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The first online-only news site in state history to get media credentials to cover the state capitol and Seattle city hall, PubliCola has been called a “must-read” by the Seattle Post Intelligencer and a hot “New Media Mover and Shaker” by Seattle Magazine—which also cited our own Erica C. Barnett as the city's No. 1 news nerd.

Correlation Isn’t Causation, But…

On Other Blogs   January 18, 2012 at 2:46 pm Erica C. Barnett

The correlation between diabetes and obesity rates on the one hand, and sedentary lifestyles/car commuting on the other, is certainly fascinating.

Two researchers at Planetizen created county-by-county maps of diabetes, obesity, and car-commuting rates across the United States, and found that the former two conditions correlate strongly with the latter, with diabetes, obesity, and car commuting, including carpools, most prevalent in the Southeast US and Appalachia.

First, obesity:

Diabetes:

And commute modes, with higher percentages of people who drive to work represented in yellow, orange, and red.

Similarly, the rates of biking and walking to work tend to be inversely proportional to obesity and diabetes rates, and higher median incomes and education levels correlate to lower rates of obesity and diabetes. In general. As Planetizen notes,

Although this map does not look exactly the same as the obesity and diabetes maps, there are some striking similarities. Throughout the Appalachians and the deep South, there is a pattern that we could call the “non-active transportation belt,” where the percentages of commuters who drive are highest. It covers a similar area to the “diabetes belt,” but also extends somewhat into Indiana, Ohio, and Michigan. Considering that one-third of the higher diabetes risk associated with living in the diabetes belt can be attributed to the modifiable risk factors of sedentary lifestyle and obesity, this map certainly suggests that commute mode may play an important part in the existence of the diabetes belt.

Interestingly, unemployment is the one negative factor Planetizen looked at that does not correlate with obesity. And, again, correlation does not necessarily imply causation. Obesity and diabetes rates among residents of the Appalachians and Deep South could be impacted just as heavily by factors like lack of access to fresh food, stress, regional culture, and sedentary hobbies as they are by the fact that those residents are more likely to drive. Still, the correlation definitely a part of the story.

Commuting statistics are from the Census Bureau, and obesity and diabetes stats are from the Centers for Disease Control.

 


  • Anonymous

    >> The correlation between diabetes and obesity rates on the one hand, and sedentary lifestyles/car commuting on the other, is certainly fascinating.

    The correlation between activist journalists and cherry-picked data which matches their worldview or agenda, is certainly fascinating.

  • Anthony

    I strongly advocate for increased “alternative” mode transportation like cycling, walking, and transit through improved land use and the transfer of government funds from roads to transit, but I have to agree with Reality_Guy on this one.

    It makes sense that a sedentary lifestyle exasperated by increased driving can lead to obesity, but the data chosen to make the point is incomplete at best and misleading at worst.  At least the story is prefaced with the disclaimer that correlation does not equal causation, though looking at the maps there doesn’t even seem to be much correlation outside of the southern states.  Of course you could cherry-pick counties to make an argument, but I’m looking at Clark County, Washington (Vancouver), Connecticut/Rhode Island, and Alaska. 

    At a glance, this appears to be a correlation based on geography and culture [food, weather, etc] more than by driving habits. 

  • repete

    “researchers”  my ass.

  • Verd1n

    The better correlation more likely lies with these health issues and football.  Check out the line backers on the SEC squads.

    Hell, it may even have more to do with education vs chopping cotton and coal mining.

  • Limes

    The frustration here is that the categories for the transportation map are misleading.  The first category is from 0-86, while the others only show a 1 or 2 percentage points.  Generally, the US is a driving country.  The differences among the commuting map are skewed and should not be seen as valid.  

    And finally, there is also a correlation between diabetes and people of color, particularly African American.  I see that is not as discussed here.

  • FrequentPoster

    Given that the author of this article is the one and only, the notorious Erica “Fact-Free” Barnett, I think I’ll sit back for a while to see what facts other people show that she’s mangled, ignored, misrepresented, or outright lied about.

  • Bark More Wag Less

    I see lots of fat people on the bus the few times I take it every year.

  • Dubba love

    News flash: black people are really fat. They live in rural southern areas without realistic public transit.

    Wait, what?

  • it’s exercise, not driving

    caloric output is the causal factor:  many drivers put out lots, during the part of the day not driving, and many nondrivers don’t put out many calories they’re walking a bit more to be sure but not all that much, just to the store, and to the bus stop to go to work.  most nondrivers are not walking up steep hills twice a day like some seattleites, they’re sitting at a bus stop in st. louis while eating fatty food and they don’t get hardly any exercise.  iow it’s quite obviously the choice to exert calories or not that is the causal factor in being fat — not whether you drive to work.  I don’t drive to work, I work at home, so how does that mean I spend more calories getting to work?  When I drive to go on a 50 mile bike ride, thought, I am a driver who’s outputting tons of calories — quite a bit mor than most people can even output.  driving has enough costs and externalities without making stuff up.  the key externality cost relevant here would be that pro sprawl planning choices mean people walk less in general, thy don’t walk to the store.  if you’re in the top half though, you probably get exercise and it doesn’t matter.  if you’re poor, you probably don’t.  But lots of that is your choice.  Just not having a car doesn’t mean you’re more likely to be skinny, transit agencies are all recalculating the width of the average seat, it’s not because “transit users tend to be skinnier” in general is it. if you’re talking health, obviously the lowest quintile is way more pro tobacco and that both increases disease and discourages exertion so it’s a real killer, and it is not really related to driving, although I guess poverty lack of education and lack of taking initiative in general can “cause” both the choice to smoke nad the choice to not get exercise, that is, the choice to be fat.

  • Theo Chernoff

    People in the south are fatter because of a diet filled with fried foods and cheap fatty cuts of meat. Lived there for 10 years.

    Besides – your “correlation” discounts the simple idea that commuting by mass transit, at least in our area usually keeps you on your ass longer than driving does.

  • Snoman

    Your mom rides the bus?

  • Just Saying

    A huge percentage of those southern fatties are blacks.

  • ceryous

    What’s up with Alaska? Those obese, diabetes free, carpoolers.

  • Kidforlife73

    Once again, it’s paragraph man to the rescue with his keen insight.

  • Kidforlife73

    How about those skinny, diabetes free, carpoolers in Hawaii.

  • return provided

    kid:  when I see dialogue here at a level that’s worth my time to do further editing, I will do further editing.    Oh wait, I mean this [hits return] 

    But for folks like you? I just don’t respect you enough.

  • Alex Mandel

    The colors are not distributed evenly along the ranges. You see that green is 28.4% obese and red is 31.6% Though the driving mode share only varied by about 15% also, from ~80-95%, it’s still not a great presentation of the data. It’s hard to tell if there are not negative correlations in the green regions.