Question

Prevalence-incidence bias occurs:

a.The exposure is associated with a decrease in both the incidence and prevalence of disease

b.Most commonly in cross-sectional studies

c.The outcome has an influence on the duration of disease

Answer 1

Prevalence Incidence bias is a limitation of the cross-sectional studies. The bias is based on the fact that cross-sectional studies are maily based on the prevalence and they look at prevalence of the disease by exposure groups. It means that cross-sectional studies emphasise on finding whether exposure increases prevalence of the disease.

Prevalence = Incidence x Duration

Now if prevalence of a given disease is higher in the exposed group than the unexposed group, it can not be determined that whether exposure is higher due to incidence or is due to the duration.

If we wish to know whether exposure is related to higher incidence of the disease the equation becomes limited as it does not distinguishes between exposure causing higher incidence of the disease or exposure affecting duration of diseas (making the disease longer or shorter).