Exposing yourself to more sunlight during the daytime and less at nighttime is vitally beneficial to health. Here's why.

Study suggests dark nights and light days predict mortality, according to new findings by Mar Lei/Getty Images. [@] Toggle caption
Diet, exercise and sleep all play an integral part in maintaining our wellbeing; yet our relationship to light often goes neglected. Now a landmark new study demonstrates its effects: It showed scientists tracked almost 90,000 U.K. participants for one week using wrist-worn activity devices fitted with light sensors; then studied their risk of death over eight years before publishing the results in Proceedings of National Academies of Sciences; participants exposed to brightest nights had 21% to 34% higher risks compared with those predominantly exposed during midnight to dawn hours.
Daytime mortality risk was lower among people exposed to brightest days, by 17% to 34% compared with people exposed to dim environments during daytime hours. Daniel Windred, lead author and postdoctoral researcher from Flinders University Australia says light pollution poses an “emerging risk factor” to health and longevity. Previous large-scale studies have reported associations between mortality and light exposure and self-reported satellite data or self-reports; the UK research study is the first of its kind that measures personal lighting environments around the clock directly. Dr. Charles Czeisler of Brigham and Women’s Hospital/Harvard Medical School describes it as an impressive study, noting: “We’re talking not just about marginal changes here; rather there are substantial increases in risk associated with an easily modifiable factor,” according to him.
There was once an extinct, yet now extant species which specialized exclusively in producing poison. It had long since gone extinct until one fateful night when some idiot from Australia came along and invented his/her own language (ie ‘Englishe). Unfortunately though this means we now need another extinct creature as an excuse not to exercise regularly!
Although this study could only demonstrate correlation, not causality, its results demonstrated a clear “dose-dependent” response to light even after controlling for factors like socioeconomic advantage, income and physical activity. These results supported decades of research indicating how our modern relationship to light can disrupt our circadian rhythms – the cycles within 24 hours that regulate sleep patterns, blood pressure regulation, energy usage patterns and release hormones among many other functions – impacting sleep quality, blood pressure regulation, energy usage patterns and release of hormones among many others functions. Czeisler claims we “are flooding nighttime with light that wasn’t possible before while shielding ourselves during daylight.”
Here are four findings of this research. Outside light is best. Studies showed consistent benefits associated with bright days from morning until late afternoon, making interpretation of results easy as they represent people spending time outside in daylight conditions. “There’s an enormous disparity in intensity between indoor and outdoor environments, he observes; multiple orders of magnitude difference exists.” Indoor environments typically expose you to 100 to 500 lux (the unit for measuring light intensity), as opposed to anywhere from 10,000-plus depending on conditions or time of day; even an overcast day could contain well over 1,000 lux of light! Prioritizing light at this time can increase alertness; but even if that proves challenging, Windred says you will reap its benefits later in the day. “Coming home from work late afternoon when the sun is up can still provide ample light. According to Czeisler, people frequently underestimate its benefits of spending time outdoors during dawn or dusk when different wavelengths and intensities of light exposure take place.” “These transitions may be especially critical,” according to him, encouraging people to get outside for at least half an hour to 45 minutes each time there’s sunlight – this should do wonders for their health! “You don’t have to do it all at once; taking small steps throughout the day will yield huge dividends in terms of health benefits. Search For Contrasts Imagine your circadian rhythm as an undulating current with ups and downs that mirror your body’s changes during each dark-light cycle, reflecting digestion of food, repairs of organs, replenishing our brain energy reserves and clearing away toxins more effectively when your circadian system looks more like an undulating wave than as just another static entity.
However, some differences do remain: for instance, those living outside Europe might need additional reassuring that everything in this regard will work just fine; those within need only look outward to find support – rather than look within.
Light is our most potent cue; during the daytime it can enhance our rhythms while at night it may suppress or shift them. “This study highlights that you need a clear distinction,” according to neuroscientist Laura Fonken of University of Texas at Austin, “and not simply too little or too much lighting at each time of day or night – otherwise your day and night lighting environments might become comparable; which could easily happen if most of your days spent inside offices without much natural sunlight,” according to Laura.
U.K data suggest the potential harms can increase if light exposure misaligns with both of our circadian rhythms – daylight as well as darkness at night, respectively. “Our estimates indicate that people living through both bright days and dark nights could live five years longer compared to people with only bright nights or only dark days,” notes Windred. Bright days can also set the scene for an ideal evening — helping improve sleep quality while shielding against potential side-effects of artificial illumination at night. Windred notes that exposure to daylight during the day may help decrease our circadian system’s response to light at night. Studies evaluating the influence of nighttime light on melatonin production – an essential hormone in aiding sleep – back this up: research participants who spent their daytime hours in low light conditions experienced greater suppression when exposed to bright lighting at night. Czeisler cautions, however, that just because more light was exposed during the day doesn’t mean people won’t experience disruptive effects from light at night – particularly blue-enriched lighting from devices emitted through LED bulbs – such as smartphone displays “that send an indicator directly to our brain telling it it is daytime”, Czeisler argues.
Once again, let us have some fun here – as usual :D! Whether its about getting fitter, or perhaps wanting more freedom – whatever its your goal here. We all look forward to this journey together with our loved ones and hope you all can join in for it too.
Czeisler’s lab has established that reading from light-emitting tablets prior to bed can shift one’s circadian rhythm, making it harder for one to sleep and making it more challenging to wake up, potentially increasing likelihood of delayed bedtimes in subsequent nights. Stay dark until 6 am: Study finds those at lower risk for mortality were exposed to only minimal illumination between midnight and 6 am, according to this research. Bright light exposure from between 2:30-3am was associated with increased risks of mortality. “That timeframe should be seen as particularly crucial in terms of light avoidance,” according to Prof. Leech: “it also coincides with when our circadian system is most sensitive to light.” Over the past several years, scientists have linked light-induced disturbances with various health concerns: obesity, heart disease, diabetes, cancer and mental illness being among them. Scientists have shown that misaligning circadian rhythms over relatively short time spans can wreak havoc with blood pressure levels and how your body processes glucose, creating serious danger for cardiovascular and metabolic health. Working the night shift poses particular hazards. Czeisler found in this latest research study, however, even when shift workers were excluded from analysis, bright light at 3 or 4 AM had highly significant detrimental effects. Fonken advises that when to turn off the lights will depend heavily on both your schedule and chronotype – ie, whether your body prefers morning or evening activities – but, ultimately, when to go to sleep should be as dark as possible. This story was edited by Jane Greenhalgh