsala Biomedical centre, Sweden and was published in Sleep Medicine journal. 14-right handed adults with normal eye sight, with no prior medical or psychiatry illnesses, who have the habit of sleeping between 21.00 and 23.00 and waking up between 06.00 and 10.00 with a good 7-9hrs sleep were enrolled in the study.
Prior to reading they were exposed to 6.5hrs of normal room light conditions following which polysomnography was attached to them at 20.00 and reading exercise was started at 21.15 under a reading lamp. Saliva melatonin measurements were taken serially from 21.00 hrs, every half hour for 2hrs lights were switched off at 23.15 for sleep. Participants sleepiness were rated using Karolinska Sleepiness Scale (KSS). Melatonin levels were measured using commercially available immunoassay.
During sleep, electroencephalogram and electrooculogram were used to monitor the sleep pattern and measure the sleep onset latency, total sleep time, latency of slow-wave sleep and time in each stage for sleep. Two participants could not be included in the analysis of sleep due to technical issues.
LED Screen Usage Before Sleep Does Not Affect Nocturnal SleepThe results of this study were little contrary to what was traditionally thought of about LED screen usage before sleep. There was no difference in the baseline melatonin levels and the circadian rhythm of melatonin secretion (melatonin secretion and sleep increases as the evening progresses) between the two reading techniques.
Regarding personal experience all the individuals gave similar feedback of book reading and e-book reading on a tablet. The evening tablet use did not affect the sleep onset, sleep duration, or time spent in the different sleep stages and also time of slow wave sleep latency, in contrast to the earlier studies.
"One plausible explanation for these discrepant results across experiments, in our view, is that bright light exposure during daytime similar to that employed in the present study has previously been shown to attenuate the suppressive properties of evening light exposure on melatonin levels," said lead study author Frida Rangtell, a neuroscience researcher at Uppsala University in Sweden.
The subjective ratings of sleep by each individual on the basis of time taken to fall asleep, sleep quality and morning sleepiness did not differ between the two reading conditions i.e. evening tablet reading did not affect the quality of sleep.
The main difference between the present study and the previous study was the duration and timing of evening light stimulus with screen based devices. This could make a difference in the melatonin levels and quality of sleep in both the studies as the extent of blue light exposure plays a major role in this physiology.
Some limitations in the study were the small sample size, the used bright light conditions are different from the normal indoor light, short duration of exposure to screen based devices and the fact that the previous light exposure was not taken into consideration.
"As most of us know, reading on tablets, checking emails on phones, or watching late night TV are a chronic issue, and unfortunately become part of our pre-sleep habits," said Karatsoreos, a neuroscience researcher in Washington state university( not part of the research team). This study seems to evaluate only short term single exposure to bright light, further research is needed to study the effect of this common ritual of regular continuous exposure.
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