WATCH: Living in the city may not be heart healthy: Study

  • Now Playing: Boxers or briefs? Largest-ever study shows boxers may beat briefs for baby-making


  • Now Playing: Low-calorie diets affect men’s and women’s bodies differently, study shows


  • Now Playing: Opioids after wisdom teeth removal might set young people up for addiction


  • Now Playing: 92-year-old doctor shares her secrets to a long and happy life


  • Now Playing: Does a doctor’s gender affect women’s survival rates after a heart attack?


  • Now Playing: Secondhand smoke more dangerous for teens: Study


  • Now Playing: Living in the city may not be heart healthy: Study


  • Now Playing: Is it safe to breastfeed while drinking alcohol?


  • Now Playing: Don’t let vacation sabotage your workout: Try these tips


  • Now Playing: What is Parkinson’s disease?


  • Now Playing: American Society of Plastic Surgeons issues new warning over butt lift surgery


  • Now Playing: Health alert issued for salads containing beef, pork and poultry


  • Now Playing: Lung cancer deaths among women expected to increase worldwide: Study


  • Now Playing: Could soccer ‘heading’ lead to greater brain injury for women than men?


  • Now Playing: Alan Alda reveals he has Parkinson’s disease


  • Now Playing: Why you shouldn’t ignore sudden pain at night


  • Now Playing: What parents should really do about kids who are picky eaters


  • Now Playing: Researchers working on possible depression blood test


  • Now Playing: What to know about the popular ‘carnivory’ diet


  • Now Playing: What parents should know about youth football and heat strokes