Example of problems with self-report data: reported differences in BMI in the US

[Dolphin]

Lay article on this:

Does this state make my butt look big?
http://healthjournalism.org/blog/2013/04/does-this-state-make-my-butt-look-big/#more-19270

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Abstract:

The geographic distribution of obesity in the US and the potential regional differences in misreporting of obesity.


Obesity (Silver Spring). 2013 Mar 20. doi: 10.1002/oby.20451. [Epub ahead of print]

Le A, Judd SE, Allison DB, Oza-Frank R, Affuso O, Safford M, Howard VJ, Howard G.

Source
Department of Biostatistics, UAB School of Public Health, Birmingham, AL.

Abstract

OBJECTIVE:

State-level estimates of obesity based on self-reported height and weight suggest a geographic pattern of greater obesity in the Southeastern US; however, the reliability of the ranking among these estimates assumes errors in self-reporting of height and weight are unrelated to geographic region.

DESIGN AND METHODS:

We estimated regional and state-level prevalence of obesity(body mass index ≥ 30 kg/m2 ) for non-Hispanic black and white participants aged 45 and over were made from multiple sources:

1) self-reported from the Behavioral Risk Factor Surveillance System (BRFSS 2003-2006) (n = 677,425),

2) self-reported and direct measures from the National Health and Nutrition Examination Study (NHANES 2003-2008) (n = 6,615 and 6,138 respectively),

and

3) direct measures from the REasons for Geographic and Racial Differences in Stroke (REGARDS 2003-2007) study (n = 30,239).

RESULTS:

Data from BRFSS suggest that the highest prevalence of obesity is in the East South Central Census division; however, direct measures suggest higher prevalence in the West North Central and East North Central Census divisions.

The regions relative ranking of obesity prevalence differs substantially between self-reported and directly measured height and weight.

CONCLUSIONS:

Geographic patterns in the prevalence of obesity based on self-reported height and weight may be misleading, and have implications for current policy proposals.

Copyright © 2013 The Obesity Society.

PMID: 23512879 [PubMed - as supplied by publisher]

 

[Esther12]

Thanks.

I wonder what results we would get if we were to randomize a group of obese people into two groups, one of which was told that obesity was a result of their behaviour and something they could and should control and that failure to do so indicates mental health problems which need treating; and one of which was told that obesity was largely a result of genetics and hormonal factors which were poorly understood and largely outside of their control - and both groups were asked to self-report their weight immediately after the talk. My suspicion is that this psychosocial education would lead to significant self-reported weight loss.

Actually, I think Wessely may have approvingly cited a similar study:

Additional, although indirect evidence on the impact of illness perception comes from a recent trial in which conversion disorder patients improved when told that full recovery constituted proof of a physical aetiology, whereas non-recovery would constitute proof a psychiatric origin (Shapiro & Teasell, 2004).

The Wessely paper is available here: simonwessely.com/Downloads/Publications/CFS/179.pdf

I've still not read the cited paper... it's on my list of things to do.

 

[Calathea]

For starters, your weight will come out differently depending on whether you're taking it or your doctor is taking it. People who are taking their weight at home tend to do so first thing in the morning, after going to the toilet but before eating, without any clothes on, because that's when it's lowest, and also that's when it's a more stable number. Doctors weigh you in the middle of the day, clothed, after you've eaten a meal or two.