The “Graying” Population and Life Expectancy

The term “graying of America” refers to the fact that the American population is steadily becoming more dominated by older people. In other words, the median age of Americans is going up.^[1] According to the U.S. Census Bureau’s 2017 National Population Projections (Figure 1), the year 2030 marks an important demographic turning point in U.S. history. By 2030, all baby boomers will be older than age 65. This will expand the size of the older population so that 1 in every 5 residents will be retirement age. And by 2035, it’s projected that there will be 76.7 million people under the age of 18 but 78 million people above the age of 65. ^[2]

The 2030s are projected to be a transformative decade for the U.S. population. The population is expected to grow at a slower pace, age considerably and become more racially and ethnically diverse. Net international migration is projected to overtake natural increase in 2030 as the primary driver of population growth in the United States, another demographic first for the United States.

Although births are projected to be nearly four times larger than the level of net international migration in coming decades, a rising number of deaths will increasingly offset how much births are able to contribute to population growth. Between 2020 and 2050, the number of deaths is projected to rise substantially as the population ages and a significant share of the population, the baby boomers, age into older adulthood. As a result, the population will naturally grow very slowly, leaving net international migration to overtake natural increase as the leading cause of population growth, even as projected levels of migration remain relatively constant.^[3]

“Graying” Around the World

While the world’s oldest countries are mostly in Europe today, some Asian and Latin American countries are quickly catching up. The percentage of the population aged 65 and over in 2015 ranged from a high of 26.6 percent for Japan to a low of around 1 percent for Qatar and United Arab Emirates. Of the world’s 25 oldest countries, 22 are in Europe, with Germany and Italy leading the ranks of European countries for many years.^[4]

By 2050, Slovenia and Bulgaria are projected to be the oldest European countries. Japan, however, is currently the oldest nation in the world and is projected to retain this position through at least 2050. With the rapid aging taking place in Asia, the countries of South Korea, Hong Kong, and Taiwan are projected to join Japan at the top of the list of oldest countries and areas by 2050, when more than one-third of these Asian countries’ total populations are projected to be aged 65 and over.^[5]

Life Expectancy

Life expectancy is a statistical measure of the average time an organism is expected to live, based on the year of birth, current age and other demographic factors including gender. The most commonly used measure of life expectancy is at birth (LEB). There are great variations in life expectancy in different parts of the world, mostly due to differences in public health, medical care, and diet, but also affected by education, economic circumstances, violence, mental health, and sex.

Life Expectancy vs Lifespan

Lifespan or Maximum Lifespan is referred to as the greatest age reached by any member of a given population (or species). For humans, the lifespan is currently between 120 and 125. Life Expectancy is defined as the average number of years that members of a population (or species) live. According to the World Health Organization (WHO)^[6] global life expectancy at birth in 2015 was 71.4 years, with females reaching 73.8 years and males reaching 69.1 years. Women live longer than men around the world, and the gap between the sexes has remained the same since 1990. Overall life expectancy ranged from 60.0 years in the WHO African Region to 76.8 years in the WHO European Region. Global life expectancy increased by 5 years between 2000 and 2015, and the largest increase was in the WHO African Region where life expectancy increased by 9.4 years. This was due primarily to improvements in child survival and access to antiretroviral medication for the treatment of HIV. According to the Central Intelligence Agency^[7] the United States ranks 43rd in the world for life expectancy.

Gender Differences in Life Expectancy

Biological Explanations

Biological differences in sex chromosomes and different pattern of gene expression is theorized as one reason why females live longer.^[8] Males are heterogametic (XY), whereas females are homogametic (XX) with respect to the sex chromosomes. Males can only express their X chromosome genes that come from the mother, while females have an advantage by selecting the “better” X chromosome from their mother or father, while inactivating the “worse” X chromosome. This process of selection for “better” genes is impossible in males and results in the greater genetic and developmental stability of females. In terms of developmental biology, women are the “default” sex, which means that the creation of a male individual requires a sequence of events at a molecular level.

Men are more likely to contract viral and bacterial infections, and their immunity at the cellular level decreases significantly faster with age. Although women are slightly more prone to autoimmune and inflammatory diseases, such as rheumatoid arthritis, the gradual deterioration of the immune system is slower in women.^[9][10]

Looking at the influence of hormones, estrogen levels in women appear to have a protective effect on their heart and circulatory systems.^[11] Estrogens also have antioxidant properties that protect against harmful effects of free radicals, which damage cell components, cause mutations, and are in part responsible for the aging process. Testosterone levels are higher in men than in women, and are related to more frequent cardiovascular and immune disorders. The level of testosterone is also responsible, in part, for male behavioral patterns, including increased levels of aggression and violence.^[12][13] Another factor responsible for risky behavior is the frontal lobe of the brain. The frontal lobe, which controls judgment and consideration of an action’s consequences, develops more slowly in boys and young men. This lack of judgment affects lifestyle choices, and consequently many more boys and men die by smoking, excessive drinking, accidents, drunk driving, and violence.^[14]

Lifestyle Factors

Certainly not all the reasons women live longer than men are biological. As previously mentioned, male behavioral patterns and lifestyle play a significant role in the shorter lifespans for males. One significant factor is that males work in more dangerous jobs, including police, firefighters, and construction, and they are more exposed to violence. According to the Federal Bureau of Investigation^[15] there were 11,961 homicides in the U.S. in 2014 (last year for full data) and of those 77% were males. Males are also more than three times as likely to commit suicide.^[16] Further, males serve in the military in much larger numbers than females. According to the Department of Defense,^[17] in 2014 83% of all officers in the Services (i.e., Navy, Army, Marine Corps and Air Force) were male, while 85% of all enlisted service members were male.

Additionally, men are less likely than women to have health insurance, develop a regular relationship with a doctor, or seek treatment for a medical condition.^[18] As mentioned in the middle adulthood chapter, women are more religious than men, which is associated with healthier behaviors.^[19] Lastly, social contact is also important as loneliness is considered a health hazard. Nearly 20% of men over 50 have contact with their friends less than once a month, compared to only 12% of women who see friends that infrequently.^[20] Overall, men’s lower life expectancy appears to be due to both biological and lifestyle factors.

Sexuality