Preventive healthcare, or prophylaxis is the application of healthcare measures to prevent diseases.^[1] Disease and disability are affected by environmental factors, genetic predisposition, disease agents, and lifestyle choices, and are dynamic processes which begin before individuals realize they are affected. Disease prevention relies on anticipatory actions that can be categorized as primal,^[2][3] primary, secondary, and tertiary prevention.^[1]

Each year, millions of people die of preventable deaths. A 2004 study showed that about half of all deaths in the United States in 2000 were due to preventable behaviors and exposures.^[4] Leading causes included cardiovascular disease, chronic respiratory disease, unintentional injuries, diabetes, and certain infectious diseases.^[4] This same study estimates that 400,000 people die each year in the United States due to poor diet and a sedentary lifestyle.^[4] According to estimates made by the World Health Organization (WHO), about 55 million people died worldwide in 2011, two thirds of this group from non-communicable diseases, including cancer, diabetes, and chronic cardiovascular and lung diseases.^[5] This is an increase from the year 2000, during which 60% of deaths were attributed to these diseases.^[5]