Women Hospitalized Twice As Often As Males For Asthma, Stayed Longer

DGNews 23jan01

NORTHBROOK, IL -- January 23, 2001 -- In a study examining 10 years of high-risk asthma admissions to the Yale-New Haven Hospital, researchers found that high-risk women were admitted twice as often as men, stayed in the hospital almost a day longer, yet displayed lower levels of a blood marker of asthma severity.

Writing in the January issue of CHEST, the monthly peer-reviewed journal of the American College of Chest Physicians, David R. Trawick, M.D., Ph.D., along with two colleagues, studied data on 103 high-risk patients, ages 18 - 50, who had been admitted at least twice to the hospital for asthma attacks over a 10-year period. The 103 patients accounted for 382 admissions, of which 68.6 percent were for female patients.

The average hospital stay for men was about four days and for women almost five days. There was one male and one female death among the study group. Slightly over 14 percent of the 382 admissions required care in the medical intensive care unit (MICU), and slightly over seven percent were given mechanical ventilation. The proportion of men requiring intensive care and intubation was not significantly different from that of the female patients.

Of the 55 patients who, during at least one of their visits, was admitted to the MICU, 28 required intubation and mechanical ventilation. The duration of intubation was slightly over 67 hours for the women and almost 51 hours for the men.

The study pointed out that a national 1990 economic estimate of illness cost related to asthma hit US$6.2 billion. About $1.6 billion represented inpatient hospital services-the largest single direct medical expenditure in the total.

"For our study, we chose to examine data from high-risk patients since they have, by definition, an increased risk for repeat hospitalization for asthma," said Dr. Trawick, who is currently associated with the Pulmonary and Critical Care Unit of the University of Rochester Medical Center, Rochester, New York. "Furthermore, all our patients met the criteria for potentially fatal asthma which would subject them to a higher rate of illness and higher health care resource utilization."

The researchers found that, overall, male asthmatics exhibited higher carbon dioxide levels than did females. Carbon dioxide is a colorless, odorless gas given off from the lungs as a waste product of respiration. Carbon dioxide levels in the blood regulate the breathing rate. The acid-base balance of the blood and other body fluids is influenced by levels of carbon dioxide. Males admitted to the MICU had significantly higher carbon dioxide levels than their female counterparts. The highest levels were detected in males who were intubated for mechanical ventilation.

The researchers believe their study suggests that gender-specific differences in the ventilatory response to airflow obstruction or to high carbon dioxide levels in the blood could contribute to the gender-related differences in asthma hospitalizations. Hypercapnia, or excess carbon dioxide in the blood, during acute asthma is associated with severe airflow obstruction.

The researchers note that asthma patients who suffer from hypercapnia often have a longer duration of chronic asthma and are more likely to be steroid-dependent. They consider the partial pressure of carbon dioxide levels to be a gauge of severity of acute asthma exacerbation and to reflect some of the chronic features of the illness in the patients. But they could not explain why high-risk males in their study were more hypercapnic than the high-risk females in the study. They hypothesize that because males can exert greater maximal inspiratory and expiratory pressure levels, women may be more symptomatic at lower airway resistance levels. This factor could prompt clinicians to order arterial blood gas analysis earlier during their evaluation of an asthma attack, a procedure supported by the data in this study.