A new report by government researchers finds the number of Americans with high blood pressure has climbed to almost one in three over the past decade, as Americans have gotten older and fatter. A little more than a decade ago, the number was closer to one in four. And two decades ago, it was falling. The report doesn't specifically examine reasons for the spike. But experts say the aging US population and the growing proportion of overweight and obese Americans are probably major contributors. The analysis of Census Bureau and health statistics appears in Hypertension, the journal of the American Heart Association. One expert on high blood pressure says the "big message" is that Americans need to pay more attention to their lifestyles -- and those who are overweight need to get slimmer.