Fig. 10

Predictions of the comorbidity index across age considering sub-populations characterized by different levels of education (low-high) and economic status (no economic problems-economic problems). The gray area represents the prediction interval at level 0.95. The comorbidity index refers to the one constructed using Equation (2) (i.e., maximum approach) and 2019 PASSI data (i.e., \(n= 31,746\) respondents). The educational variable takes the value as “low” if the respondent has an educational level below high school and “high” otherwise. The economic variable assumes the level “no economic problem” if the respondent makes ends meet with the financial resources available (from own or family income) very/quite easily and “economic problem” otherwise