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At a time when smoking rates are plummeting, teenage girls remain the most frequent and stubbornly persistent smokers.

They smoke, in large part, in a vain pursuit: Convinced that doing so will keep their weight down.

But the first detailed study of the common practice shows that, in fact, smoking and non-smoking teenage girls gain weight at exactly the same rate.

"Smoking is not associated with any difference in weight [or height] in girls," Igor Karp, a researcher in the department of epidemiology and biostatistics at McGill University in Montreal, said yesterday.

Boys who smoke, on the other hand, are leaner and shorter than their non-smoking peers, evidence that smoking actually stunts their growth.

"This is probably because girls reach puberty earlier, the growth spurt comes before they start smoking," Dr. Karp said.

The study, presented at the Canadian Cardiovascular Congress in Vancouver, involved almost 1,300 Montreal students beginning at age 12 or 13. They were followed for five years.

A whopping 73 per cent of girls and 42 per cent of boys smoked.

"There is an important public-health message here that we need to get to teenage girls: Smoking is not going to help you lose weight," said Louise Pilote, leader of Genesis, a study group investigating sex and gender difference in cardiovascular disease.

She said that is just one of many messages that need to be tailored to girls and women to improve their heart health.

"The bottom line is that women have poorer cardiovascular outcomes," Dr. Pilote said. "There is a big body of medical literature that tells us that, but very little that tells us why. We hope to change that."

Yesterday, Genesis researchers presented results of a number of studies that explored sex and gender differences in the diagnosis and treatment of heart patients.

Colleen Norris, a researcher in the faculty of nursing at the University of Alberta in Edmonton, poked holes in the belief that women and men who suffer heart attacks have markedly different symptoms. (A number of studies have shown that men tend to feel a bone-crushing chest pain, while women tend to have more subtle symptoms including indigestion, shoulder pain and shortness of breath.)

She said that, in fact, men and postmenopausal women have a broad range of symptoms that are quite similar. Pre- and perimenopausal women, on the other hand, have markedly different symptoms, yet they tend to be dismissed by physicians.

"Symptoms are clearly different based on menopausal status," Dr. Norris said.

Research by Karin Humphries, an epidemiologist in the division of cardiology at the University of British Columbia in Vancouver, showed that angiograms -- tests done to determine the health of coronary arteries -- are far less effective in women than men.

The study compared what happened to women and men with angina or other signs of blocked arteries after they were sent for testing. It showed that 24 per cent of women and 7 per cent of men were considered normal after an angiogram, meaning they didn't have artery disease.

Yet the so-called normal women were four times more likely than men to be hospitalized with serious heart problems in the 180 days following their discharge.

"Women with a 'normal' angio may have substantial disease," Dr. Humphries said. Her research suggests that women (or at least some women) should undergo different testing than men -- dobutamine echocardiography instead of traditional angio.

Dr. Pilote, for her part, presented findings of three studies that showed women and men with heart failure react differently to common cardiovascular drug treatments.

The research showed that angiotensin-converting enzyme (ACE) inhibitors are less effective in women than in men, but that beta blockers work about the same in both sexes.

A second study showed that women with heart failure do markedly better when treated with angiotensin receptor blockers (ARBs) than with ACE inhibitors.

The third study showed that statins, which are typically prescribed after someone has a heart attack, work about the same in women and men.

Dr. Pilote said these findings are all important because most studies of heart drugs involve only a very small percentage of women, and it is simply assumed that drugs work the same in both sexes.

Earlier research, which was not done by Genesis, showed that taking ASA dramatically reduced the risk of heart attacks in men but made little difference for women; on the other hand, ASA sharply reduced the risk of stroke in women, but had no effect on men.