Editing Life expectancy (section)

===Sex differences===
[[File:Healthy life expectancy bar chart -world -sex.png|thumb|300px|Life expectancy and healthy life expectancy by sex in 2019<ref name="who_2019" />]]
[[File:LifeExpectancyBetweenFemaleAndMales.jpg|thumb|Pink: Countries where female life expectancy at birth is higher than males. Blue: A few countries in southern Africa where females have shorter lives due to [[AIDS]]. (2015)<ref>{{cite web|url=http://smart-unit-converter.com/life-expectancy.php|title=How long will I live? Estimate remaining life expectancy for all countries in the world|vauthors=Pele L}}</ref>]]
[[File:Comparison of male and female life expectancy -world.svg|thumb|right|300px|''"Gender Die Gap"'': global female life expectancy gap at birth for countries and territories as defined by [[World Health Organization|WHO]] for 2019. Open the original [https://upload.wikimedia.org/wikipedia/commons/b/b3/Comparison_of_male_and_female_life_expectancy_-world.svg svg-file] and hover over a bubble to show its data. The square of the bubbles is proportional to country population based on estimation of the [[UN]].]]
In the present, female human life expectancy is greater than that of males, despite females having higher morbidity rates (see [[health survival paradox]]). There are many potential reasons for this. Traditional arguments tend to favor sociology-environmental factors: historically, men have generally consumed more [[tobacco]], [[Alcoholic drink|alcohol]], and [[drug]]s than women in most societies, and are more likely to die from many associated diseases such as [[lung cancer]], [[tuberculosis]], and [[cirrhosis of the liver]].<ref name=worldhealth/> Men are also more likely to die from injuries, whether unintentional (such as [[Occupational safety and health|occupational]], [[war]], or [[car wrecks]]) or intentional ([[suicide]]).<ref name=worldhealth>{{cite web|publisher=World Health Organization|year=2004|work=The world health report 2004 – changing history|title=Annex Table 2: Deaths by cause, sex and mortality stratum in WHO regions, estimates for 2002|url=https://www.who.int/entity/whr/2004/annex/topic/en/annex_2_en.pdf|access-date=1 November 2008}}</ref> Men are also more likely to die from most of the leading causes of death (some already stated above) than women. Some of these in the United States include cancer of the respiratory system, motor vehicle accidents, suicide, cirrhosis of the liver, emphysema, prostate cancer, and coronary heart disease.<ref name="Santrock"/> These far outweigh the female mortality rate from breast cancer and cervical cancer. In the past, [[maternal death|mortality rates for females in child-bearing age groups]] were higher than for males at the same age.

A paper from 2015 found that female foetuses have a higher mortality rate than male foetuses.<ref name="pmid25825766">{{cite journal|vauthors=Orzack SH, Stubblefield JW, Akmaev VR, Colls P, Munné S, Scholl T, Steinsaltz D, Zuckerman JE|title=The human sex ratio from conception to birth|journal=Proceedings of the National Academy of Sciences of the United States of America|volume=112|issue=16|pages=E2102–11|date=April 2015|pmid=25825766|pmc=4413259|doi=10.1073/pnas.1416546112|doi-access=free|bibcode=2015PNAS..112E2102O}}</ref> This finding contradicts papers dating from 2002 and earlier that attribute the male sex to higher in-utero mortality rates.<ref name = "Kalben_2000">{{cite journal|vauthors=Kalben BB|title=Why men die younger: causes of mortality differences by sex.|journal=North American Actuarial Journal|date=October 2000|volume=4|issue=4|pages=83–111|doi=10.1080/10920277.2000.10595939|url=http://www.soa.org/library/monographs/life/why-men-die-younger-causes-of-mortality-differences-by-sex/2001/january/m-li01-1-05.pdf|access-date=31 October 2011|archive-date=13 September 2017|archive-url=https://web.archive.org/web/20170913135329/http://www.soa.org/library/monographs/life/why-men-die-younger-causes-of-mortality-differences-by-sex/2001/january/m-li01-1-05.pdf|url-status=dead}}</ref><ref>{{cite journal|vauthors=Naeye RL, Burt LS, Wright DL, Blanc WA, Tatter D|title=Neonatal mortality, the male disadvantage|journal=Pediatrics|volume=48|issue=6|pages=902–906|date=December 1971|pmid=5129451|doi=10.1542/peds.48.6.902}}</ref><ref>{{cite journal|vauthors=Waldron I|title=Sex differences in human mortality: the role of genetic factors|journal=Social Science & Medicine|volume=17|issue=6|pages=321–333|date=1983-01-01|pmid=6344225|doi=10.1016/0277-9536(83)90234-4|author-link1=Ingrid Waldron}}</ref> Among the smallest premature babies (those under {{Convert|2|lb|g|abbr=none}}), females have a higher survival rate. At the other extreme, about 90% of individuals aged 110 are female. The difference in life expectancy between men and women in the United States dropped from 7.8&nbsp;years in 1979 to 5.3&nbsp;years in 2005, with women expected to live to age&nbsp;80.1 in 2005.<ref>{{cite web|vauthors=Hitti M|title=U.S. Life Expectancy Best Ever, Says CDC|work=eMedicine|publisher=[[WebMD]]|date=28 February 2005|url=http://www.webmd.com/healthy-aging/news/20050228/us-life-expectancy-best-ever-says-cdc|access-date=18 January 2011}}</ref> Data from the United Kingdom shows the gap in life expectancy between men and women decreasing in later life. This may be attributable to the effects of infant mortality and young adult death rates.<ref>{{cite web|title=Life expectancy—care quality indicators|url=http://www.qualitywatch.org.uk/indicator/life-expectancy#vis-ref_221|website=QualityWatch|publisher=Nuffield Trust & Health Foundation|access-date=16 April 2015}}</ref>

