In osteoporosis, bones become less dense and more fragile and bone fractures occur more easily. Since the hormone estrogen keeps bone dense, osteoporosis is especially common in women after menopause as estrogen levels drop. Estimates suggest that half of all women will have an osteoporosis-related fracture after menopause. Health habits that prevent osteoporosis include adequate calcium and vitamin D intake, exercise, and avoiding tobacco and alcohol. Because broken bones (fractures) can be painful, costly, and disabling, it is important to prevent osteoporosis or to treat it at early stages before fractures occur. Statins (also called 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors) are drugs that doctors usually prescribe to treat high cholesterol. Laboratory studies show that statins have a favorable effect on bones. However, studies that have looked at whether people who take statins have fewer bone fractures than people who do not take statins have had mixed results, so it remains uncertain whether statins prevent osteoporosis.