As the nation’s collective waistline has swelled in recent decades, rates of asthma diagnoses also have accelerated. Indeed, much research has affirmed a link between the two conditions.

But doctors also recognize that asthma may not behave the same way among people who have different body types. With a variety of asthma medications on the market, what kinds work best for lean people and what kinds work best for obese people? The answer may be different for each group.

A new study suggests that people who are overweight or obese may have better results with the prescription pill sold as Singulair than with a type of inhaled steroid, while leaner people may have better luck with an inhaled steroid, called beclomethasone and sold as beclovent, vanceril and other brand names. The findings appear in the new issue of the European Respiratory Journal.

“It is increasingly recognized that obese people are more prone to develop asthma, but there is no information about whether obesity influences people’s responses to particular asthma medications,” says lead author Marc Peters-Golden, M.D., professor of internal medicine and director of the Fellowship Program in Pulmonary and Critical Care Medicine at the University of Michigan Medical School.

“Our findings are the first to suggest the possibility that obesity might be a factor that influences how well asthmatics respond to particular medications,” Peters-Golden says.

Singulair is the brand name of montelukast sodium and is sold by Merck & Co., which funded this study.

Researchers looked at data from four previous multi-center, randomized clinical trials from 3,073 patients with moderate asthma. The data included the patients’ responses to Singulair/montelukast, a beclomethasone inhaled steroid and a placebo, and the participants’ body mass index numbers, which placed them in the categories of normal, overweight and obese.

In general, the severity of people’s asthma was found to be greater among those in the overweight and obese groups, which supports findings from other studies.

In addition, the inhaled steroid was found to be better than Singulair at increasing the number of asthma control days (ACD) among people in the normal weight category. An ACD is defined as a day with no more than two puffs of an inhaler, no night-time awakenings and no asthma attacks.

On the other hand, the inhaled steroid resulted in a reduced effect in the percentage of ACDs among obese people in the study - that is, the benefit of the inhaled steroid declined with increasing body mass index.

In contrast, the positive impact of Singulair did not decrease in obese and overweight people when compared to its impact on people of normal weight. The research also suggests that the higher a person’s body mass index, the greater his or her response to Singulair compared to a placebo, a pill with no medicinal benefit. This is an indication, Peters-Golden says, that obese and overweight people may in fact respond better to this medication.

Still, he is not inclined to suggest that doctors change the way in which they prescribe medication - not yet, anyway.

“Our study looks back at material from previous trials. I’d like to see a prospective study in which lean patients and heavy patients are enrolled at the outset, and you compare both types of medications in both groups,” Peters-Golden says. If verified by other studies, this insight may help physicians to better tailor medication regimens to meet individual patient needs.

Peters-Golden also notes that much research about asthma and other conditions is exploring the possibility that genetic factors might explain individual variations in responses to medications. He says it is likely that a variety of factors, including genetic ones and acquired factors such as weight, combine in a complex and intertwined manner to influence a person’s reaction to medications.

Information about Singulair/montelukast: This medication, usually taken once a day, is a type of leukotriene antagonist - that is, it blocks leukotrienes in the body. Leukotrienes are chemicals in the human body that can affect the breathing passages. Information about the beclomethasone inhaled steroid: Beclomethasone is a steroid that prevents the release of substances in the body that cause inflammation. Inhalation of beclomethasone prevents asthma attacks and other conditions involving inflammations of the lung tissues.

In addition to Peters-Golden, other authors of the study were A. Swern, S.S. Bird, C.M. Hustad, E. Grant and J.M. Edelman, all of Merck & Co.

One of Peters-Golden’s primary research interests involves leukotrienes, and he has consulted for and spoken on behalf of a number of pharmaceutical companies, including Merck & Co.