Table 2.
Causal mediation analysis of the association of SES and ADL impairment mediated by social isolation at 18 and 36 months of follow-up
| Socioeconomic status | Effect | ORa | 95% CI | RDa | 95% CI | Age groupb |
|---|---|---|---|---|---|---|
| 18 months of follow-up | ||||||
| Education | Natural direct effect | 1.05 | 0.35–3.11 | 0.01 | − 0.16 to 0.18 | 70 + |
| Education | Natural indirect effect | 1.00 | 0.96–1.04 | 0.00 | − 0.01 to 0.01 | 70 + |
| Education | Total effect | 1.05 | 0.35–3.14 | 0.01 | − 0.17 to 0.18 | 70 + |
| Education | Natural direct effect | 2.87 | 0.97–8.45 | 0.24 | 0.00 to 0.48 | 80 + |
| Education | Natural indirect effect | 1.01 | 0.96–1.06 | 0.00 | − 0.01 to 0.02 | 80 + |
| Education | Total effect | 2.90 | 0.98–8.59 | 0.25 | 0.00 to 0.49 | 80 + |
| Income | Natural direct effect | 1.51 | 0.73–3.11 | 0.07 | − 0.07 to 0.21 | All |
| Income | Natural indirect effect | 1.00 | 0.95–1.05 | 0.00 | − 0.01 to 0.01 | All |
| Income | Total effect | 1.50 | 0.74–3.06 | 0.07 | − 0.07 to 0.20 | All |
| Jobc | Natural direct effect | 1.14 | 0.56–2.33 | 0.03 | − 0.10 to 0.15 | All |
| Job | Natural indirect effect | 1.00 | 0.97–1.03 | 0.00 | 0.00 to 0.00 | All |
| Job | Total effect | 1.14 | 0.56–2.33 | 0.03 | − 0.10 to 0.15 | All |
| 36 months of follow-up | ||||||
| Education | Natural direct effect | 1.22 | 0.48–3.15 | 0.02 | − 0.14 to 0.17 | 70 + |
| Education | Natural indirect effect | 0.99 | 0.94–1.03 | 0.00 | − 0.01 to 0.01 | 70 + |
| Education | Total effect | 1.21 | 0.47–3.09 | 0.02 | − 0.14 to 0.17 | 70 + |
| Education | Natural direct effect | 0.34 | 0.10–1.16 | − 0.29 | − 0.56 to 0.02 | 80 + |
| Education | Natural indirect effect | 0.99 | 0.95–1.04 | 0.00 | − 0.01 to 0.01 | 80 + |
| Education | Total effect | 0.34 | 0.10–1.15 | − 0.29 | − 0.56 to −0.02 | 80 + |
| Income | Natural direct effect | 1.67 | 0.81–3.44 | NAd | NA | All |
| Income | Natural indirect effect | 0.94 | 0.86–1.02 | NA | NA | All |
| Income | Total effect | 1.56 | 0.75–3.25 | NA | NA | All |
| Job | Natural direct effect | 1.99 | 0.94–4.20 | NA | NA | All |
| Job | Natural indirect effect | 1.04 | 0.97–1.11 | NA | NA | All |
| Job | Total effect | 2.07 | 0.98–4.40 | NA | NA | All |
95% CI 95% confidence interval, RD risk difference, OR odds ratio
aThe effect estimates of OR and RD could be interpreted as the effect from the top to the bottom of the social gradient
bResults were stratified by age where the interaction term between SES and age was significant. Age at baseline were broken down into two groups—“70 +” means aged 70–79 and “80 +” means those who were aged 80 or above
cJob refers to the longest held occupation in lifetime as in the main text
dSome results for the natural effect model using linear probability model showed as “NA”, since the model did not converge