HEALTHY LIGHT EXPOSURE IS THE OBVIOUS SOLUTION Mccarthy,

Considerable debate surrounds daylight saving time and how to manage seasonal changes in light. In the last five years, at least 19 states (including California) have enacted legislation or passed resolutions to stop changing clocks, and the U.S. Senate voted to support permanent daylight saving time.

Proponents cite the hassle of clock changes and say permanent daylight saving time will simplify timekeeping by eliminating annual “fall back” and “spring forward” cycles. With a special blend of populism and wishful thinking, they promise that permanent daylight saving time will keep us on a schedule that favors extended afternoon daylight all year round.

On the other hand, scientific experts strongly oppose permanent daylight saving time, pointing out it will reduce time asleep and interfere with our daily, 24-hour circadian rhythms.

Most sleep experts argue permanent standard time is the better and healthier option. Others see benefits in keeping the status quo or argue that the transition from winter to summer time could be kept, but made smoother and more attuned to human biology. Currently, the political momentum rests with permanent daylight saving time, but this would be a mistake for our health and society.

The “spring forward” change to daylight saving time has the same effect on our bodies as jet lag from a flight one time zone to the east, with its one-hour advance in activity and sleep time.

Unfortunately, our brain clocks and bodies lag behind, causing disruptions in physiology including digestive and endocrine systems, and in sleep-wake cycles. During daylight saving time transition,

people may have blood sugar spikes or indigestion. They may be inattentive, moody or irritable, leading to more accidents and heart attacks.

After a few days, additional evening light delays the release of the hormone melatonin, and shifts circadian rhythms to adjust to the new schedule. The immediate impact of these effects may be brief, subsiding after a few days. But living on daylight saving time for months has longer-lasting negative effects on circadian rhythms and sleep, which are more detrimental and the real problem with daylight saving time.

Full spectrum, outdoor light is much brighter and more active on the brain than indoor light. Under permanent daylight saving time, extended darkness and lack of outdoor light on winter mornings would negatively affect circadian rhythms. In northern regions of California, winter sunrise would not happen until almost 9 a.m., well past the start of the work and school day.

This would greatly reduce exposure to morning sunlight — the most powerful environmental signal to set circadian rhythms in the brain. Low levels of outdoor light exposure have been linked by research to depression, anxiety and insomnia. Chronobiologists predict permanent daylight saving time would have adverse effects on health and productivity, and point out it would undo any benefits of recent reforms around delaying school start times.

In the summer months, daylight saving time has additional ill effects on sleep. In San Diego, the difference in sunlight between a December day and June day is about five hours. Since bright light is a powerful trigger to wake up, many people arise earlier in summer than they do during winter.

Daylight saving time makes the already long summer days go an hour later and causes people to postpone essential sleep. Since summer sunrise times are earlier, the net effect is that sleep is pinched at both ends and people generally sleep much less during daylight saving time.

For a nation that is already sleep deprived, this is not healthy.

While lawmakers focus on the inconvenience around clock changes, lack of light and longterm sleep loss are bigger concerns from a health and science standpoint. Permanent daylight saving time seems popular with the public. In an age of public skepticism and distrust of institutions, scientists must avoid promoting solutions, even evidence-based ones, that are too far out of touch with popular sentiment. After all, scientists enjoy summer barbecues too.

The solution must be one that recognizes the irrefutable biology around sleep and light restriction, while noting legitimate concerns regarding inconvenience and the perceived societal benefits of daylight saving time.

Our current system is based on Industrial Revolution technology. It’s easier — and possible — now to imagine a system that conveniently makes incremental changes to time over the seasons to optimize light exposure, convenience and health using automatically adjusting clocks.

Let’s think more innovatively about how to make healthy light exposure the simple and obvious option for society.