How eye sight affects circadian rhythms & other ailments

For decades, scientists have looked for explanations as to why certain conditions occur with age, among them memory loss, s slower reaction time, insomnia & even depression. They’ve scrupulously investigated such suspects as high cholesterol, obesity, heart disease & an inactive lifestyle.

Now research supports largely unrecognized culprit- the ageing of the eye. The gradual yellowing of the lens & the narrowing of the pupil that occur with age disturb the body’s circadian rhythm, contributing to a range of health problems.  As the eyes age, less & less sunlight gets through the lens to reach key cells in the retina that regulate the body’s circadian rhythm, its internal clock.

Circadian rhythms are the cyclical hormonal & physiological processes that rally the body in the morning to tackle the day’s demands & slow it down at night. This internal clock relies on light to function properly & studies have found that people whose circadian rhythms are out of sync, like shift workers, are at greater risk for a no. of ailments, including insomnia, heart disease & cancer.

So-called photoreceptive cells in the retina absorb sunlight & transmit messages to a part of the brain called the suprachiasmatic nucleus, which governs the internal clock. The SCN adjusts the body to the environment by initiating the release of melatonin in the evening & cortisol in the morning. Melatonin is thought to have many health promoting functions & studies have shown that people with low melatonin secretion have a higher incidence of many illnesses.

According to researchers, that by 45, the photoreceptors of the average adult receive 50 % of the light needed to fully stimulate the circadian system. By 55, it dips tp 37 % & by 75 to a mere 17%. Because of these changes, doctors believe that with age, people should make an effort to expose themselves to bright sunlight or bright indoor lighting when they cannot get outdoors. Older adults are at particular risk, because they spend more time indoors.