The difference in prevalence between the two populations was greatest for TTH.
There were also no differences in prevalence between zygosity groups or between twins and their singleton siblings.
The two-fold difference in prevalence between genders remained stable in employed participants with a workday yesterday (women 16.4%, men 7.5%).
Frequency of sexual intercourse or Valsalva maneuver as triggers did also not differ in prevalence between ETM and non-ETM group.
Fisher's exact test was used to test for differences in prevalence between the treatment groups.
Hence, our conclusion about the change in prevalence between surveys holds with or without the statistical adjustments.
However, a wider gap in prevalence between rural and urban areas could be observed in some age groups by 2006.
In the current study, important variations in prevalence between surveys were observed and cannot be explained by any of the factors included in this analysis.
Evidence for genetic risk includes familial aggregation [5], [7] and differences in prevalence between ethnic groups [8] [10] (caucasians of Northern European ancestries appear to be particularly susceptible).
The evidence of prevalence of this mutation is patchy with few studies looking at this locus and those that have show considerable differences in prevalence between countries.
We tested for significant differences in prevalence between island and mainland populations using Fisher's exact test, since all comparisons involved cells with low values.
