This TED Talk about sunlight exposure and heart health is fascinating:

https://www.ted.com/talks/richard_weller_could_the_sun_be_go...

I completely agree that more research isolating sunlight exposure as an independent variable would be interesting. I live in Poland, where we effectively have about 2-3 months of warm, sunny summer with long days. I generally go for long walks throughout the year, thanks to the natural surroundings here—beautiful forests and the sea.

I've noticed a significant shift in my mood during June, July, and August, which aligns with those sunny days. My mood changes from "okay" to "fantastic," and I've been tracking this shift year over year. The combination of physical activity and sunlight exposure certainly seems to have an "amplifier effect" on overall well-being.

I can't wait to see cultural uptake of the importance of light and circadian friendly indoor lighting.

Of course, I'd prefer advances in construction that would allow large amounts of full spectrum light to enter buildings, but that's only relevant to new construction.

Not a direct comparison, but the data on using a light box has good research support (independent of exercise). Light has a significant effect on mood.