Because marital status and educational level are categorical variables without a linear trend, we set dummy variables for the two variables respectively.
The time of FA supplement was calculated by setting the dummy variable.
Finally, we extent the model by two sets of dummy variables covering policy regimes.
The highest level of secondary education completed is measured by a set of dummy variables, distinguishing respondents who have either no completed degree in secondary education or a special education degree (=1), a lower secondary education degree (=2), a degree of higher secondary education in a vocational track (=3) or a degree in a general or academic higher secondary level (=4).
Third, physical activity was summarized by a set of dummy variables indicating, respectively, the frequency (never or hardly ever, 1 3 times a month, once a week, more than once a week) of vigorous (mainly playing sports) and moderate (gardening, cleaning the car, or going for a walk) activities.
Thus, we alternatively estimated OR 10, OR 01 and OR 11 and their p values by setting up three exclusive dummy variables V10, V01 and V11 (without interaction term) in the regression equation: V10 =1 if E = 1 and G = 0; V01 = 1 if E = 0 and G = 1; and V11 = 1 if E = 1 and G = 1, while considering V00 (E = 0 and G = 0) as the reference group.
Finally, we have analysed whether the likelihood of a move depends on the time already spent in the unskilled occupation by means of a set of dummy variables that identify durations in the unskilled occupation which are shorter than 1 year, between 1 and 5 years and longer than 5 years.
Finally, health services use was measured by the self-reported number of hospital visits (a set of dummy variables) and the number of claims-based physician visits (excluding emergency department encounters), both during the year prior to baseline.
A separate dummy variable for these observations was added to the set of dummy variables which the occupational class consists of.
The ChEI agents were coded as a set of dummy variables.
