What percentage of your waking hours do you spend outside? If you’re like most Americans, upwards of 90% of your time is spent indoors. We go from our homes to our cars to work, and maybe get in a short walk during lunch or after dinner. Are you outside even a full hour each day? What about in winter?
Humans have made our interior spaces ever more comfortable and interesting – with climate control and exploding opportunities for online entertainment – but all that comfort may come at a cost.
While you may have heard about the benefits of spending time outside, you may not have given much thought to the flip side, the health issues stemming from so much time indoors.
Humans evolved in nature, hunting, gathering and farming. It’s only in the last few centuries that our species has largely shifted to spending the vast majority of our time inside. As industrialization freed us from needing to use most of our waking hours searching for or growing food, it increasingly contained us within the walls of homes and offices.
This trend has accelerated markedly in the last two decades. With the rapid increase in entertainment and work opportunities available to us through the magic of technology, we’re spending more time than ever inside. Researchers are just beginning to explore the health impacts of lives now led primarily indoors.
The Health Risks of Indoor Living
Here’s how all that time inside may be affecting our health.
We’re starving our bodies of natural light
If you thought sun exposure was all about vitamin D, you might be surprised to learn that popping a vitamin D supplement – while possibly helpful for supporting health in other ways during the shorter days of winter – doesn’t provide the same benefits as actually going outside during daylight hours. The benefits of sunlight extend far beyond vitamin D.
Probably the most profound impact on our health resulting from our indoor lives comes from the drastic reduction in our exposure to natural light. Human physiology evolved outside, and our circadian rhythms rely on cues that come from the sun.
During the day, if we don’t get exposure to sunlight, our circadian clocks struggle to get the stimulation they need to regulate our sleep/wake cycle. Even a well-lit room or one with ample windows provides only a small fraction of the light we receive sitting in shade outdoors. A very brightly-lit office, for example, may have a light level of around 500 lux, while even on a cloudy day outside levels can be closer to 15,000, and a clear day may reach 130,000.
Further, when we use devices and lights with a lot of blue in them at night, we send signals to the brain that it’s actually daytime, suppressing the production of melatonin, a hormone that regulates not only sleep, but also energy metabolism.
The result? Sleep disturbances, metabolic issues and all the health problems that arise from disruptions to the ways our bodies are designed to function.
Without the appropriate light cues needed to regulate our sleep/wake cycles, our circadian rhythms are disrupted, affecting the release of hormones that regulate everything from sleep and hunger to mood, metabolism and reproductive cycles. Circadian disruptions have been linked to metabolic disorders, cardiovascular disease and increased cancer risk.
LED light may negatively impact mitrochondria
Mounting research suggests that a vital issue to consider is not simply the amount of light we’re receiving, but the types of light. In the last 20 years, our pursuit of energy-efficient lighting has led to a dramatic shift in our indoor lighting environment, and researchers believe it’s taking a serious toll on our health.
Glen Jeffery, a Professor of Neuroscience at University College London, believes that the LED lighting that dominates in modern buildings is posing a significant threat to public health. “The extremely restricted spectral range of light emitting diodes is increasingly problematic,” he says, because of the “total absence of infrared light in LEDs.”
According to Jeffery, light emitted by LED bulbs tends to fall exactly in the range that have very damaging effects on our mitochondria. “Our mitochondria,” he explains, “evolved in a broad spectrum of light,” and they depend on wavelengths at the far end of the spectrum – which efficient bulbs don’t emit – in order to function properly.
Combined with modern windows designed to block infrared light and the limited amount of time most people spend outdoors, the amount of full spectrum light exposure modern humans receive isn’t sufficient to support health, Jeffery asserts.
Deprived of the full spectrum of light, he says, our mitochondrial function suffers. “There are walls of evidence LEDs are damaging,” he notes. “If you keep insects under these blue wavelengths, they die.”
Humans don’t fare well, either, Jeffery says. “We now know that infrared light is significant in terms of our healthspan and a whole range of conditions.”
Architects and doctors are taking notice of these findings and are working to correct this imbalance, including in hospital settings, where sunlight exposure is sometimes being prescribed for critical care patients, with encouraging results.
Less sun exposure linked to decreased longevity
Sunlight’s effect on our health doesn’t end with our eyes. What happens when it hits our skin may also play an important role in supporting health.
While dermatologists have long advocated for sun avoidance, emerging research is casting doubt on the wisdom of this longstanding advice.
Richard Weller, a professor of dermatology at the University of Edinburgh, has called for a rethinking of the guidance dermatologists have given about sun avoidance in recent decades. He points out that a very small number of people die from skin cancer each year, while research suggests that the health problems caused by insufficient exposure to sunlight are a far greater concern to public health.
A longitudinal study of nearly 30,000 Swedish women found that all-cause mortality in participants who reported avoiding sun exposure was double of those who said they actively sought out sun. Study authors reported that non-smokers who avoided sun exposure had similar all-cause mortality rates to smokers who got ample sun exposure. Surprisingly, rates of death from skin cancer were higher in those who avoided sun exposure.
A study published in late 2024 analyzing nearly 400,000 UK residents found that “UV exposures were inversely associated with all-cause, cardiovascular disease (CVD) and cancer mortality.” Even participants who reported using tanning beds had reduced mortality risk. These findings, the authors write, “add to growing evidence that the benefits of UV exposure on mortality outweigh the risks in low sunlight environments.”
