Parametric and non-parametric methods to estimate the pattern of the age at natural menopause based on prevalence data

Various studies have shown the age changes of menopause in Iran, in a relatively wide area, approximately from 46 to 51 years. This broad range of the changes can attribute not only to the essential difference between women of different regions, but could also be related to methodological problems. Because the model of menopause age could be estimated by cohort or a cross-sectional survey; that each has advantages and disadvantages. On a special type of cross-sectional studies, the target is only the status of menopause for each woman, such that the prevalence of menopause can be calculated in each age group. Therefore, how one can estimate the pattern of the age at menopause using the prevalence data?

For estimating the patterns of the age at natural menopause and its characteristics, parametric and non-parametric methods are introduced and the data from the survey:" Estimating the pattern of the age at natural menopause and its effective factors in Semnan" are used to illustration of the methods. In that survey, during the year 2007, Total number of 3545 urban and rural women were randomly selected and their status in terms of menopause or not asked, then by excluding abnormal menopause, 3404 of whom have participated in the study. Finally, it was determined which procedure provides better natural menopause age model.

The pattern of menopause age obtained with the help of generalized linear models (GLM) with parametric base and non-parametric method in which the probability distribution is estimated empirically. Although there were not many differences between the estimated values in the different models, but the log - log model had greater estimation than two-parametric, logistic and probit, models and its results were more like non-parametric model. Among parametric models, logistic model had the best fitting.

It seems, logistic model is more appropriate than other models to estimate the pattern of the age at natural menopause, although further research is needed.