By Jen Christensen, CNN    (CNN) — After years of recommending regular aspirin to prevent heart attack and stroke, scientists now see little benefit for most healthy people, and say it may contribute to a risk of bleeding in your stomach or brain that goes up as you get older.The US Preventive Service Task Force has finalized its latest recommendations on low-dose aspirin regimens and now says people over 60 should not start taking a daily aspirin for primary prevention of heart problems, in most cases.