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Saturday, July 25, 2015

The Tooth about Tobacco

If after reading Robert Allison's and Rick Wicklin's SAS blog posts on toothlessness you're saying "Yeah baby!, Yeah!" I want to read more, then you have come to the right place.

No one wants to lose their teeth, yet there is good chance this will happen to many people once they become senior citizens. One of the things in Rick's post was a correlation between median income in a state and the number of edentulous individuals. When I ran a proc corr against the data he provided, the relationship was -0.63442. Not bad, but I wondered if other variables were more highly correlated to toothlessness.

I wondered if instead of income, Body Mass Indicator or BMI might be more highly correlated to one losing teeth. Sure enough, as the below code and graph reveals, the correlation increased to 0.73565 using BMI as a variable.

data teethcig ;
  merge teeth cigs ;
  by state ;
run ;

proc corr 
  data = teethbmi 
  noprint 
  outp = opbmi( where = ( _type_ = 'CORR' and _name_ = 'BMI' ) )  ;
  var bmi pct ;
run ;

data _null_ ;
  set opbmi ;
  call symputx( 'BMICORR', put( pct, 8.5 ) ) ;
run ;

title "All Teeth Extracted vs. BMI";
footnote j = l "Source: http://www.cdc.gov/obesity/data/table-adults.html" ;
proc sgplot data = teethbmi ;
  scatter x = bmi y = pct / datalabel = state ;
  loess   x = bmi y = pct ;
  refline 18.5 / 
    axis = x 
    label = "Normal (18.5 - 24.99)"   
    lineattrs = ( color = red ) ;
  refline 25 / 
    axis = x 
    label = "Overweight (25 - 29.99)" 
    lineattrs = ( color = red ) ;
  refline 30 / 
    axis = x 
    label = "Obese (over 30)" 
    lineattrs = ( color = red ) ;
  xaxis values = ( 17.5 to 37.5 by 2.5 ) ;
  inset "Correlation Coefficient = &bmicorr" / 
    border 
    title = "Pearson" 
    position = bottomright ;
run ;

After looking at the output, I started to wonder if another variable such as tobacco usage might be more highly correlated to tooth loss than BMI. I was surprised to discover that the overall median adult cigarette smoking prevalence across states was 21.2% in 2011 using data provided by the Center for Disease Control or CDC. When cigarette smoking was correlated to toothlessness by state, the pearson correlation coefficient increased to 0.77286 as can be seen in the next graph.

Taking into consideration the usual caveat that correlation does not imply causation, if you want to retain your teeth it is likely best to avoid smoking, eat well, make more money and brush those chompers...

The full source code can be found here.