Women's health is an example of population health, where health is defined by the World Health Organization as "a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity". Often treated as simply women's reproductive health, many groups argue for a broader definition pertaining to the overall health of women, better expressed as "The health of women". These differences are further exacerbated in developing countries where women, whose health includes both their risks and experiences, are further disadvantaged. Although women in industrialised countries have narrowed the gender gap in life expectancy and now live longer than men, in many areas of health they experience earlier and more severe disease with poorer outcomes. Gender remains an important social determinant of health, since women's health is influenced not just by their biology but also by conditions such as poverty, employment, and family responsibilities. Women have long been disadvantaged in many respects such as social and economic power which restricts their access to the necessities of life including health care, and the greater the level of disadvantage, such as in developing countries, the greater adverse impact on health. Women's reproductive and sexual health has a distinct difference compared to men's health. Even in developed countries pregnancy and childbirth are associated with substantial risks to women with maternal mortality accounting for more than a quarter of a million deaths per year, with large gaps between the developing and developed countries. Comorbidity from other non reproductive disease such as cardiovascular disease contribute to both the mortality and morbidity of pregnancy, including preeclampsia. Sexually transmitted infections have serious consequences for women and infants, with mother-to-child transmission leading to outcomes such as stillbirths and neonatal deaths, and pelvic inflammatory disease leading to infertility. In addition infertility from many other causes, birth control, unplanned pregnancy, unconsensual sexual activity and the struggle for access to abortion create other burdens for women. While the rates of the leading causes of death, cardiovascular disease, cancer and lung disease, are similar in women and men, women have different experiences. Lung cancer has overtaken all other types of cancer as the leading cause of cancer death in women, followed by breast cancer, colorectal, ovarian, uterine and cervical cancers. While smoking is the major cause of lung cancer, amongst nonsmoking women the risk of developing cancer is three times greater than amongst nonsmoking men. Despite this, breast cancer remains the commonest cancer in women in developed countries, and is one of the more important chronic diseases of women, while cervical cancer remains one of the commonest cancers in developing countries, associated with human papilloma virus (HPV), an important sexually transmitted disease. HPV vaccine together with screening offers the promise of controlling these diseases. Other important health issues for women include cardiovascular disease, depression, dementia, osteoporosis and anemia. A major impediment to advancing women's health has been their underrepresentation in research studies, an inequity being addressed in the United States and other western nations by the establishment of centers of excellence in women's health research and large scale clinical trials such as the Women's Health Initiative.
