Seattle - WA - BC life expectancyLife expectancy in the city of Seattle has positively soared over the last couple of decades!  Take a look:  in the early 1990s, residents of Seattle (the blue line) could expect a shorter average lifespan than the the state as a whole (the pink line).  But by 1997, Emerald City life expectancy shot ahead of the state average; and by the middle of the last decade it had even moved ahead of British Columbia. Today, if Seattle were an independent nation, its life expectancy would rank second in the world, just a month behind Japan’s.

A rapid rise in life expectancy is a big deal, since longer lives usually mean better health.  Both internationally and historically, populations that live longer tend to be healthier:  they suffer from fewer infectious diseases, face lower risks of injuries and catastrophic ailments, and have access to better medical care—the whole shebang. 

So Seattle’s rising life expectancy is clearly good news, but it’s also something of a puzzle.  What made Seattle get so healthy, so fast??

The good folks at Seattle / King County Public Health agency looked into things a bit, and came to at least one somewhat unexpected conclusion:  during the mid-1990s, the surprising rise in Seattle’s life expectancy could be attributed to the phenomenally steep decline in AIDS deaths.

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  • HIV mortality, King County and Washington

    Take a look at the chart to the right, showing HIV mortality among men and women in King County vs. Washington as a whole.  HIV deaths skyrocketed in the years leading up to 1996: among King County males aged 25-44, HIV was the leading cause of death from 1992 to 1996, accounting for 1,286 of the 3,539 deaths to males in this age group. And 77% of those King County HIV deaths were among residents of the city of Seattle proper.

    So the numbers suggest two things.  First, men in Seattle were particularly hard hit by the AIDS crisis.  Second, the rapid surge in Seattle life expectancy in the late 1990s—when Seattle overtook the state as a whole—can be traced first and foremost to the development of an effective treatment for HIV. Clearly, curbing the epidemic of AIDS fatalities was a huge boon to Seattle’s overall health.

    So that explains the life expectancy surge in the 1990s.  But it doesn’t explain health trends from 2000 to the present.  Why did Seattle improve so much faster than the region as a whole?  Are the trends real—or are they merely an artifact of a bad data?

    Life expectancy figures can be skewed in two ways—first, by mistaken population estimates; and second, by faulty or inconsistent ways of measuring fatalities.  We’ll know more about population figures when the 2010 census counts are released; perhaps the state has overestimated the increase in Seattle’s population, and hence underestimated death rates.  But the folks at Public Health can’t point to any significant changes in how death statistics are compiled—so there’s no obvious data anomaly that can account for Seattle’s striking rise in life expectancy.

    So perhaps, instead, Seattle’s life expectancy gains resulted from rising incomes.  All else being equal, wealthier people tend to be healthier people; so maybe a decline in poverty rates, or a sharp rise in median household earnings, was at the root of Seattle’s health advantage. The numbers, however, didn’t quite bear this out.  Seattle really has grown wealthier since 1990, and poverty grew a little slower in Seattle proper than in the state as a whole. But still, Seattle didn’t get that much wealthier; plus, poverty levels fluctuated quite a bit, and actually increased within city limits.

    So in the end, I’ve got a decent explanation for the 1990s rise, but I still have no solid answer to why Seattle’s life expectancy figures shot up so quickly since 2000, compared with the rest of state. 

    Any thoughts out there in blog land?


    [Data sources for this post include:

    • 1990-2008 Population Estimates: Population Estimates for Public Health Assessment, Washington State;
    • Department of Health, Vista Partnership, and Krupski Consulting.  January 2009.
    • Washington Department of Health

    Special thanks to Eva Wong and Myduc Ta, Public Health-Seattle & King County, for their assistance with data and for their fascinating analysis.]