include ending child marriage in the successor sustainable development goals adopted in september 2015, where ending this practice by 2030 is a target of sdg 5 gender equality (see above). while some progress is being made in reducing child marriage, particularly for girls under fifteen, the prospects are daunting. the indicator for this will be the percentage of women aged 20–24 who were married or in a union before the age of eighteen. efforts to end child marriage include legislation and ensuring enforcement together with empowering women and girls. to raise awareness, the inaugural un international day of the girl child in 2012 was dedicated to ending child marriage. menstrual cycle main articles: menstrual cycle and menopause women's menstrual cycles, the approximately monthly cycle of changes in the reproductive system, can pose significant challenges for women in their reproductive years (the early teens to about 50 years of age). these include the physiological changes that can effect physical and mental health, symptoms of ovulation and the regular shedding of the inner lining of the uterus (endometrium) accompanied by vaginal bleeding (menses or menstruation). the onset of menstruation (menarche) may be alarming to unprepared girls and mistaken for illness. menstruation can place undue burdens on women in terms of their ability to participate in activities, and access to menstrual aids such as tampons and sanitary pads. this is particularly acute amongst poorer socioeconomic groups where they may represent a financial burden and in developing countries where menstruation can be an impediment to a girl's education. equally challenging for women are the physiological and emotional changes associated with the cessation of menses (menopause or climacteric). while typically occurring gradually towards the end of the fifth decade in life marked by irregular bleeding the cessation of ovulation and menstruation is accompanied by marked changes in hormonal activity, both by the ovary itself (oestrogen and progesterone) and the pituitary gland (follicle stimulating hormone or fsh and luteinizing hormone or lh). these hormonal changes may be associated with both systemic sensations such as hot flashes and local changes to the reproductive tract such as reduced vaginal secretions and lubrication. while menopause may bring relief from symptoms of menstruation and fear of pregnancy it may also be accompanied by emotional and psychological changes associated with the symbolism of the loss of fertility and a reminder of aging and possible loss of desirability. while menopause generally occurs naturally as a physiological process it may occur earlier (premature menopause) as a result of disease or from medical or surgical intervention. when menopause occurs prematurely the adverse consequences may be more severe. other issues other reproductive and sexual health issues include sex education, puberty, sexuality and sexual function. women also experience a number of issues related to the health of their breasts and genital tract, which fall into the scope of gynaecology. non-reproductive health women and men have different experiences of the same illnesses, especially cardiovascular disease, cancer, depression and dementia, and are more prone to urinary tract infections than men. cardiovascular disease cardiovascular disease is the leading cause of death (30%) amongst women in the united states, and the leading cause of chronic disease amongst them, affecting nearly 40% (gronowski and schindler, tables i and iv). the onset occurs at a later age in women than in men. for instance the incidence of stroke in women under the age of 80 is less than that in men, but higher in those aged over 80. overall the lifetime risk of stroke in women exceeds that in men. the risk of cardiovascular disease amongst those with diabetes and amongst smokers is also higher in women than in men. many aspects of cardiovascular disease vary between women and men, including risk factors, prevalence, physiology, symptoms, response to intervention and outcome. cancer women and men have approximately equal risk of dying from cancer, which accounts for about a quarter of all deaths, and is the second leading cause of death. however the relative incidence of different cancers varies between women and men. in the united states the three commonest types of cancer of women in 2012 were lung, breast and colorectal cancers. in addition other important cancers in women, in order of importance, are ovarian, uterine (including endometrial and cervical cancers (gronowski and schindler, table iii). similar figures were reported in 2016. while cancer death rates rose rapidly during the twentieth century, the increase was less and later in women due to differences in smoking rates. more recently cancer death rates have started to decline as the use of tobacco becomes less common. between 1991 and 2012, the death rate in women declined by 19% (less than in men). in the early twentieth century death from uterine (uterine body and cervix) cancers was the leading cause of cancer death in women, who had a higher cancer mortality than men. from the 1930s onwards, uterine cancer deaths declined, primarily due to lower death rates from cervical cancer following the availability of the papanicolaou (pap) screening test. this resulted in an overall reduction of cancer deaths in women between the 1940s and 1970s, when rising rates of lung cancer led to an overall increase. by the 1950s the decline in uterine cancer left breast cancer as the leading cause of cancer death until it was overtaken by lung cancer in the 1980s. all three cancers (lung, breast, uterus) are now declining in cancer death rates (siegel et al. figure 8), but more women die from lung cancer every year than from breast, ovarian, and uterine cancers combined. overall about 20% of people found to have lung cancer are never smokers, yet amongst nonsmoking women the risk of developing lung cancer is three times greater than amongst men who never smoked. in addition to mortality, cancer is a cause of considerable morbidity in women. women have a lower lifetime probability of being diagnosed with cancer (38% vs 45% for men), but are more likely to be diagnosed with cancer at an earlier age. breast cancer main article: breast cancer breast cancer is the second most common