Some argue that shorter male life expectancy is merely another manifestation of the general rule, seen in all mammal species, that larger-sized individuals within a species tend, on average, to have shorter lives.<ref>{{cite web|vauthors=Stindl R|url=http://jerrymondo.tripod.com/lgev/id1.html|title=Telemores, sexual size dimorphism and gender gap in life expectancy|publisher=Jerrymondo.tripod.com|access-date=4 November 2010}}</ref><ref>{{cite journal|vauthors=Samaras TT, Heigh GH|title=How human size affects longevity and mortality from degenerative diseases|journal=Townsend Letter for Doctors & Patients|volume=159|issue=78–85|pages=133–139}}</ref> This biological difference{{clarify|date=September 2022}} occurs because women have more resistance to infections and degenerative diseases.<ref name="Santrock"/>

In her extensive review of the existing literature, Kalben concluded that the fact that women live longer than men was observed at least as far back as 1750 and that, with relatively equal treatment, today males in all parts of the world experience greater mortality than females. However, Kalben's study was restricted to data in Western Europe alone, where the demographic transition occurred relatively early. United Nations statistics from mid-twentieth century onward, show that in all parts of the world, females have a higher life expectancy at age 60 than males.<ref>{{cite web|work=Department of Economic and Social Affairs|page=53|title=World Population Ageing 2015 (ST/ESA/SER.A/390)|url=https://www.un.org/en/development/desa/population/publications/pdf/ageing/WPA2015_Report.pdf|publisher=United Nations|access-date=11 March 2021}}</ref> Of 72 selected causes of death, only 6 yielded greater female than male age-adjusted death rates in 1998 in the United States. Except for birds, for almost all of the animal species studied, males have higher mortality than females. Evidence suggests that the sex mortality differential in people is due to both biological/genetic and environmental/behavioral risk and protective factors.<ref name = "Kalben_2000" />

One recent suggestion is that [[mitochondria]]l mutations which shorten lifespan continue to be expressed in males (but less so in females) because mitochondria are inherited only through the mother. By contrast, [[natural selection]] weeds out mitochondria that reduce female survival; therefore, such mitochondria are less likely to be passed on to the next generation. This thus suggests that females tend to live longer than males. The authors claim that this is a partial explanation.<ref>{{cite news|url=https://www.bbc.co.uk/news/health-19093442|title=Fruit flies offer DNA clue to why women live longer|publisher=BBC News|date=2 August 2012}}</ref><ref>{{cite web|vauthors=Myers PZ|author-link1=PZ Myers|date=6 February 2013|url=http://scienceblogs.com/pharyngula/2013/02/06/mothers-curse/|title=Mother's Curse}}</ref>

Another explanation is the [[unguarded X hypothesis]]. According to this hypothesis, one reason for why the average lifespan of males is not as long as that of females––by 18% on average, according to the study––is that they have a [[Y chromosome]] which cannot protect an individual from harmful genes expressed on the X chromosome, while a duplicate X chromosome, as present in female organisms, can ensure harmful genes are not [[gene expression|expressed]].<ref>{{cite news|vauthors=Gilbert L|date=4 March 2020|title=Why men (and other male animals) die younger: It's all in the Y chromosome|url=https://phys.org/news/2020-03-men-male-animals-die-younger.html|access-date=5 April 2020|work=phys.org}}</ref><ref>{{cite journal|vauthors=Xirocostas ZA, Everingham SE, Moles AT|title=The sex with the reduced sex chromosome dies earlier: a comparison across the tree of life|journal=Biology Letters|volume=16|issue=3|pages=20190867|date=March 2020|pmid=32126186|pmc=7115182|doi=10.1098/rsbl.2019.0867|doi-access=free}}</ref>

In developed countries, starting around 1880, death rates decreased faster among women, leading to differences in mortality rates between males and females. Before 1880, death rates were the same. In people born after 1900, the death rate of 50- to 70-year-old men was double that of women of the same age. Men may be more vulnerable to cardiovascular disease than women, but this susceptibility was evident only after deaths from other causes, such as infections, started to decline.<ref>{{cite web|vauthors=Rettner R|title=When Did Women Start to Outlive Men?|website=[[Live Science]]|date=6 July 2015|url=http://www.livescience.com/51455-women-outlive-men.html|access-date=2015-07-08}}</ref> Most of the difference in life expectancy between the sexes is accounted for by differences in the rate of death by cardiovascular diseases among persons aged 50–70.<ref name="pmid26150507">{{cite journal|vauthors=Beltrán-Sánchez H, Finch CE, Crimmins EM|title=Twentieth century surge of excess adult male mortality|journal=Proceedings of the National Academy of Sciences of the United States of America|volume=112|issue=29|pages=8993–8|date=July 2015|pmid=26150507|pmc=4517277|doi=10.1073/pnas.1421942112|doi-access=free|bibcode=2015PNAS..112.8993B}}</ref>