WASHINGTON -- The use of a once-a-day inhaler for chronic bronchitis or emphysema for longer than one month increases the risk of heart attack, stroke or cardiovascular death by 58 percent, a new study says.

An analysis of 17 clinical trials involving 4,783 patients with chronic obstructive pulmonary disease (COPD) revealed the adverse cardiovascular outcomes for those using inhaled anticholinergics as opposed to a placebo or some other kind of treatment.

"A regulatory reassessment of the cardiovascular safety concerns with this class of inhalers is urgently needed," said study co-author Sonal Singh of Wake Forest University School of Medicine in North Carolina.

The risk of death was most salient in five clinical trials of more than six months duration, according to the study published in the September 24 edition of the Journal of the American Medical Association (JAMA).

Anticholinergics belong to a class of drugs that dilate respiratory pathways to ease breathing and reduce bronchospasm, a sudden tightening of the bronchial tubes.

The two most commonly prescribed anticholinergics are tiotropium bromide, marketed as Spiriva by US pharmaceutical Pfizer, and ipratropium bromide or Atrovent, produced and marketed by the German firm Boehringer Ingelheim.

"Patients with COPD who use these inhalers are at a high risk of excess serious cardiovascular events due to their use," said Singh, a co-author of the study with Yoon Lake of Britain's University of East Anglia.

"In absolute terms, if these inhalers are used for one year, nearly one in 40 patients using these inhalers may develop cardiac death related to the drug, and nearly one in 174 patients may develop a heart attack associated with these inhalers."

COPD is the fourth leading cause of chronic illness and death in the United States, and is projected to rank fifth among worldwide health problems in 2020, a Wake Forest University statement said.

Heart attack is the leading cause of death in people with COPD.

Pfizer's Spiriva, taken in one daily dose, is the most commonly prescribed and widely-used long-acting treatment for COPD symptoms. More than eight million patients have used it since it was approved in 2002.

Pfizer and Boehringer Ingelheim fiercely contested the findings, arguing the research was flawed and furnishing data of their own showing Spiriva was safe.

In a statement the companies said Boehringer Ingelheim had conducted 30 rigorously controlled clinical trials demonstrating "there is no increased risk of death (all-cause) or death due to cardiovascular events in patients treated with Spiriva.

"Both companies considered it important to release these data to ensure doctors have the most comprehensive, up-to-date safety information on tiotropium in order to make the best treatment decisions for their patients," the statement said.