This is the most common cause of abnormal heartbeat in older adults.

VOA: special.2009.08.12

The most common cause of COPD is long-term smoking or years of exposure to second-hand smoke.

VOA: standard.2010.06.21

But the most common cause is long-term smoking or years of breathing other people's smoke.

VOA: special.2010.06.23

Down syndrome is the most common genetic cause of mental retardation.

VOA: special.2009.09.09