The Secret to a Long Life
Sunlight. sleeping at night in a pitch dark bedroom, and above all regularity.
Some years ago, I was misquoted, and it went viral. An obscure blog cited “a study by Toronto researcher Dr. Martin Moore-Ede that truck drivers have a 10- to 15-year lower life expectancy than the average American male". Before I knew it, articles were appearing all over the media, and then this quote became a centerpiece of a government policy speech by Anne Ferro, chief of the Federal Motor Carrier Safety Administration, which led to even more requests for media interviews.
This got so bad that I had to issue a statement that I had conducted no such study, and certainly had never made such a statement, and that I am not a Toronto researcher, (Actually I am a former Harvard Medical School professor based in Boston, Massachusetts).
But now, 20 years later, newly published evidence on human longevity and mortality suggests that because of the highly irregular sleep schedule of over-the-road truckload drivers this misquoted statement might very well be true.
Several large-scale studies, some involving over 80,000 people with an average age in their 60’s, recorded how much sunlight each person was exposed to daily, how much light was in their bedroom at night, and how regular was the timing of their sleep. Then, for more than 7 years the researchers tracked how many people died in each group, and from what causes.
The impacts on longevity were enormous:
People who stayed indoors under twilight levels of lighting and rarely ventured outside into bright sunlight died at a 30% greater rate, than those exposed to the most daily sunlight.1 Even though there were more skin cancers, the lengthened lifespan of those exposed to more sunlight overwhelmed any increased skin cancer risk. And the effect of staying indoors and avoiding sunlight was as large as the increased risk of early death in people who smoked.
People who slept with the lights on in their bedroom died at a 30% faster rate, as compared to those who slept in pitch darkness.2 And deaths from cardiovascular (e.g. heart attacks) and metabolic (e.g. diabetes) diseases were increased by 40%.
and the third study3 just published in Sleep (January 2024) showed the biggest effect.
People who sleep at irregular times die much sooner than those sleeping on a regular nightly schedule. Those sleeping on a regular schedule had up to a 48% reduced risk of early death from all causes and up to a 57% lower risk of early death from cardiac and metabolic diseases. Indeed the regularity of sleep had a much bigger effect than how many hours people slept.
It is striking that the highly irregular sleep schedules of over-the-road truckers look very much like those people in the red-labelled chart with the most increased mortality rates.
If you follow all three healthy behaviors (maximize time outdoors, sleep in the dark and follow a precisely regular sleep schedule) will you live forever? Of course not, because there is a lot of overlap between these three behaviors. But they point to the essentials of a healthy lifestyle.
As readers of THE LIGHT DOCTOR will realize the common theme is that all three behaviors lead to robust circadian rhythms tightly entrained to the natural 24 hour day-night cycle
So while we are waiting for the breakthroughs in circadian lighting expected this year. there is much you can do to improve your chances of living a long and healthy life.
Lindqvist PG et al. (2014) Avoidance of sun exposure is a risk factor for all-cause mortality: results from the MISS cohort. J Intern Med 2014; 276: 77–86.
Windred et al (2023). Light at night and modeled circadian disruption predict higher risk of mortality: A prospective study in> 88,000 participants. medRxiv, 2023-09.
Windred DP et al (2024) Sleep regularity is a stronger predictor of mortality risk than sleep duration: A prospective cohort study. SLEEP 47: 1–11 https://doi.org/10.1093/sleep/zsad253