(If they’re incandescent bulbs, take them out and throw them away.)
The proliferation of artificial light, via the humble light bulb, could be seriously harming us all by messing with our circadian rhythms.
Once humans began to use artificial light to vary the length of the day, the average night’s sleep decreased from about nine hours to about seven, and the amount of sleep began to vary considerably from one night to the next. This irregularity prevents one’s circadian rhythm from settling into a pattern, and creates a state of perpetual semi-jet-lag. Our bodies’ rhythms attempt to appropriately adjust our alertness, blood pressure, and such for particular times of day; but we often do things contrary to this cycle, and therein lies the problem.