Weller speculates that sun exposure’s protective effect may derive from the production of nitric oxide on our skin when exposed to sunlight. Research has found nitric oxide dilates blood vessels, thereby lowering blood pressure and lessening the risk of cardiovascular disease and stroke, two leading causes of death in developed countries. Additional factors, such as better circadian function, contact with nature, and more physical activity, likely play a role as well.
Contact with nature supports wellbeing
In addition to the ways different elements of sunlight affect how our bodies’ function, numerous studies have found that time spent in natural environments has a positive impact on health. The health benefits of nature include lower blood pressure, decreased levels of stress hormones and greater feelings of wellbeing.
Research has revealed that time spent in nature increases feelings of physical and mental energy. Even exercising in natural environments appears to have benefits over performing the same activity indoors. One study found that people walking through natural environments “showed reduced neural activity in an area of the brain linked to risk for mental illness compared with those who walked through an urban environment.”
A number of studies have found that forest bathing – the Japanese practice of mindfully taking in the sights, sounds, smells, and feelings of the forest – may have exceptional power to lower cortisol and blood pressure while improving mood.
Even mundane garden chores can provide health benefits. According to a 2020 study, people who tend gardens “reported better health and wellbeing, more physical activity and more nature visits than those who did not.”
Time indoors and soaring rates of myopia
One emerging effect of our indoor lives is the increasing rate of myopia in children. In some parts of Asia, up to 80% of children are now nearsighted. Interestingly, in places with a culture that prioritizes time outdoors, rates are far lower. One study compared ethnically similar children living in Singapore and Australia, where kids routinely spend several hours outdoors every day. While the cohort living in Singapore had an 80% rate of myopia, their Australian counterparts had rates below 30%.
Interestingly, research in Norway has found surprisingly low rates of myopia, despite the lower amounts of daylight during fall and winter. Researchers hypothesize that the outdoor-focused culture in Norway has played a critical role in protecting Norwegian children from the increasing rates of myopia seen in other developed countries.
Karla Zadnik, a professor of Optometry and Physiological Optics at The Ohio State University, led a longitudinal study of school-aged children and found that kids who spent more time outdoors were less likely to develop nearsightedness. Studies from around the world support these findings.
Though we don’t have definitive data on exactly how much outdoors time is optimal for protecting children’s eyesight, Zadnik says, studies on the links between time outdoors and myopia “seem to be landing on about two hours a day.” That’s considerably more, she points out, than most kids get during a typical elementary school recess.
While two hours is worth striving for, Zadnik notes that falling short of this goal doesn’t mean it isn’t worth trying to get kids outside more often. “It’s not as if anything less than that is worthless,” she says. Any extra time kids spend outdoors may help protect their eyesight, along with the many other benefits outlined above.
Zadnik says that sunglasses don’t interfere with the beneficial effect of outdoor light, and if you want to promote long-term eye health, protecting your eyes from UV radiation is a good idea. “There’s evidence that sun exposure without sunglasses might be a contributing factor to the development of cataracts.”
We’re breathing more polluted air
You’ve likely heard that indoor air tends to be far more polluted than the air outside. Chemical pollutants emitted from furnishings, gas stoves and cleaning products can make indoor air up to five times more polluted than the air outside, according to the EPA.
As construction practices emphasize better sealing of buildings to conserve energy, problems have arisen with trapping pollutants indoors. Even the carbon dioxide we emit when we exhale can build up in well-sealed structures, which can cause headaches and decreases in cognitive performance.
We tend to move less indoors
Spending time inside often means sitting on a chair or sofa rather than moving around. It’s well established most of us don’t get enough exercise, which in addition to long-term effects on our metabolism and risk of cardiovascular disease, in the short term can increase chronic pain and compound sleep issues.
Couple all this sitting with being constantly tethered to electronic devices, and the toll on our posture can be significant. Poor posture in turn further increases pain and saps our energy, and can even promote negative thinking and depression.
How to counter the health effects of time spent indoors
First and foremost, make an effort to spend more time outside, whether it’s taking a morning stroll or having your lunch at a park instead of an indoor restaurant. Let the treadmill or stationary bike gather dust when the weather’s nice and get out for a jog or a ride instead.
Consider enjoying your morning coffee out on a deck or balcony if that’s an option, as morning sun exposure is thought to be exceptionally helpful for regulating your circadian rhythm. If you work from home, try taking your laptop outside when you can to get a dose of extra sunlight without compromising productivity.
If you live somewhere with severe winters, time outside might prove more challenging much of the year. But make a point of getting out as much as you can all year round, and take advantage of the warmer months to spend more of each day outdoors.
For the time you do spend indoors, consider ways to make it more conducive to better health:
Manage your light environment
Pay attention to the type and amount of light in your home. That means adding red wavelengths where you can, spending time by windows, and reducing light exposure – especially to blue light – after sunset. Jeffery recommends using halogen bulbs, which have the broadest spectrum of light, with a dimmer switch so you can lessen the amount of energy used.
Prioritize air quality
Ventilate as much as you can, and invest in quality air filters. Avoid chemical cleaners and air fresheners, and if you have a gas stove, be sure to use a range hood that vents to the outside. If your home is tightly sealed, consult with an HVAC specialist about adding an air-to-air exchanger to allow in fresh air without compromising efficiency.
Move more
Don’t let being inside mean being sedentary. Take frequent movement breaks and consider using a walking desk.
Add plants
Those benefits of nature can be brought indoors to some extent. Houseplants can help to filter indoor air pollution, and some studies suggest they can reduce stress and boost creativity and feelings of well-being.
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