(www.improvingmedicalstatistics.com)                                          
     
home   author    contact   web site dedication
  

         

......................m.........................

Specific guide to this web site for:


 1.  Medical School
      Educators 
      in Statistics


 2.  Medical Students

 3.  Science media writers

 4.  High School & College
     Statistic Teachers


   Misadventures:


1. Harvard led MI study

2. JACC study 

   (J. of Amer. Coll.
   Cardio.)


3. NEJM cath study

4. Amer. J. of Cardio.
    review of literature

5.
ALLHAT
    controversy
 

6.
Oat bran study

7.
Pregnancy & Alcohol

8.
Are Geminis really
   
different?
      
9. Columbia 'Miracle' Study  
                                                 

Additional Topics:

Celebrex

Limitations of Meta-Analyses

Large Randomized Clinical Trials

Tale of Two Large
Trials

Advocate meta-analyses

Network meta-analyses






 

 

 



Critique of the meta-analysis written by the senior author of the initial flawed oat bran study:

  The conclusions of a meta-analysis (a summation of similar clinical trials), like any other study, can be presented with a particular slant. There is a tendency for any person to desire to confirm prior opinions voiced in the literature rather than refuting their own prior results.

 A subsequent meta-analysis1 concerning the effects of oat bran on cholesterol levels was written by the senior author of the widely publicized study2 that incorrectly suggested oat bran and wheat bran supplements "reduce serum cholesterol about equally" and that "oat bran has little cholesterol lowering effect."   The conclusions of this subsequent meta-analysis were presented in such a way as to minimize any contradictions with the initial flawed study published in 1990.

1. Brown L, Rosner B, Lillett W, Sacks F. Cholesterol-lowering effects of dietary fiber: a meta-analysis. Am. J. Clin. Nutr. 1999; 69:30-42

2. Swain JF, Rouse,IL, Curley CB, Sacks FM.  Comparison of the effects of oat bran and low-fiber wheat on serum lipoprotein levels and blood pressure. N Engl J Med 1990; 322:147-52.


Differing conclusions for the data from the same meta-analysis:

The negatively slanted conclusions of the original authors are followed by an alternative version with positively slanted conclusions for the same meta-analysis evaluating soluble fiber.
   
"print format"

The results of the meta-analysis1 by the authors of the flawed oat bran study can be viewed as a cup half full or half empty, depending on the bias of the authors.  

 Negative viewpoint of the original authors

The authors of this meta-analysis1 conclude that "increasing soluble fiber can make only a small contribution to dietary therapy to lower cholesterol." 

They note that soluble fiber from three bowls (28g) of oatmeal is required to achieve even a 3 g soluble fiber intake. (Ingestion of 3g of soluble oat fiber resulted in a decrease of .13mmol/L in total cholesterol.)

 Alternative positive viewpoint

An alternative positive statement of the conclusions for the same data from the same meta-analysis would be the following: 
  
This meta-analysis suggests that an intake of 3g of oat soluble fiber daily can result in a 2% reduction in  cholesterol which has been estimated to correlate to a 4% reduction in cardiovascular disease2. Similarly, an intake of 6g of fiber would result in a 4% reduction in cholesterol which is estimated to result in an 8% reduction in cardiovascular disease2. This would be a significant public health benefit. 

(Additional details in the alternative positive viewpoint would include the following. It would be noted that a single standard 40g serving of oatmeal of Quaker Oats Old Fashioned Oatmeal contains 2g of soluble fiber and a single 40g standard serving of Quaker Oat Bran hot cereal contains 3g of soluble fiber/serving.)
_________________________ 

Both versions of these conclusions are slanted, but in opposite directions.

The positive and negatively slanted viewpoint presented the following findings of the meta-analysis in very different ways.
The results of the meta-analysis indicated that 3g of soluble fiber can result in a decrease cholesterol of 13mmol/L (5mg/dL), while 6 g of soluble fiber can result in a decrease of cholesterol of 26mmol/L (10mg/dL). The positively and negatively framed conclusions had very different ways of interpreting this same data.

See:  Limitations of meta-analysis for further information.

_________________________ 

1. Brown L, Rosner B, Lillett W, Sacks F. Cholesterol-lowering effects of dietary fiber: a meta-analysis. Am. J. Clin. Nutr. 1999; 69:30-42

2. National Cholesterol Education Program Expert Panel on Detection, Evaluation and Treatment on High Blood Cholesterol in Adults. Report of the National Cholesterol Education Program Expert Panel.  Arch Intern Med 1988;148:36-9

Additional details  

 

 

 

 

 

 

 

 

 

 

 

Hit Counter

copyright 2005-2013   ImprovingMedicalStatistics.com