If you need another reason to keep that New Year's resolution to quit smoking, here it is: a U.S. researcher says he has discovered smoking can disable a gene that protects against premature aging.

The gene, SIRT1 is one of a group that regulates chronic inflammation, cancer and aging. When it is highly active, or over-expressed in mice, worms and fruit flies, their lifespans are greatly increased.

Recent studies also show that SIRT1 helps ease the negative effects of stress, cell death and other processes involved in premature aging.

According to University of Rochester associate professor of Environmental Medicine, Irfan Rahman, the toxins in cigarette smoke can decrease production of SIRT1 in the lungs.

His research was published in two separate studies, in the American Journal of Respiratory Critical Care Medicine, appearing online Jan. 3, 2008, and in the American Journal of Physiology, appearing Dec. 27, 2007.

Rahman has spent years studying how the 4,700 toxic chemical compounds in cigarettes assault lung tissue.

In collaboration with researchers at Helsinki University Hospital in Finland, Rahman's team studied the levels of SIRT1 in the lungs of nonsmokers and smokers with and without chronic obstructive pulmonary disease (COPD). The disease's symptoms, common in smokers, include shortness of breath, increased mucus and coughing.

Thirty-seven patients from Helsinki who were undergoing an operation to remove part of their lungs for suspected cancer or a lung transplant provided tissue samples for the study. Researchers confirmed that SIRT1 was significantly lower in smokers who had COPD and in smokers who did not have disease, compared with nonsmokers.

Rahman said that by identifying the gene's role in pulmonary disease, scientists may one day be able to find ways to target SIRT1 and reverse lung damage.