The great positive impact of public health programs is widely acknowledged. Due in part to the policies and actions developed through public health, the 20th century registered a decrease in the mortality rates for infants and children and a continual increase in life expectancy in most parts of the world. For example, it is estimated that life expectancy has increased for Americans by thirty years since 1900,[54] and worldwide by six years since 1990.[55]
Although 50% of cardiovascular-disease risk is genetic, the other 50% can be modified by how you live your life, according to Dr. Eugenia Gianos, director of Women’s Heart Health at Lenox Hill Hospital in New York City. “This means you can greatly reduce a high genetic risk or greatly worsen a low genetic risk,” she says. “Your fate really lies largely in your hands.”
Personal health also depends partially on the social structure of a person's life. The maintenance of strong social relationships, volunteering, and other social activities have been linked to positive mental health and also increased longevity. One American study among seniors over age 70, found that frequent volunteering was associated with reduced risk of dying compared with older persons who did not volunteer, regardless of physical health status.[57] Another study from Singapore reported that volunteering retirees had significantly better cognitive performance scores, fewer depressive symptoms, and better mental well-being and life satisfaction than non-volunteering retirees.[58]

Health, as defined by the World Health Organization (WHO), is "a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity."[1][2] This definition has been subject to controversy, as it may have limited value for implementation.[3][4][5] Health may be defined as the ability to adapt and manage physical, mental and social challenges throughout life.[6]