Drinking a lot of coffee or tea has been linked to a lower risk of developing type 2 diabetes in a new analysis. Researchers led by Rachel Huxley of The University of Sydney pooled 18 studies conducted since 1966, which followed more than 500,000 people, of whom 21,000 developed diabetes. Taken together, the papers showed that people who had three to four cups of coffee a day had a 25 percent lower risk of diabetes compared with people who had one, two, or no cups of coffee. The risk of diabetes fell by 7 percent for each additional cup consumed. A similar association was found for decaffeinated coffee and tea.
The relationship held true even after accounting for any differences in such variables as body mass index, smoking, and, in some of the studies, socioeconomic status and total calories. Most of the studies also took into account whether coffee or tea drinkers were consuming less of other beverages. “So it’s not that these people were consuming less Coke or other sugary drinks,’’ Huxley said. The authors raised the possibility that some undetermined chemical in coffee and tea might have a beneficial effect on glucose metabolism and insulin sensitivity involved in diabetes.
BOTTOM LINE: People who drank coffee or tea had a lower risk of developing type 2 diabetes than people who didn’t.
CAUTIONS: Some of the studies pooled for the analysis were small, possibly leading to an overestimate of the association.
WHERE TO FIND IT: Archives of Internal Medicine, December 14/28
Nearsightedness on the rise
More Americans are becoming nearsighted, it appears from a new study that looked at levels of myopia dating back to the early 1970s. The National Health and Nutrition Examination Survey first measured myopia - blurry distance vision - in 1971 and 1972, but it tested vision only among people who wore glasses or contact lenses. A more recent NHANES survey, conducted from 1999 through 2004, tested all participants, potentially capturing more people who had myopia but also making comparisons difficult.To see whether myopia prevalence was truly growing, as other research around the world has suggested, epidemiologist Susan Vitale and her colleagues at the National Eye Institute compared data from the two US surveys using the same methods. They found that 41.6 percent of the recent survey participants had myopia compared with 25 percent of the participants from 30 years earlier. Among black participants, the prevalence more than doubled, rising from 13 percent to 33.5 percent, while among whites, myopia grew from 26.3 percent to 43 percent.
Other researchers have speculated that higher levels of education and the reading it involves may increase risk for myopia, and the authors note that racial inequities in education decreased over the 30 years between the two surveys.
BOTTOM LINE: Nearsightedness has become more common among Americans over the last three decades.
CAUTIONS: There may be slight differences in the devices used to measure visual acuity for the two surveys.
WHAT’S NEXT: Researchers are examining possible risk factors for myopia to help identify people who could benefit from corrected vision.
WHERE TO FIND IT: Archives of Ophthalmology, December
ELIZABETH COONEY
