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Wallace DA. Light Exposure Differs by Gender in the US: Women Have Less Bright Light Exposure than Men. MEDRXIV : THE PREPRINT SERVER FOR HEALTH SCIENCES 2024:2024.04.28.24306495. [PMID: 38746463 PMCID: PMC11092728 DOI: 10.1101/2024.04.28.24306495] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2024]
Abstract
Light is a salient environmental exposure, serving as the primary entraining cue for the circadian system and having other, non-circadian, effects on health. Gender differences in light exposure patterns could contribute to gender differences in health outcomes and would have important implications for sleep and circadian research. Gender differences in real-world light exposure (measured over a week with wrist-worn ActiGraph GT3X+ devices) were investigated in cross- sectional data from the 2011-2014 National Health and Nutrition Examination Survey (NHANES). Measures of time above light threshold (TALT), individual photoperiod (IP), first and last timing of light (FTL and LTL, respectively), and mean light timing revised (MLiTR) at different light intensity thresholds were derived. Gender differences in light exposure were tested using two-sample t-tests, Watson's two-sample test of homogeneity, and linear regression models. Exploratory analyses to investigate work and physical activity-related factors in relation to bright light exposure were also conducted. A total of 11,318 NHANES participants (age range: 3-80+, 52.2% women) with 6 days of valid actigraphy and light data were included in the analysis. The findings suggest that for every 60 minutes of bright light (≥1,000 lux) that men receive, women receive 39.6 minutes. Men spend approximately 52% more time in bright light than women and this gender difference begins in childhood. The IP of bright light exposure is also longer for men, with earlier first and later last timing of bright light exposure compared to women. These gender differences were robust across ages and between race and ethnicity groups. While further research is needed, these gender differences in light exposure may be due to gender differences in indoor vs. outdoor activities. Future studies of gender differences in response to light exposure should consider light exposure history in study design and analysis. The results of this study may inform future health disparities research and support the importance of the study of light as an important environmental exposure and component of the human exposome.
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Bragazzi NL, Boulares A, Garbarino S. Could the Historical Transition from Segmented to Monophasic Sleep Explain the Modern Insurgence of Alzheimer's Disease and Related Dementias? J Alzheimers Dis 2024; 98:1283-1286. [PMID: 38578895 DOI: 10.3233/jad-240154] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/07/2024]
Abstract
In their article, Finch and Burstein explore the hypothesis that Alzheimer's disease and related dementias (ADRD) may predominantly be phenomena of the modern era. Through a review of classical Greek and Latin literature, they found minimal reference to conditions akin to ADRD, suggesting a historical rarity of severe cognitive decline. Instead, ancient texts focused on physical aspects of aging, with cognitive changes, when noted, not resembling modern-day dementia. Finch and Burstein further extend their analysis by drawing parallels with the Tsimane people of Bolivia, known for their low prevalence of dementia and cardiovascular diseases, attributed to lifestyle factors such as diet and physical activity. By comparing historical sleep patterns transitioning from segmented to monophasic sleep with those of the Tsimane community, we enriched Finch and Burstein's research, highlighting the need to take into account a range of diverse factors, including sleep, in understanding the etiopathogenesis of ADRD in today's society.
