For the first time, it seems that more than half of all insured Americans are taking prescription medicines regularly for chronic health problems.

That's according to a new study by Medco Health Solutions. The most widely used drugs are those to lower high blood pressure and cholesterol.

Experts say the data reflect not just worsening public health but better medicines for chronic conditions and more aggressive treatment by doctors. It also shows the effect of the pharmaceutical industry's relentless advertising.

Doctors predict that unless something changes with the way health is managed in the country, the proportion of Americans on chronic medications can only grow.

The company examined prescription records from 2001 to 2007 of a representative sample of 2.5 million customers, from newborns to the elderly.