cancer in the world and the most common among women. it is also among the ten most common chronic diseases of women, and a substantial contributor to loss of quality of life (gronowski and schindler, table iv). globally, it accounts for 25% of all cancers. in 2016, breast cancer is the most common cancer diagnosed among women in both developed and developing countries, accounting for nearly 30% of all cases, and worldwide accounts for one and a half million cases and over half a million deaths, being the fifth most common cause of cancer death overall and the second in developed regions. geographic variation in incidence is the opposite of that of cervical cancer, being highest in northern america and lowest in eastern and middle africa, but mortality rates are relatively constant, resulting in a wide variance in case mortality, ranging from 25% in developed regions to 37% in developing regions, and with 62% of deaths occurring in developing countries. cervical cancer main article: cervical cancer globally, cervical cancer is the fourth commonest cancer amongst women, particularly those of lower socioeconomic status. women in this group have reduced access to health care, high rates of child and forced marriage, parity, polygamy and exposure to stis from multiple sexual contacts of male partners. all of these factors place them at higher risk. in developing countries, cervical cancer accounts for 12% of cancer cases amongst women and is the second leading cause of death, where about 85% of the global burden of over 500,000 cases and 250,000 deaths from this disease occurred in 2012. the highest incidence occurs in eastern africa, where with middle africa, cervical cancer is the commonest cancer in women. the case fatality rate of 52% is also higher in developing countries than in developed countries (43%), and the mortality rate varies by 18-fold between regions of the world. cervical cancer is associated with human papillomavirus (hpv), which has also been implicated in cancers of the vulva, vagina, anus, and oropharynx. almost 300 million women worldwide have been infected with hpv, one of the commoner sexually transmitted infections, and 5% of the 13 million new cases of cancer in the world have been attributed to hpv. in developed countries, screening for cervical cancer using the pap test has identified pre-cancerous changes in the cervix, at least in those women with access to health care. also an hpv vaccine programme is available in 45 countries. screening and prevention programmes have limited availability in developing countries although inexpensive low technology programmes are being developed, but access to treatment is also limited. if applied globally, hpv vaccination at 70% coverage could save the lives of 4 million women from cervical cancer, since most cases occur in developing countries. ovarian cancer main article: ovarian cancer by contrast, ovarian cancer, the leading cause of reproductive organ cancer deaths, and the fifth commonest cause of cancer deaths in women in the united states, lacks an effective screening programme, and is predominantly a disease of women in industrialised countries. because it is largely asymptomatic in its earliest stages, more than 50% of women have stage iii or higher cancer (spread beyond the ovaries) by the time they are diagnosed, with a consequent poor prognosis. mental health almost 25% of women will experience mental health issues over their lifetime. women are at higher risk than men from anxiety, depression, and psychosomatic complaints. globally, depression is the leading disease burden. in the united states, women have depression twice as often as men. the economic costs of depression in american women are estimated to be $20 billion every year. the risks of depression in women have been linked to changing hormonal environment that women experience, including puberty, menstruation, pregnancy, childbirth and the menopause. women also metabolise drugs used to treat depression differently to men. suicide rates are less in women than men (<1% vs. 2.4%), but are a leading cause of death for women under the age of 60. in the united kingdom, the women's mental health taskforce was formed aiming to address differences in mental health experiences and needs between women and men. dementia the prevalence of alzheimer's disease in the united states is estimated at 5.1 million, and of these two thirds are women. furthermore, women are far more likely to be the primary caregivers of adult family members with depression, so that they bear both the risks and burdens of this disease. the lifetime risk for a woman of developing alzheimer's disease is twice that of men. part of this difference may be due to life expectancy, but changing hormonal status over their lifetime may also play a par as may differences in gene expression. deaths due to dementia are higher in women than men (4.5% of deaths vs. 2.0%). bone health osteoporosis ranks sixth amongst chronic diseases of women in the united states, with an overall prevalence of 18%, and a much higher rate involving the femur, neck or lumbar spine amongst women (16%) than men (4%), over the age of 50 (gronowski and schindler, table iv). osteoporosis is a risk factor for bone fracture and about 20% of senior citizens who sustain a hip fracture die within a year. the gender gap is largely the result of the reduction of estrogen levels in women following the menopause. hormone replacement therapy (hrt) has been shown to reduce this risk by 25–30%, and was a common reason for prescribing it during the 1980s and 1990s. however the women's health initiative (whi) study that demonstrated that the risks of hrt outweighed the benefits has since led to a decline in hrt usage. anaemia anaemia is a major global health problem for women. women are affected more than men, in which up to 30% of women being found to be anaemic and 42% of pregnant women. anaemia is linked to a number of adverse health outcomes including a poor pregnancy outcome and impaired cognitive function (decreased concentration and attention). the main cause of anaemia is iron deficiency. in united states women iron deficiency anaemia (ida) affects 37% of pregnant women, but globally the prevalence is as high as 80%. ida starts in adolescence, from excess menstrual blood loss, compounded by the increased demand for iron