BACKGROUND: In response to growing concerns about the health effects of quasi-millimeter waves (qMMW) used in 5th-generation wireless systems, conservative whole-body exposure thresholds based on indirect evidence have been proposed. The guidelines define a whole-body average specific absorption rate (WBA-SAR) of 4 W/kg which causes a 1 °C increase in core temperature, as the operational threshold for adverse health effects. To address the lack of direct evidence, we recently reported that a 30-minute exposure to qMMW at 4.6 W/kg resulted in a 1 °C increase in rat core temperature. Here, we further analyzed the near-threshold stress response for the first time, using biological samples from the aforementioned and additional experiments. METHODS: A total of 59 young Sprague-Dawley rats (240-322 g) were exposed to 28 GHz for 40 minutes at WBA-SARs of 0, 3.7, and 7.2 W/kg, under normal (22.5 °C, 45-55% humidity), and heat (32 °C, 70% humidity) conditions. Rats were restrained in acrylic holders for dose control. We repeatedly measured serum and urinary biomarkers of stress response, aggregated the data, and analyzed them using a single statistical mixed model to subtract the effects of sham exposure and between-subject variation. RESULTS: Sham exposure induced stress responses, suggesting an effect of restraint. After the subtraction of the sham exposure effect, 28 GHz appeared to induce stress responses as evidenced by elevated serum-free corticosterone 1 or 3 days after the exposure, which was more evident in animals with a change in rectal temperature exceeding 1 °C. Urinary-free catecholamines demonstrated an inhibitory property of 28 GHz frequency exposure on the stress response as evidenced by noradrenaline on the day of exposure. Heat exposure enhanced this effect, suggesting a possible role of noradrenaline in heat dissipation by promoting cutaneous blood flow, a notion supported by the correlation between noradrenaline levels and tail surface temperature, a critical organ for heat dissipation. CONCLUSIONS This study is the first to demonstrate that qMMW whole-body exposure can alter the stress response as indicated by corticosterone and noradrenaline at near-threshold levels. Our findings may provide insight into the biological basis of the whole-body exposure thresholds in the international guidelines.
Animals ; Rats ; Rats, Sprague-Dawley ; Male ; Restraint, Physical ; Stress, Physiological/radiation effects* ; Corticosterone/blood* ; Biomarkers/blood* ; Microwaves/adverse effects*

BACKGROUND: Our previous observational cohort study, the Kashima Scan Study (KSS), identified associations between lifestyle, cerebral small vessel disease (SVD) as detected by magnetic resonance imaging of the brain, and disease outcomes including cognitive impairment and vascular diseases. However, established modifiers of the outcomes such as genetic background, drinking and exercise habits, and socioeconomic status were not considered. Regarding genetic factors in particular, the ALDH2 rs671 variant, East Asian-specific diversity, and APOE status are expected to have strong effects. The aim of KSS-2 is to examine the interactions of genetic background, lifestyle factors including drinking habit, socioeconomic status, and/or SVD markers for cognitive impairment, vascular disease, and death. METHOD: The KSS-2 is a prospective regional observational study of a healthy Japanese cohort that will clarify lifestyle habits to better maintain brain health from midlife by genotype. Japanese adults who underwent brain health checkups at their own expense are enrolled and will be followed-up for 10 years. We will extend the protocol of the KSS to include genetic background and potential confounding factors, including lifestyle (including drinking and exercise habit) and socioeconomic status, and perform survival analyses. The study outcomes are cognitive impairment, vascular events, and death. RESULTS: We enrolled 908 healthy adults (mean age 64.2 years; range 35 to 84 years; 41% male) from September 1, 2018 until December 31, 2024. CONCLUSION This study will provide important insights into the development of individualized health intervention strategies.
Adult ; Aged ; Aged, 80 and over ; Female ; Humans ; Male ; Middle Aged ; Cerebral Small Vessel Diseases/diagnostic imaging* ; Japan/epidemiology* ; Life Style ; Magnetic Resonance Imaging ; Prospective Studies ; Observational Studies as Topic

BACKGROUND: Difficulty awakening is a common concern among adolescents and contributes to school absenteeism. Although cross-sectional studies suggest that commuting times, internet usage, and sleep disturbances are associated with school attendance problems, few have specifically focused on adolescents. We aimed to examine the factors contributing to school absenteeism due to difficulty awakening in Japanese high school students. METHODS: In this longitudinal cohort study, data were prospectively collected between 2016 and 2018 from 54 high schools in a prefecture of Western Japan. Tenth-grade students (n = 6,121) without tardiness (n = 5,812) or absences (n = 5,946) at baseline were recruited. The outcome of interest was school absenteeism due to difficulty awakening, which included both tardiness and absences (≥2 days/month). Cox proportional hazards models were used to assess the associations between commuting time and lifestyle factors after adjusting for confounders. RESULTS: The incidence rates of tardiness and absences due to difficulty awakening were 19.3 and 9.6 per 1,000 person-years, respectively. Common risk factors for absenteeism included prolonged internet usage (≥5 h) and dissatisfaction with school. Protective factors for school tardiness included study time and participation in extracurricular sports activities (both ≥2 h). Long commuting time (≥1 h) was associated with a higher risk of school absences. CONCLUSIONS Long commuting times, prolonged internet usage, and poor school satisfaction increased the risk of school absenteeism due to difficulty awakening. Promoting academic engagement and extracurricular activities may help reduce absenteeism. Interventions that increase school satisfaction, such as providing learning opportunities outside of school, supporting extracurricular activities, and improving the school environment, may be effective prevention strategies.
Humans ; Absenteeism ; Japan/epidemiology* ; Adolescent ; Male ; Female ; Prospective Studies ; Schools/statistics & numerical data* ; Students/psychology* ; Longitudinal Studies ; Risk Factors ; Transportation/statistics & numerical data* ; East Asian People