Table 1.

Proxy measures of cognitive reserve.

Indicator	Description and categories
Education	Four aggregate categories: none attained; low (5 to 9 years, pre-primary—intermediate); medium (12 years, secondary), and high (university or vocational training).
Occupation	1st categorization (2 levels): Currently employed or unemployed. 2nd categorization (5 levels): Complexity of highest ranked attained occupation: 0: never employed, 1: elementary occupations, 2: skilled and semi-skilled occupations, 3: services, technical, and associate professional occupations, and 4: managerial and professional occupations.
Current Physical Activity	1st categorization (4 levels): no activity beyond baseline activities of daily living (0 MET-min), low physical activity (1–499 MET-min), medium physical activity (500–999 MET-min) and high physical activity (≥1,000 MET-min). 2nd categorization (2 levels): active (low, medium, or high) or inactive (no activity).
Current Social Activity	Social integration: Frequency of social group meeting attendance were summed. No involvement was recorded as 0, occasional as 1, and regular as 2. The maximum score is 4, with higher scores indicating higher social integration levels (0–1 = most isolated; 2 = moderately isolated; 3 = moderately integrated; and 4 = most integrated). Social network size: represented by the average of number of children, relatives, friends, neighbors, and presence or absence of a spouse (presence = 1; absence = 0). Social network function: the rates of contact with family, friends, and neighbors (0 = never; 1 = less than 1 time per month; 2 = at least monthly; 3 = at least weekly; 4 = two to three times per week; 1 = daily) were summed. A composite score of social activity was derived by summing up the three indicators. Interquartile ranges were calculated to categorize the scores into three groups (low, medium, high).