Using government data, they found that asymptomatic, or symptomless, peripheral artery disease (PAD) rates among women aged 40 and older rose from 4.1% in 1999-2000 to 6.3% in 2003-2004.
"A large number of people are at risk and don't know it," says researcher Andrew D. Sumner, MD, medical director of the Heart Station and Cardiac Prevention at Lehigh Valley Hospital in Allentown, Pa.
Among men, asymptomatic PAD rates fell from 3.3% in the earlier time period to 2.8% in the latter period.
The study was presented at the American Heart Association's Scientific Sessions 2007.
PAD and Heart Disease
In people with PAD, fatty deposits accumulate in the inner linings of artery walls, curbing the supply of oxygen-rich blood to limb muscles, particularly in the legs. It's a well-recognized risk factor for future heart attacks and strokes.
Starved for oxygen for long periods of time, leg muscles can cramp and begin hurting after people walk even short distances. Pain typically goes away after a few minutes of rest. But in severe cases of PAD, this leg pain occurs even at rest.
In the study, the researchers detected PAD before symptoms occurred by measuring the ratio of the blood pressure in the ankles and arms -- also referred to as the ankle-brachial index, or ABI. Those with an ABI of less than 0.9 were determined to have PAD.
Obesity and PAD
The increase in PAD among women appeared to be largely driven by a parallel rise in obesity, the study shows.
In the earlier time period studied, 32% of women met the criteria for obesity compared with 47% in the latter period. People with a body mass index (BMI) -- a ratio of height to weight -- of 30 or over are considered to be obese.
PAD Rates Highest in Elderly
For the study, Sumner and colleagues analyzed data from three successive National Health and Nutrition Examination Surveys (NHANES) between 1999 and 2004.Â A total of 5,376 Americans aged 40 and older with no history of cardiovascular disease were surveyed.
Driven by the increase in women, overall asymptomatic PAD rates rose from 3.7% in 1999-2000 to 4.6% in 2003-2004, the study showed.
Asymptomatic PAD rates were highest among those aged 70 and older, the study shows.
Sumner says he doesn't know why rates among men fell.
"But it could be that their [rates] of symptomatic PAD were increasing, so the overall [rate] of asymptomatic and symptomatic together is still rising in men," he says.
Opportunity for Early Intervention
Jonathan Halperin, MD, a cardiologist at Mount Sinai Medical Center in New York and a spokesman for the American Heart Association, tells WebMD that PAD is the forgotten cousin of cardiovascular disease (CVD). Early identification of patients, before symptoms occur, allows an opportunity for early intervention, he says.