Studies have consistently shown a strong correlation between sleep deprivation and reduced testosterone levels. Fourth, we recruited only young males in this study since absolute values of saliva testosterone during daytime are different in men and women (higher concentrations in men) due to a distinct metabolism in salivary glands of men and women (Hofman, 2001). Third, to extract information about the physiological response to sleep deprivation and/or blue light, we chose to sample saliva rather than perform multiple blood samplings.
What are some other factors that affect testosterone levels? Blue light disrupts the circadian rhythm, making it harder to fall asleep and achieve deep, restorative sleep. "Night mode" or "blue light filter" settings on smartphones can reduce the amount of blue light emitted by the screen.
Light pollution alters the environmental 24-hour (i.e., diurnal) rhythm of light (i.e., day) and dark (i.e., night) that is dictated by the earth’s diurnal rotation and creates cycles in temperature on land and the sea-surface that can alter sea currents and produce wind in a periodic fashion (Reeves Eyre et al., 2024). Here, we aim to change this perspective by reviewing the physiological and pathophysiological mechanisms by which light exposure alters the intricate hormonal, metabolic and reproductive networks that are relevant to reproductive toxicology. This is despite the reproductive system being intricately linked to metabolism and the circadian system, both of which can be disturbed even by low levels of light. Given that EMR exposure is now almost universal (with billions of mobile devices, Wi-Fi hotspots, and an increasing number of smart home gadgets and IoT devices), any subtle effects on hormones or neurological function could have broad population-wide significance. The FCC has periodically reviewed the scientific evidence and, to date, maintained that current limits protect public health, drawing largely on reports from organizations like the FDA and IEEE that emphasize the lack of definite harm at typical exposure levels. Since then, independent research – including many studies summarized in this report – has indicated that biological effects can occur at levels well below the current safety limits, often via non-thermal mechanisms.
D’ memory performance quantifies participants’ ability to discriminate between new and old items. For the analyses of actigraphy and mood scores, comparisons among the sessions were performed for each sleep parameter using either a paired t test or one-way repeated measures ANOVA, completed by a pairwise comparison post hoc test (Student–Newman–Keuls test). In order to mitigate potential data loss (e.g., exclusion of a participant due to the lack of compliance to our study’s requirements), 17 subjects have been recruited and included in the study. For each trial, participants also reported also their confidence in their responses on a scale from 1 ("not sure at all") to 5 ("absolutely certain"). The first recall session was performed immediately after the exposure session and can be used as a baseline of memory retention.
Shift work schedules were not identified in this cohort, so relationships in day, rotating and night shift workers could not be separated. Although this analysis and publication are recent, the data were from the 2011–14 National Health and Nutrition Examination Survey, and indoor ambient light exposure has increased since then because of greater LED adoption, suggesting the possibility that effects may now be even more pronounced. Diurnal rhythms in both cortisol and testosterone exist, however cortisol’s rhythm is driven largely by the central circadian pacemaker and is circadian in origin, whereas testosterone’s rhythm is in response to the environment and in particular to the timing of sleep (Kelly et al., 2022). On the other hand, melatonin suppression is driven by cone function (with blue being equal to red and green combined) for the first 1–2 h of light exposure, with ipRGCs being dominant over longer duration light exposures and showing a duration dependency (St Hilaire et al., 2022). Recently, it has been recognized that the phase resetting response is maximally sensitive to light in the first several minutes of light exposure, and that this is driven largely by cone function (particularly blue cone function). Microwave radiation from cell phones and wireless devices has been linked in numerous animal studies to lower testosterone levels and impaired sperm function, and some human studies corroborate these hormonal changes with long-term heavy use.
Maintaining a healthy lifestyle is crucial for optimal testosterone production. It’s best to combine night mode with other strategies, such as limiting screen time before bed. This is because the majority of testosterone production occurs during the deeper stages of sleep.
Moreover, recent studies highlighted the direct involvement of pregnenolone on sperm function , suggesting that the impairment of pregnenolone production may have direct consequences on the reproductive health of male shift workers. Furthermore, no significant differences were found in serum cholesterol, triglycerides, and glucose levels between shift workers and daytime workers (Table 1). A total of 88 workers completed the study, of which 46 were daytime workers, and 42 were shift workers. Day workers were required to not have a history of shift work and to have had a routine sleep/wake schedule without sleepless nights for more than 3 weeks prior to the study. A total of 100 participants (50 shift workers and 50 daytime workers) were enrolled among the physicians of the Regional Hospital of Ancona, Italy. The aim of the study was to evaluate the influence of shift work on androgen levels in male shift workers, measuring their total and free testosterone and their precursor pregnenolone.
The experimental design included two 3-day sessions (B,C) performed by all participants in random order. Finally, all assessments were performed post-light administration, and not during the exposure. The participants sat facing a table on which was positioned the light device at a distance of approximatively 60 cm. For lunch, participants received controlled meals consisting of a maximum of 2,500 calories/day with a balanced proportion of nutrients (protein, fat, and carbohydrates). The experimental design included two 3-day sessions that the participants performed in random order (Figure 1).

Gender: Female

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