Last year, I mentioned some ongoing research suggesting a link between exposure to light and the development of breast cancer. As I mentioned then:

While we know a good deal about factors that can contribute to breast cancer risk–including genetics (such as mutations in the BRCA1 and BRCA2 genes) and lifestyle choices (late or no childbearing, high fat diet, lack of exercise), many environmental risks for breast cancer remain controversial. Even the effect of cigarette smoking on breast cancer development remains uncertain, as does the environmental light idea.

For a nice update and overview into the whole area, check out the story in today’s Chronicle by Richard Monastersky:

While trying to sleep in his apartment in the mid-1980s, Mr. Stevens noticed that the street lamp outside was so bright he could almost read in his bedroom. “You couldn’t do that a thousand years ago or even a few hundred years ago,” he says. “People just don’t experience dark anymore.”

That observation sent his brain racing. As an epidemiologist, Mr. Stevens had been puzzling over a curious trend in breast-cancer statistics: The rates shoot up as societies grow more industrialized. Many other cancers — stomach, colon, and liver cancers — become less prevalent as a country modernizes, largely because people benefit from better sanitation and safer food. But epidemiologists could not figure out why breast-cancer rates in modernized societies were five times the levels documented in the developing world.

Maybe it was electric lights, reasoned Mr. Stevens as he lay awake that night. “One of the big changes in the industrialized world is light at night.”

Monastersky discusses some of the research that has found evidence of such a relationship, but notes that unlike many of the trumped-up “controversies” discussed here at Aetiology, this one is genuine (making it, of course, much more interesting!) Check out the article for the whole scoop.