The cells of obese women or those who smoke are “older” than those of other women, suggesting that these factors accelerate aging, according to a new study.

The age of a cell is indicated by the caps, or “telomeres,” on the ends of chromosomes. With every successive division of the cell, the telomeres get shorter and shorter.

“The difference in telomere length between being lean and being obese corresponds to 8.8 years of aging; smoking (previous or current) corresponds on average to 4.6 years of aging; and smoking a pack per day for 40 years corresponds to 7.4 years of aging,” Dr. Tim Spector, from St. Thomas’ Hospital in London, and colleagues report in The Lancet medical journal.

Obesity and smoking are associated with oxidative stress, which, in turn, has been shown to promote telomere erosion. Therefore, the researchers hypothesized that Obesity and Smoking may be linked to shortened telomeres.

To investigate, Spector’s team analyzed telomere length in 1122 white women between the ages of 18 and 76 years.

Telomere length fell steadily with age, as expected, the researchers found.

Further analysis revealed that the telomeres of obese women were significantly shorter than those of lean women. Smoking status was also tied to shortened telomeres and each pack-year of smoking further increased the amount of length lost.

“Our results emphasize the potential wide-ranging effects of the two most important preventable exposures in developed countries - cigarettes and obesity,” the team concludes.

SOURCE: Lancet, online June 14, 2005.