This ecological study will be conducted using data from two sources. Data will be analysed from Global burden of disease (www.healthdata.org) for prevalence of male infertility and smoking for age groups >15 from year 2012-2019 and the data from Eurobarometer (www.europa.eu/eurobarometer/) on E-cigarettes usage of the same age groups and year under study. In the Eurobarometer database, electronic cigarette use is typically measured through survey questions that assess individuals' self-reported behaviours and attitudes towards e-cigarette use but they generally aim to gather information on the prevalence and patterns of e-cigarette use among the surveyed population. The following statistical analysis will be planned with the aggregated data. Employing a linear regression model with the male infertility prevalence as the dependent variable and the e-cigarette usage as the independent variable. Each data point in the model will represent a specific EU country during a particular year. A suitable regression method will be used to estimate the coefficients of the regression equation which will help establish the relationship between male infertility and e-cigarette usage rates, accounting for the variability across the EU countries. Furthermore, if other predictor variables at the country level are identified and data is available, they may be added to the regression model. This will help improve the estimation of coefficients and enhance the overall understanding of the relationship between male infertility and e-cigarette usage rates across EU countries.
The quality of the regression model will be examined by the goodness-of-fit measures. These metrics will indicate how well the model explains the variations in male infertility rates based on e-cigarette usage rates. The results of the linear regression analysis, including the significance and direction of the regression coefficients will determine if there is a statistically significant relationship between male infertility and e-cigarette usage rates among men aged >15 across the EU countries. Visualizations, such as scatter plots, to depict the relationship between male infertility prevalence rates and e-cigarette usage rates across the EU countries over the study period will be created. The results will be interpreted from the statistical analysis, including the strength, direction, and statistical significance of the regression.