For all the good aspirin can do in preventing second heart attacks and strokes, taking it daily can boost some risks, too — of ulcers, for example, and of bleeding in the brain or gut. iStockphoto hide caption

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Volunteers search for needles and other drug paraphernalia along Church Street in Austin, Ind., in April. The region has recorded 142 new HIV cases since December, according to the state, in an outbreak tied to injected-opioid use. Seth Herald/Nurphoto/Corbis hide caption

itoggle caption Seth Herald/Nurphoto/Corbis

Science-based guidelines say there's no benefit to getting an EKG of heart activity before routine cataract surgery — even if the patient is old. But most doctors order such tests anyway. Bull's Eye/ImageZoo/Corbis hide caption

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Colored brain scan of a 17-year-old boy with mad cow disease. The bright yellow spots are a sign that the thalamus is damaged by diseased proteins. Simon Fraser/Science Source hide caption

itoggle caption Simon Fraser/Science Source