The human biological rhythms are strongly affected by light exposure. We measured light exposure levels continiously in big samples, and we try to reveal how much, what color, what timing of light people are exposed to in modern society. Importantly, we scientifically analyze the relationship between light exposure and various health data and desease incidence. In the future, we will proceed with further analysis and clarify how to be exposed to light to prevent diseases.

• Related articles

  1. Obayashi K, Tai Y, Yamagami Y, Saeki K. Associations between Indoor Light Pollution and Unhealthy Outcomes in 2,947 Adults: Cross-Sectional Analysis in the HEIJO-KYO Cohort. Environ Res, 215 114350, Dec, 2022. 2. Obayashi K, Yamagami Y, Tatsumi S, Kurumatani N, Saeki K. Indoor Light Pollution and Progression of Carotid Atherosclerosis: A Longitudinal Study of the HEIJO-KYO Cohort. Environ Int, 133 105184, Dec, 2019. 3. Obayashi K, Saeki K, Kurumatani N. Bedroom Light Exposure at Night and the Incidence of Depressive Symptoms: A Longitudinal Study of the HEIJO-KYO Cohort. Am J Epidemiol, 187(3) 427-434, Mar, 2018. 4. Obayashi K, Saeki K, Kurumatani N. Ambient Light Exposure and Changes in Obesity Parameters: A Longitudinal Study of the HEIJO-KYO Cohort. J Clin Endocrinol Metab, 101(9) 3539-3547, Sep, 2016. 5. Obayashi K, Saeki K, Iwamoto J, Okamoto N, Tomioka K, Nezu S, Ikada Y, Kurumatani N. Positive Effect of Daylight Exposure on Nocturnal Urinary Melatonin Excretion in the Elderly: A Cross-sectional Analysis of the HEIJO-KYO Study. J Clin Endocrinol Metab, 97(11) 4166-4173, Nov, 2012.

Melatonin is a hormone secreted by the pineal gland at night, and is deeply involved in regulating biological rhythms and sleep. When exposed to light at night, melatonin secretion is suppressed, causing disturbances in biological rhythms and sleep disorders. Melatonin is known to have various physiological effects, such as lowering blood pressure, suppressing carcinogenesis, antioxidant, tranquilizing, and stimulating the immune system, but there are currently few large-scale studies. Our research team has measured the urinary metabolites of melatonin in more than 3,000 adults and is studying their relationship with health data and disease development.

• Related articles

  1. Obayashi K, Saeki K, Iwamoto J, Tone N, Tanaka K, Kataoka H, Morikawa M, Kurumatani N. Physiological Levels of Melatonin Relate to Cognitive Function and Depressive Symptoms: The HEIJO-KYO Cohort . J Clin Endocrinol Metab, 100(8) 3090-3096, Aug, 2015. 2. Obayashi K, Saeki K, Kurumatani N. Higher Melatonin Secretion is Associated with Lower Leukocyte and Platelet Counts in the General Elderly Population: The HEIJO-KYO Cohort. J Pineal Res, 58(2) 227-233, Feb, 2015. 3. Obayashi K, Saeki K, Kurumatani N. Association between Urinary 6-sulfatoxymelatonin Excretion and Arterial Stiffness in the General Elderly Population: The HEIJO-KYO Cohort. J Clin Endocrinol Metab, 99(9) 3233-3239, Sep, 2014.

Sleep is full of many mysteries, but recent advances in sleep research have revealed a wide variety of things. Several wearable devices are developed that can easily and objectively measure sleep quality. Our research team measures objective sleep indices in large populations and studies their association with health data and disease development. More than half of the elderly suffer from sleep problems. It is very important to find new risk factors for sleep disorders, and we believe that our data will provide basic information for new treatment methods.

• Related articles

  1. Kataoka H, Saeki K, Yamagami Y, Sugie K, Obayashi K. Quantitative Associations between Objective Sleep Measures and Early-Morning Mobility in Parkinson’s Disease: Cross-Sectional Analysis of the PHASE Study. SLEEP, 43(1), Jan, 2020. 2. Oume M, Obayashi K, Asai Y, Ogura M, Takeuchi K, Tai Y, Kurumatani N, Saeki K. Objective Sleep Quality and Nighttime Blood Pressure in the General Elderly Population: A Cross-Sectional Study of the HEIJO-KYO Cohort. J Hypertens, 36(3) 601-607, Mar, 2018. 3. Obayashi K, Kurumatani N, Saeki K. Gender Differences in the Relationships between Chronic Kidney Disease, Asymmetric Dimethylarginine, and Sleep Quality:The HEIJO-KYO Cohort. Nitric Oxide, 79(9) 25-30, Sep, 2018.

