You can't shake that cough, maybe you're having a tougher time breathing, or you feel a little pressure in your chest. It could be a bunch of things: bronchitis, the start of pneumonia, a sign of emphysema ... or it could be asthma. Sure, asthma is more common in kids, but symptoms can start at any age. In fact, recent government reports show asthma rates are on the rise: One in 12 adults are now diagnosed with the disease. Though scientists don't know exactly why some adults develop asthma and others don't, they believe genetics and environmental factors may play …