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What is "life expectancy" and why should you care?

Put simply, life expectancy is the average number of years a person of any given age will live. Usually, people talk about life expectancy at birth – how many years can a person born in a specific time and place expect to live? For the U.S. overall, life expectancy at birth has increased DRAMATICALLY in the last 110 years, from 1900 when it was 47 up to 78 in 2010.

You can also calculate life expectancy at different ages: IF a person born in a given year lives to be 70, THEN how many more years will they, on average, live? We’ll come back to this later (HINT: longer!)

First, who cares about life expectancy? People do! Though we rarely think about it in exactly these math-y ways. We think about whether we’ll live to see our grandchildren grown or whether we’ll be able to complete big projects or realize dreams. Often, as individuals, we think about our own life expectancy in relationship to our loved ones and friends. Will I outlive my spouse? Everyone I know on my block? The colleagues I’ve always known? Because average life expectancy has increased so quickly, the people “exceeding expectations” in this project, have an average life expectancy nearly 25 years longer than their parents’ generation.

Governments look at life of expectancy to measure the health of populations in different times, places, and groups. It is one of those key measures we use to compare countries. Average life expectancy increases as counties become richer. However, countries have different patterns of life expectancy WITHIN them (as we do in NYC). Those differences are important indicators of differences in health and life opportunities between groups of people and different neighborhoods and environments. International organizations look for changes in life expectancy and its patterns as indicators of progress.

In New York City, in 2010, life expectancy at birth was 80.9. It rose 3 years from 2000. In NYC, life expectancy is higher than the U.S. overall and higher than other urban areas. Life expectancy is even different from one neighborhood to another. In NYC, life expectancy is HIGHER the less poverty in your neighborhood. A person born in a poor neighborhood in NYC can expect to live a little more than 79 years, but a person born in a neighborhood with little poverty can expect to live until over 83 years (on average).

There are also differences in average life expectancy for different racial/ethnic groups in NYC. It is HIGHEST for Hispanics; then non-Hispanic whites, and lowest for non-Hispanic African Americans. The difference is big: Hispanics have an average life expectancy at birth almost 5 years longer than African Americans. This is true despite more Hispanics living in poor neighborhoods so it’s a big effect.

WHY? People don’t know – one part of the answer is that people who immigrate to a new country tend to be healthier (on average) than the overall population. But so many NYC Hispanics are not immigrants themselves, so that isn’t the whole answer. There were not enough Asians across a range of ages to do the calculations for NYC. As for the other groups, these are complicated generalizations to make because people from so many very different places get lumped together as one racial/ethnic group.

Let's be clear, people do NOT think these different racial/ethnic groups are born with biological differences in life expectancy. These differences come from different individual and neighborhood life patterns – different levels of violence and accidents, exposure to infections (especially HIV), and diseases partly linked to behaviors – smoking, exercise, healthy eating, and misuse of drugs or alcohol. And it’s important to remember that all of these are PATTERNS of association—not 1:1 relationships at the level of the individual. So, on average, people who smoke are more likely to have cancers, heart disease, and lung disease and to die younger than people who do not smoke. This does not mean that any one specific, non- smoker will outlive any one specific smoker.

As hinted earlier, life expectancy can also be calculated at any given age. So people who are 40 in 2010 in NYC will, on average, live another 43.2 years if Hispanic, another 42.3 years if white/non-Hispanic, and another 39.6 years if African American/non Hispanic.

Most interesting for living while old is life expectancy at age 70. A person who was 70 in NYC in 2010 would, on average, live another 17 years! Some people think life expectancy at age 70 (or at age 65) is a better way to show healthy aging in a group or community than life expectancy at birth. Life expectancy at birth is strongly influenced by injuries and diseases that kill people early in life. But life expectancy at age 65 or 70 is influenced by how healthy people are in older age (produced by a combination of their life long resources, education, behaviors, environments, access to and quality of health care, and chance).

All numbers is this post came from a 2013 report by the New York City Department of Health and Mental Hygiene, which you can find here.


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