With aging, the number of times you go to the bathroom at night increases. Nearly half of the elderly suffer from nocturia, which involves going to the toilet more than once at night, and it is essential to identify the new risk factors and know the health effects. Our research team has obtained large-scale data on nocturnal urine volume and nocturnal void frequency, and has reported new findings so far. We are continuing our research with the goal of reducing as many people as possible who suffer from nocturia.

• Related articles

  1. Obayashi K, Saeki K, Kurumatani N. Association between Melatonin Secretion and Nocturia in Elderly Individuals: A Cross-Sectional Study of the HEIJO-KYO Cohort. J Urol, 191(6) 1816-1821, Jun, 2014. 2. Obayashi K, Saeki K, Negoro H, Kurumatani N. Nocturia Increases the Incidence of Depressive Symptoms: A Longitudinal Study of the HEIJO-KYO Cohort. BJU Int, 120(2) 280-285, Aug, 2017. 3. Obayashi K, Saeki K, Kurumatani N. Quantitative Association between Nocturnal Void Frequency and Objective Sleep Quality in the General Elderly Population: The HEIJO-KYO Cohort. Sleep Med, 16(5) 577-582, May, 2015.

As a co-researcher, I'm involved in many other studies besides "light," "melatonin," "sleep," and "nocturia."

・Data science of temperature environment (Dr. Keigo Saeki, Nara Medical University School of Medicine)
・Data science of skin temperature (Dr. Yoshiaki Tai, Nara Medical University School of Medicine)
・Data science of noise environment and physical activity (Dr. Yuki Yamagami, Nara Medical University School of Medicine)
・Data science of Parkinson's disease (Dr. Hiroshi Kataoka, Nara Medical University School of Medicine)
・Data science of glaucoma and cataract (Dr. Masanobu Yoshikawa, Nara Medical University School of Medicine)
・Data science of bipolar disorder (Dr. Yuichi Ezaki, Fujita Health University School of Medicine)
・Data science of hospital room environment (Dr. Junko Iwamoto, Nara Medical University School of Medicine)

In these studies, large-scale data on environmental factors and biological information are acquired, and the relationship with disease onset and disease stage progression is studied.

• Related articles

  1. Yamagami Y, Obayashi K, Tai Y, Saeki K. Association between Indoor Noise Level at Night and Objective/Subjective Sleep Quality in the Older Population: A Cross-Sectional Study of the HEIJO-KYO Cohort. SLEEP, (in press), Aug, 2022. 2. Saeki K, Obayashi K, Iwamoto J, Tanaka Y, Tanaka N, Takata S, Kubo H, Okamoto N, Tomioka K, Kurumatani N. Influence of Room Heating on Ambulatory Blood Pressure in Winter: A Randomised Controlled Study. J Epidemiol Community Health, 67(6) 484-490, Jun, 2013. 3. Tai Y, Obayashi K, Yamagami Y, Saeki K. Inverse Association of Skin Temperature with Ambulatory Blood Pressure and the Mediation of Skin Temperature in Blood Pressure Responses to Ambient Temperature. Hypertension, 79(8) 1845-1855, Aug, 2022. 4. Obayashi K, Saeki K, Yamagami Y, Kurumatani N, Sugie K, Kataoka H. Circadian Activity Rhythm in Parkinson's Disease: Findings from the PHASE Study. Sleep Med, 85(9) 8-14, Sep, 2021. 5. Nishi T, Saeki K, Miyata K, Yoshikawa T, Ueda T, Kurumatani N, Obayashi K, Ogata N. Effects of Cataract Surgery on Melatonin Secretion in Adults 60 Years and Older: A Randomized Clinical Trial. JAMA Ophthalmol., 138(4) 405-411, Apr, 2020. 6. Yoshikawa T, Obayashi K, Miyata K, Saeki K, Ogata N. Increased Nighttime Blood Pressure in Patients with Glaucoma: Cross-Sectional Analysis of the LIGHT Study. Ophthalmology, 126(10) 1366-1371, Oct, 2019. 7. Esaki Y, Obayashi K, Saeki K, Fujita K, Iwata N, Kitajima T. Association between Circadian Activity Rhythms and Mood Episode Relapse in Bipolar Disorder: A 12-month Prospective Cohort Study. Transl Psychiatry, 11(1) 525, Oct, 2021. 8. Iwamoto J, Saeki K, Kobayashi M, Yamagami Y, Yoshida O, Kurumatani N, Obayashi K. Lower Incidence of In-Hospital Falls in Patients Hospitalised in Window Beds than Non-Window Beds. J Am Med Dir Assoc, 21(4) 476-480, Apr, 2020.