How we perceive the normal ebb and flow of the day is called our circadian rhythm. This rhythm includes when we feel tired and sleepy at the end of the day. As we grow older, our sleep pattern changes. Teenagers tend to stay up longer and older patients perceive bedtime earlier.
The cause for these differences that occur with age may be related to how we appreciate the amount of light during the evening. Normally, when the sunlight wains our brain tells us that bedtime is near. When we approach sunset out brain will begin to produce melatonin which makes us tired and encourages sleep. Older patients, particularly those with vision issues such as cataracts may not get enough light signals to the brain and as far as the brain is concerned night is approaching. For some patients the connections in the brain that tell us it is time to sleep may not be functioning well which further complicates the urge to sleep.
The bottom line is that one of the factors making older patients feel sleepy sooner is the lack of light stimulation. Think about how you feel when we “turn the clocks back” each year. The sun sets at 4 to 5 pm and most of us will start to feel sleepy around that time.
Light stimulation is not the only circadian factor in making us sleepy but it is an important one. Other cues include when we generally eat our evening meal which signals bedtime is near.