Sleep-cycle researcher: Modern urban environments expose people to artificial light after sunset, which disrupts the body's circadian rhythm. Before widespread electrification, melatonin release rose shortly after dusk, promoting earlier sleep onset and deeper sleep cycles. Today, bright indoor lighting and screen exposure delay melatonin production, particularly where light intensity is high close to bedtime. In a recent study, researchers observed participants who kept their room lights on before attempting to sleep. Some participants sat under those lights for a short time before going to bed and others for several hours, and the researchers recorded how long it then took each participant's melatonin level to rise far enough to induce natural sleep. The study therefore showed that as the ______1______ increased, the ______2______ increased.
Select for 1 and for 2 the phrases that create the statement that most logically completes the passage.
Make only two selections, one in each column.
