Purpose Adolescents being in a stage of growth need good sleep, but, today, they suffer from sleep deprivation due to such extrinsic factor as a smartphone which they enjoy spending time using the device. However, the effects of smartphone output power (SOP) on the duration of good sleep remains unclear. The purpose of this paper is to investigate the correlation of the SOP and sleep loss in high school students. Design/methodology/approach The time-series study was conducted among 145 high school students in Chiang Mai Province who completed a sleep diary which applied by the Pittsburg Sleep Quality Index. The SOP was corrected by a smartphone application and transmitted by e-mail to a researcher every day. The completed data set contains 12,969 entries. Headache, anxiety and depression were also assessed. Data were analyzed using the generalized estimating equation adjusted for demographic data, smartphone use and other factors. Findings Most of the study subjects are female, 17.4 years old on average. The prevalence of sleep loss (<8 h) was 52.9 percent with averagely 7.4 ±1.7 h of sleep duration and poor sleep at 32.1 percent. Anxiety, depression, headache had relationships with sleep loss. The daily dose, evening and nocturnal SOP in the range of ≥ 2.00 × 10‒5 mW had stronger relationships with sleep loss than their effects in the range of ≤ 1.79 × 10‒5 mW (ORadj1.32; 95% CI: 1.26–1.76, ORadj1.34; 95% CI: 1.07–1.17 and ORadj1.41; 95% CI: 1.07–1.17, respectively). Meanwhile, morning Lag_2 and daytime Lag_1 in the range of ≥ 2.00 × 10‒5 mW appeared to have a strong relationship with sleep loss (ORadj1.60; 95% CI: 1.26–1.76, ORadj1.36; 95% CI: 1.07–1.17). The relationship between Lag_4 daily dose and sleep loss took the form of a reverse dose-response. Originality/value Sleep loss in adolescents has an increasing trend of prevalence and has been found to be correlated with the highest SOP group (≥ 2.00 × 10‒5 mW range). These results confirmed that increased and longer smartphone use result in reduced sleep time. This causes them to be exposed to smartphone electromagnetic radiation and smartphone screen lighting. This disturbs brain waves and nervous system controlling sleep balance mechanisms. The findings recommended parents setting time and boundaries around technology use at home to reduce contact with electromagnetic radiation and smartphone screen lighting, thereby increasing sleeping time in order to create good sleep quality.

Migraine is one of the most frequent and severe headaches caused by stimulation deep in the brain causing inflammation and pain around nerves and blood vessels in the brain and classified in one group of primary headache by international classification of headache disorders (ICHD) [1]. Previous studies reported light, odor, hunger, weather and smoke as more common triggers of migraine [2]. Migraine is triggered by the stressors which have response mechanism to repeat the stressor of the same kind [3] and increase response to other mediators, manifested as central sensitization. Adolescent most of the time is exposed to various triggers and excessive use of electronic devices that found a risk for ordinary headaches and migraine [4]. Migraine and particularly repeated or recurrent migraine might impose a recognizable burden on the suffers in their adolescence in terms of their impaired health, quality of life and academic performance as well as cause their parent's financial burden in terms of treatment costs [5,6]. A previous study supported comprehensive migraine treatment programs with avoidance of trigger factors through appropriate lifestyle change to reduce headache frequency [2]. The smartphone is manufactured with modernized technology and is popularly used to meet people's various needs. In Thailand, the overall values of the communications market in 2011 grew by 9.2% and the smartphone market was forecasted to increase by 24.9% [7]. Previous studies on the health effects of smartphone use generally reported findings related to headaches (63.2%) [8]. The smartphone output power is an important indicator in assessing electromagnetic energy outside the body related to exposure levels and the amount of energy absorbed in tissues [9]. The smartphone output power was used in real time by software in the smartphone and measuring output power out of smartphone by software or computer program but not measuring individual levels because measurements are taken with the device [10,11]. A smartphone is an electromagnetic emission source closest to the head and the human nerves which are the electrical parts of human body and far from being in a state of equilibrium. Although the emitted electromagnetic energy is below the maximum standard value, it could more or less affect human. Electromagnetic radiation was found to affect the areas of thalamus, raphe magnus nucleus, and spinal cord by reducing the neurotransmitters such as acetylcholine, neuronal

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Purpose Nocturnal headaches among adolescents were reported to be increased with the development of modern technology. The purpose of this paper is to investigate the smartphone electromagnetic radiation related to nocturnal headaches among high school students. Design/methodology/approach The time series study of all 12,969 records from 145 high school students Chiang Mai Province was selected from the population in the first phase by setting criteria. The samples completed a headache diary utilizing a smartphone application. The smartphone output power (SOP) was measured and recorded by the smartphone application and transmitted by e-mail to a researcher. The smartphone use, sleep quality, anxiety and depression also were assessed. Data were analyzed using Generalized Estimating Equation adjusting for demographic data, smartphone use, and sleep quality and otherwise. Findings The resulted showed the prevalence of repeated headaches to be 13.4 percent, nocturnal headache only 5.3 percent and the strongest effect of day time SOP at a 1.80–1.99×10−5 mW range on nocturnal headaches (ORadj5.18; 95% CI: 3.44–7.81). Meanwhile, Lag_6 of daily SOP exposure produced a nocturnal headache effect in a reverse dose-response manner. Furthermore, the nocturnal headache also had the strongest association with age, internet use and device brand (ORadj2.33; 95% CI: 1.08–5.05, ORadj2.14; 95% CI: 1.07–4.2 and ORadj1.68; 95% CI: 1.1–2.4). Originality/value The electromagnetic radiation from a smartphone is the environmental variables influences on headache. The results suggested that there should be limited times for smartphone use and older age to start using a smartphone to prevent headache attacks at night.