Wednesday, December 5, 2007
Sunlight may save kids' sight
Exposure to sunlight may boost kids' dopamine levels, which reduces their chances of myopia, scientists say
Exposure to sunlight could be a critical factor in stopping children from becoming short-sighted, Australian researchers have found.
The findings, presented to the Australasian Ophthalmic and Visual Sciences Meeting in Canberra this week, appear to overturn the long-held view that education and close work are the key drivers of myopia.
Instead they suggest the ability to develop myopia is strongly influenced by environmental factors.
They will also be a boon to public health officials in the region as myopia is reaching epidemic proportions across urban Asia.
Dr Ian Morgan, of the Australian Research Council Centre of Excellence in Vision Science, says there has been a dramatic escalation in myopia rates in East Asia during the past 30 years.
Morgan says 90% of conscription-aged males in Singapore are now myopic.
This compares with figures from the 1960s to the 70s when only 20-30% of 17-year-old males had myopia.
During the same period, rates of myopia in Australia have increased from about 15% to 20-25%.
Morgan says it has been suggested there may be an East Asian genetic susceptibility to environmental risk factors associated with intensive education and urbanisation.
But he says this can be discounted because those of South Asian, or Indian, ethnicity growing up in Singapore are as myopic as the Chinese and Malay populations.
"This phenomenon cannot plausibly be explained in terms of changes in gene pools," the Australian National University researcher says.
"A gene pool doesn't change that fast."
Instead Morgan and colleague Dr Kathy Rose, of the Faculty of Health Sciences at the University of Sydney, have found the time children spend outdoors is the critical factor.
A comparison of children of Chinese origin living in Singapore and Sydney, which matched the subjects for age and parental myopia, shows the rate of myopia in Singaporean children is 10 times higher.
But Morgan says the Sydney-based children spend significantly more time in near-work activity, reading twice as many books per week.
The key difference in their weekly activities was in time spent outdoors with Sydney-based children outside almost four times longer than their Singapore counterparts.
"What children are doing in Australia at the moment seems to be right," he says.
Morgan believes the exposure to sunlight cuts myopia rates by encouraging the release of dopamine.
Dopamine is known to inhibit eye growth and myopia is a condition caused by excessive eye growth.
Morgan says while they will begin experiments to assess this theory, the findings are concrete enough to inform public health policy.
"The findings provide a means of prevention and are enough to start authorities thinking about time outdoors as a public health strategy."
Morgan says a prevention strategy is needed because severe myopia increases the risk of retinal detachment, which can lead to blindness.
He says Singapore faces the serious public health threat of having as much as 10% of its population developing a serious retinal problem later in life.
Benefits of Sunlight
However surprising it may be, some doctors are now describing sunlight as beneficial rather than a cancer risk to be avoided at all costs. Though the dangers of sun exposure–like skin cancer and blindness–should still be taken into consideration, sunlight is still a part of a healthy lifestyle.
Sunlight can reduce the effects of SAD, or seasonal affective disorder—more commonly known as seasonal depression. Doctors have suggested taking walks daily for people who suffer from this disorder, even when the sky is overcast. This has shown to help improve seasonal depression even more than the use of sunlamps.
It appears, through years’ long studies of people who live in sunnier climates and people who are exposed to sunlight through their work situations, that sunlight can actually decrease risk of colon and breast cancer.
In another study, patients who were put in hospital rooms that were sunny requested less pain medication than patients in windowless rooms. Whether the pain is lessened by the sunlight or the patients’ awareness of their pain levels decreased during the study is unclear.
People who are suffering from jet lag can use the sunlight in the area of their destination to reset their internal clock. Exposure to daylight can hasten the body’s ability to get on a sleep schedule that matches the time zone they are in.
Sunlight provides the body with the means to produce Vitamin D. Vitamin D helps the body in various biological functions: It promotes calcium absorption, which in turn deters bone loss; it may help maintain a healthy immune system; it could possibly be a part of the process of cell differentiation.
Of course, it is always smart to practice moderation in everything. However, the connection between good health and sunlight can not be ignored.
Posted by SANJIDA AFROJ at 10:20 PM