Asthma: An Adult Disease Too Adult-onset asthma is more common than you may think. Some experts say that up to 40 percent of new asthma sufferers show no symptoms until age forty, and many cases get overlooked by physicians due to symptomatic similarities with other age-related maladies. The prevalence of asthma has more than doubled since 1980, with over half a million Americans now being hospitalized by the ailment each year. The coughing and wheezing of an asthma attack are often induced by allergens and environmental triggers, including pollen, mold, pet dander, dust mites, cockroaches, tobacco smoke, cleaning products, and pollutants. Exposure to these triggers over a long period of time may be one reason for the increase in asthma symptoms among adults.