[Relation between body fat distribution, insulin levels and glucose tolerance in obese females]

Selecting the language of the publications included in a meta-analysis: is there a Tower of Babel bias?

Although they usually claim a very thorough search to retrieve every pertinent work, most meta-analyses published in English restrict their search to papers which were also published in English. We reviewed all the meta-analyses printed from 1 January 1991 to 1 April 1993 in 8 medical journals published in English and selected those who stated linguistic restrictions for inclusion in the analysis. The computerized search methods used in these meta-analyses were then duplicated looking specifically for publications written in the excluded languages. Each meta-analysis was then redone with identical statistical tests to determine if its conclusions would have been different if the paper(s) absent only for linguistic reasons had been included. A total of 36 meta-analyses of which 28 had language restrictions were identified. The computer searches yielded 19 papers scientifically acceptable but excluded for linguistic reasons. Eleven of these articles were retained as having the potential to modify their corresponding 7 meta-analyses. One meta-analysis which concluded that selective decontamination of the digestive tract in intensive care units did not produce a significant change in mortality between treatment and control patients (OR 0.70; 95% CI 0.45-1.09) would have arrived at a different conclusion (OR 0.67; 95% CI 0.47-0.95) if a paper written in German in a Swiss journal had been included in the analysis. Our study demonstrates that, in at least one out of 36 consecutive meta-analyses the exclusion of papers for linguistic reasons produced results different from those which would have been obtained if this exclusion criteria had not been used.

Therapy-resistant hypertension associated with central obesity, insulin resistance, and large muscle fibre area

Obesity and an enhanced insulin response to oral glucose tolerance test are associated with therapy resistance in hypertension. In order to explore this association further we studied the insulin sensitivity of subjects with essential hypertension resistant to triple drug therapy (RH), with the euglycemic insulin clamp technique. Well controlled hypertensives, matched for age, gender and body mass index (BMI) served as controls. Male subjects (7 RH and 7 controls) were further investigated by biopsies of Musculus Vastus lateralis since structural conditions in skeletal muscles might have a role in the above association. Irrespective of pre-study drug therapy, therapy-resistant hypertensives had a lower insulin sensitivity index than controls (p < 0.05). In spite of the BMI-match waist/hip ratio (WHR) in the RH males tended to be higher (p < 0.07). Insulin clearance tended to be lower in RH subjects (p = 0.09). BMI correlated with a reduced muscular capillary density (r = -0.77, p < 0.01). The average cross-sectional muscle fibre area was larger in RH subjects (p < 0.05). The mean muscle fibre area correlated with basal serum insulin (r = 0.63; p < 0.05). Rarefaction of the muscular capillary bed appears to be related to obesity. Larger muscle fibres might be an effect of the growth factor properties of insulin and could possibly correspond to hypertrophy of smooth muscle in the resistance vessels. This factor might contribute to the association of hyperinsulinemia and hypertension and attenuate the response to antihypertensive therapy.