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Affiliation(s)
- Nicola Luigi Bragazzi
- Department of Mathematics and Statistics, Laboratory for Industrial and Applied Mathematics (LIAM), York University, Toronto, ON, Canada
- Department of Food and Drugs, Human Nutrition Unit (HNU), University of Parma, Parma, Italy
- Department of Health Sciences (DISSAL), Postgraduate School of Public Health, University of Genoa, Genoa, Italy
- United Nations Educational, Scientific and Cultural Organization (UNESCO) Chair, Health Anthropology Biosphere and Healing Systems, University of Genoa, Genoa, Italy
| | - Ayoub Boulares
- Faculty of Sport Sciences-STAPS, Laboratory Mobility, Aging and Exercise-ER20296, University of Poitiers, Poitiers, France
| | - Sergio Garbarino
- Department of Neuroscience, Rehabilitation, Ophthalmology, Genetics and Maternal/Child Sciences (DINOGMI), University of Genoa, Genoa, Italy
- Post-Graduate School of Occupational Health, Università Cattolica del Sacro Cuore, Rome, Italy
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Schöllhorn I, Stefani O, Blume C, Cajochen C. Seasonal Variation in the Responsiveness of the Melanopsin System to Evening Light: Why We Should Report Season When Collecting Data in Human Sleep and Circadian Studies. Clocks Sleep 2023; 5:651-666. [PMID: 37987395 PMCID: PMC10660855 DOI: 10.3390/clockssleep5040044] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2023] [Revised: 09/07/2023] [Accepted: 10/09/2023] [Indexed: 11/22/2023] Open
Abstract
It is well known that variations in light exposure during the day affect light sensitivity in the evening. More daylight reduces sensitivity, and less daylight increases it. On average days, we spend less time outdoors in winter and receive far less light than in summer. Therefore, it could be relevant when collecting research data on the non-image forming (NIF) effects of light on circadian rhythms and sleep. In fact, studies conducted only in winter may result in more pronounced NIF effects than in summer. Here, we systematically collected information on the extent to which studies on the NIF effects of evening light include information on season and/or light history. We found that more studies were conducted in winter than in summer and that reporting when a study was conducted or measuring individual light history is not currently a standard in sleep and circadian research. In addition, we sought to evaluate seasonal variations in a previously published dataset of 72 participants investigating circadian and sleep effects of evening light exposure in a laboratory protocol where daytime light history was not controlled. In this study, we selectively modulated melanopic irradiance at four different light levels (<90 lx). Here, we aimed to retrospectively evaluate seasonal variations in the responsiveness of the melanopsin system by combining all data sets in an exploratory manner. Our analyses suggest that light sensitivity is indeed reduced in summer compared to winter. Thus, to increase the reproducibility of NIF effects on sleep and circadian measures, we recommend an assessment of the light history and encourage standardization of reporting guidelines on the seasonal distribution of measurements.
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Affiliation(s)
- Isabel Schöllhorn
- Centre for Chronobiology, Psychiatric Hospital of the University of Basel, 4002 Basel, Switzerland; (I.S.); (O.S.)
- Research Cluster Molecular and Cognitive Neurosciences (MCN), University of Basel, 4001 Basel, Switzerland
| | - Oliver Stefani
- Centre for Chronobiology, Psychiatric Hospital of the University of Basel, 4002 Basel, Switzerland; (I.S.); (O.S.)
- Research Cluster Molecular and Cognitive Neurosciences (MCN), University of Basel, 4001 Basel, Switzerland
- Lucerne University of Applied Sciences and Arts, Engineering and Architecture, Technikumstrasse 21, 6048 Horw, Switzerland
| | - Christine Blume
- Centre for Chronobiology, Psychiatric Hospital of the University of Basel, 4002 Basel, Switzerland; (I.S.); (O.S.)
- Research Cluster Molecular and Cognitive Neurosciences (MCN), University of Basel, 4001 Basel, Switzerland
- Department of Biomedicine, University of Basel, 4001 Basel, Switzerland
| | - Christian Cajochen
- Centre for Chronobiology, Psychiatric Hospital of the University of Basel, 4002 Basel, Switzerland; (I.S.); (O.S.)
- Research Cluster Molecular and Cognitive Neurosciences (MCN), University of Basel, 4001 Basel, Switzerland
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Seasonal Changes in Sleep Patterns in Two Saskatchewan First Nation Communities. Clocks Sleep 2021; 3:415-428. [PMID: 34449570 PMCID: PMC8395418 DOI: 10.3390/clockssleep3030029] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2021] [Revised: 08/04/2021] [Accepted: 08/06/2021] [Indexed: 11/24/2022] Open
Abstract
Sleep is crucial for maintaining the recovery and restoration of the body and brain. Less sleep is associated with poor mental and physical performance. Seasonal changes in sleep patterns can be observed. This paper examines seasonal effects on sleep timing, duration, and problems in two Cree First Nation communities in Saskatchewan, Canada. Data were available from a community survey of 588 adults aged 18 years and older (range: 18–78 years) with 44.2% males and 55.8% females. Results are presented using descriptive statistics and a binary logistic-regression model to identify the association between seasonal changes in sleep patterns, and demographic, social, and environmental factors. The participants reported sleeping the least during the spring and summer months and sleeping the most during the fall and winter months. This was further confirmed by sleep hours and the lower proportion of recommended hours of sleep during the spring and summer, and a higher proportion of longer sleep duration during the fall and winter months. There was no significant variation in sleeping onset and wake-up times by season. Overall, there were no significant differences in the prevalence of sleep deprivation, insomnia, and excessive daytime sleepiness by season. When stratified by age group and sex, some differences existed in the prevalence of sleep problems by season. More than two-thirds (68.6%) of the participants reported that there was a change in sleep patterns across seasons, and about 26.0% reported a very or extremely marked change in sleep patterns across seasons. Changes in sleep patterns by season were related to money left at the end of the month and damage caused by dampness in the house.
