**2.1.2 IADL disability status**

There were five items in the instrumental activities of daily living (IADL) domain (shopping, finance, transportation, light housework, and telephone). Older adults were classified as having IADL disability if they reported any degree of difficulty or inability to perform on at least one item.

## **2.1.3 Covariates in Cox regressions**

Covariates were included in the Cox regression models according to their values in 1999. Age was categorical data, whereas sex, current working status, smoking habit, and alcohol ingestion were dichotomous data. Education was recorded as illiteracy or no formal education, elementary school, primary or senior high school, and college or beyond. Spouse status was recorded as either living with spouse (married or living together) or living without spouse (never married, divorced, separated, or widowed).

The exercise habit was divided into inactive (less than three times a week) and active (at least three times a week). Self-rated health was divided into healthier and worsening. The number of co-morbidities was counted from the list of hypertension, diabetes, cardiac disease, stroke, cancer, and arthritis. Cognitive function was measured with the modified Taiwan version of SPMSQ using nine items (range 0-9), correct answers were coded 1, whereas errors were coded 0, thus, higher SPMSQ score means better cognition performance, individuals were categorized as having normal (6 and above) or abnormal (5 and below) cognitive function (Yen et al., 2010). Symptoms of depression were assessed with the CESD, on which each of the 10 items is scored from 0 to 3. Individuals were categorized as not having (9 and below) or having (10 and above) depressive symptoms.
