MedWire News: Nicotine levels in toenail clippings can indicate a woman's risk of developing heart disease, US research shows.

"Using toenail nicotine is a novel way to objectively measure exposure to tobacco smoke, and ultimately, to increase our understanding of tobacco-related illnesses," explained lead researcher Dr Wael Al-Delaimy, from the University of California in San Diego.

He added: "It has advantages over using other biomarkers and could become a useful test to identify high-risk individuals in the future. This would be especially helpful in situations where smoking history is not available or is biased."

Dr Al-Delaimy and team analysed nicotine levels in toenail clippings collected from 62,641 women, aged between 36 and 61 years, who participated in a long-term health study between 1984 and 1998.

Over the course of the study, 905 of the women developed coronary heart disease.

Analysis revealed that women with the highest levels of nicotine in their toenails were 3.44 times more likely to develop heart disease than those with the lowest levels of nicotine in their toenails.

Furthermore, the higher the level of nicotine in a woman's toenail clippings, the greater her risk was of developing heart disease.

The association remained significant after accounting for age, body mass index, high cholesterol and other risk factors, says the team.

Writing in the American Journal of Epidemiology, Dr Al-Delaimy and colleagues conclude: "Toenail nicotine levels are predictive of coronary heart disease among women independent of other risk factors and remained significant even after adjustment for history of cigarette smoking."