November 08, 2009
Too Much Time Indoors Causes Myopia?

In sometimes subtle ways we are creating a civilization that is incompatible with some of our genetic inheritance. Some researchers working in Australia and Singapore were able too show that children who spend less time outdoors get myopia at higher rates.

The team looked only at children of Chinese ethnicity, to rule out genetic differences between races as an explanation for higher myopia rates in certain countries.

The result? On average the children in Sydney spent nearly 14 hours per week outside, and only 3 per cent developed myopia. In contrast, the children in Singapore spent just 3 hours outside, and 30 per cent developed myopia. Once again, close work had a minimal influence; the Australian children actually spent more time reading and in front of their computers than the Singaporeans (Archives of Ophthalmolology, vol 126, p 527).

Possibly the light hitting the eyeballs regulates their growth and insufficient light during development causes the eyeballs to grow incorrectly. The article describes the results of other research on causes of myopia. Click through if you have an interest.

Singapore with its dense population and high rise living strikes me as the sort of place where humans experience an environment far from our ancestral environments. Kids can't easily play outside when they live in a high rise. Cities really aren't good for raising children. By contrast, I feel fortunate that where I grew up I walked out the door and I was on a big plot of land bordering a forest and farm land. I could get thoroughly dirty (an opportunity rarely missed). The dirt probably helped my immune system develop from all the microbes it came into contact with. Plus, summers were spent outside for very long hours. Lots of vitamin D and light hitting my eyeballs.

Share |      Randall Parker, 2009 November 08 09:11 PM  Human Unnatural Environment

PacRim Jim said at November 9, 2009 12:38 AM:

I, too, spent a lot of time outdoors. Reward: The 20/10 vision was a great help at finals time in the lecture hall.

William O. B'Livion. said at November 9, 2009 1:51 AM:

If you're in that big blue room with the lousy AC and the single big bright light your visual focus is going to bounce from infinity to close in a LOT more than if you're in a smaller room, even if you're not drooling in front of the idiot box, playing on the computer or reading a book.

odograph said at November 9, 2009 8:30 AM:

I've always had this suspicion. It just didn't seem right that we could have evolved to such a high population with myopia.

Rick Caird said at November 9, 2009 3:46 PM:

I suggest to odograph that survival of the fittest limited those with myopia until the relative safety of civilization allowed the myopic to live long enough to reproduce.

D.Meris said at November 9, 2009 4:20 PM:

OK - Great article. However, being outside isn't the only factor that should be configured in myopia (non-congenital). As a rural child (very, very rural - grew up learning to cook on a wood stove) I was outside all day long. Barefoot and having fun. Problem was, I loved to read. My parents encouraged reading - bought as many books through the scholastic magazine offered at school each month, drove us to the libraries in several different towns, book mobile, you name it - we read, read, read. Thing is, if you are outside all day helping with farming, playing and play outside in summer until dark falls at 10 pm, well that cuts into your reading time. So lights go on in the bedroom. As long as we were in bed on time, we could read and the light was allowed to stay on. Neither of our parents or grandparents on either side needed glasses. My sister and I (but not our older brother and sister - who liked to read - but not as much as we did and so went to bed with the lights off)both became nearsighted. New studies show that leaving a light on in the bedroom increases the chance for myopia. It seems the eyes need dark as well as light to grow properly. I didn't know that when I had children and our first child went to bed and read for a bit, but liked to sleep and so never kept the light on. Our second child read more, but her big issue was she was afraid of the dark - a night light didn't cut it - so , the light was left on. Both children were outside all the time. Being inside was punishment more than fun. However our oldest daughter has perfect eyesight and our youngest - who needed a bright light on at night has myopia.
I agree, outside is the best all around for children, but lights at night present a problem as well.

Andrew Myers said at November 9, 2009 4:24 PM:

Rick doesn't seem to have a good intuitive understanding of natural selection.
A negative trait like myopia would be ruthlessly eliminated by evolution under ancient conditions, and would be at a prevalence nowhere near 30%. It's well known that myopia is related to too much close vision in children, which wasn't a problem prior to the last couple of centuries. In other words, a lot of our caveman ancestors would have become myopic under current living conditions -- probably even more than today.

agesilaus said at November 9, 2009 5:31 PM:

Myopia has long been correlated with higher IQ and reading. More reading = more myopia and one might suspect that more time indoors might = more reading.

Randall Parker said at November 9, 2009 5:33 PM:

Rick Caird,

Industrial civilization is too young for much time to generate new mutations. So selective pressures are unlikely to be the cause of myopia.

I didn't refer to it in the post above but another suggested cause: more sugar causing more insulin and insulin-like growth factor (IGF) and then the insulin and/or IGF causes incorrect growth rate of the eyeballs. Seems plausible.

Toadal said at November 9, 2009 9:37 PM:

My identical twin brother and I were both outdoorsy, (rural Ohio) competitive, teen athletes in the late 1960s who were always nearly the same height, weight, and IQ. However, I became myopic at 22 while he never required glasses.

Perhaps it is because our educations differed, I received a bachelor of science degree while he attained a two-year technical college degree.

Tristan said at November 9, 2009 11:43 PM:

Don't skyscrapers have windows?

Beth Donovan said at November 10, 2009 5:34 AM:

Obviously, the solution is for more kids to have weeping willow trees under which to read!

That was my favorite reading spot in summers when I was growing up.

The Conscious Life said at November 16, 2009 4:58 PM:

I live in Singapore, but luckily, I got to live in a literally down-to-earth home during my childhood. Now I'm living in the mid air simply because the price of a bungalow is prohibitive. I don't see how most kids in Singapore can ever avoid myopia at some point in their lives, if this research is anything to go by. But thank goodness there's Lasik surgery which is in demand here.

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