The majority of hip fractures are caused by a simple fall inside the home. Frail, elderly people are particularly susceptible to falls, given their many coexisting medical conditions that influence gait, balance, and coordination. Fracture incidence is directly related to age, doubling with each decade beyond age fifty. Women are much more commonly affected than men, by a ratio of 2.5 or 3 to 1. The white population in the United States is much more commonly affected than the African-American, Hispanic, or Asian populations. Other factors associated with injury include osteoporosis and osteomalacia, a history of smoking, excessive use of alcohol and caffeine, physical inactivity, and previous hip fracture.