One of my colleagues at Martha Stewart Living Omnimedia was having more and more difficulty breathing. She's a lifelong asthma sufferer, but she'd had the condition under control for years, which made these flare-ups all the more puzzling.

Had she changed her diet? No. Been exposed to any new plants or pets? No, again. Changed the cleaning products or detergents she was using? No. Bought some new items of furniture or a new carpet? No and no. Caught a cold? No. Recently changed her medication regimen? No, she didn't think so.

Here's what she knew had changed: Earlier in the year, the pulmonologist she had seen for years died. My colleague wasn't having problems with her asthma at the time, so she didn't seek out another doctor until she needed a new prescription for her inhaler. At their first meeting, she went over her detailed history with him and, at the end of the appointment, asked for the refill. Looking at the inhaler she held in her hand, he scribbled on his pad and handed her the slip. Over the next couple of weeks, her breathing became more shallow. She was wheezing and her chest felt tight. She was using her inhaler more often.