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Weaver MD, Sletten TL, Foster RG, Gozal D, Klerman EB, Rajaratnam SMW, Roenneberg T, Takahashi JS, Turek FW, Vitiello MV, Young MW, Czeisler CA. Adverse impact of polyphasic sleep patterns in humans: Report of the National Sleep Foundation sleep timing and variability consensus panel. Sleep Health 2021; 7:293-302. [PMID: 33795195 DOI: 10.1016/j.sleh.2021.02.009] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2020] [Revised: 02/25/2021] [Accepted: 02/26/2021] [Indexed: 01/02/2023]
Abstract
Polyphasic sleep is the practice of distributing multiple short sleep episodes across the 24-hour day rather than having one major and possibly a minor ("nap") sleep episode each day. While the prevalence of polyphasic sleep is unknown, anecdotal reports suggest attempts to follow this practice are common, particularly among young adults. Polyphasic-sleep advocates claim to thrive on as little as 2 hours of total sleep per day. However, significant concerns have been raised that polyphasic sleep schedules can result in health and safety consequences. We reviewed the literature to identify the impact of polyphasic sleep schedules (excluding nap or siesta schedules) on health, safety, and performance outcomes. Of 40,672 potentially relevant publications, with 2,023 selected for full-text review, 22 relevant papers were retained. We found no evidence supporting benefits from following polyphasic sleep schedules. Based on the current evidence, the consensus opinion is that polyphasic sleep schedules, and the sleep deficiency inherent in those schedules, are associated with a variety of adverse physical health, mental health, and performance outcomes. Striving to adopt a schedule that significantly reduces the amount of sleep per 24 hours and/or fragments sleep into multiple episodes throughout the 24-hour day is not recommended.
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Affiliation(s)
- Matthew D Weaver
- Division of Sleep and Circadian Disorders, Departments of Medicine and Neurology, Brigham and Women's Hospital, Boston, Massachusetts, USA; Division of Sleep Medicine, Harvard Medical School, Boston, Massachusetts, USA
| | - Tracey L Sletten
- Turner Institute for Brain and Mental Health and School of Psychological Sciences, Monash University, Clayton, Australia
| | - Russell G Foster
- Sleep & Circadian Neuroscience Institute, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
| | - David Gozal
- Department of Child Health, University of Missouri, Columbia, Missouri, USA
| | - Elizabeth B Klerman
- Division of Sleep and Circadian Disorders, Departments of Medicine and Neurology, Brigham and Women's Hospital, Boston, Massachusetts, USA; Division of Sleep Medicine, Harvard Medical School, Boston, Massachusetts, USA; Department of Neurology, Massachusetts General Hospital, Boston, Massachusetts, USA
| | - Shantha M W Rajaratnam
- Division of Sleep and Circadian Disorders, Departments of Medicine and Neurology, Brigham and Women's Hospital, Boston, Massachusetts, USA; Division of Sleep Medicine, Harvard Medical School, Boston, Massachusetts, USA; Turner Institute for Brain and Mental Health and School of Psychological Sciences, Monash University, Clayton, Australia
| | - Till Roenneberg
- Institute for Medical Psychology, Ludwig Maximilian University of Munich, Munich, Germany
| | - Joseph S Takahashi
- Department of Neuroscience, The University of Texas Southwestern Medical Center, Dallas, Texas, USA; Howard Hughes Medical Institute, The University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Fred W Turek
- Center for Sleep and Circadian Biology, Department of Neurobiology, Northwestern University, Evanston, Illinois, USA
| | - Michael V Vitiello
- Department of Psychiatry and Behavioral Sciences, University of Washington, Seattle, Washington, USA
| | - Michael W Young
- Laboratory of Genetics, The Rockefeller University, New York, New York, USA
| | - Charles A Czeisler
- Division of Sleep and Circadian Disorders, Departments of Medicine and Neurology, Brigham and Women's Hospital, Boston, Massachusetts, USA; Division of Sleep Medicine, Harvard Medical School, Boston, Massachusetts, USA.
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