Regular aspirin use can prevent cardiovascular disease (CVD) events (heart attack or stroke) in people with no previous CVD and decrease the chances of developing colorectal cancer (CRC). However, aspirin can cause serious bleeding in the digestive tract or brain. Balancing these different benefits and harms can be challenging. In 2009, the USPSTF recommended that men aged 45 to 79 years take aspirin if the chances of preventing heart attack outweighed the chances of bleeding and that women aged 55 to 79 years take aspirin if the chances of reducing stroke outweighed the chances of bleeding. At that time, the USPSTF also recommended that men younger than 45 years and women younger than 55 years who have not previously had a heart attack or stroke not take aspirin for prevention and that the balance of benefits and harms at age 80 years or older were unclear. In 2007, the USPSTF recommended against use of aspirin to prevent CRC in adults at average risk for CRC. The USPSTF wanted to update recommendations for using aspirin to prevent CVD and CRC based on new information.