Table 3 Association of the frailty index (FI) with the risk of dementia in complete DZ and MZ twin pairs in the within-pair sample in the multivariate Cox model (left panel) and the within-pair model (right panel). Hazard ratios (HRs) and 95% confidence intervals (CIs) are presented for a 10% increase in FI

FI

1.23 (1.15, 1.31)*

1.12 (1.00, 1.25)*

1.24 (1.12, 1.37)*

1.13 (0.91, 1.42)

Age at FI measurement

1.15 (1.14, 1.16)*

1.14 (1.12, 1.15)*

1.17 (1.16, 1.18)*

1.18 (1.16, 1.20)*

Male sex

0.83 (0.74, 0.94)*

0.87 (0.70, 1.08)

0.77 (0.65, 0.92)*

0.89 (0.68, 1.17)

Education years

0.97 (0.95, 0.99)*

0.96 (0.93, 0.99)*

0.97 (0.93, 1.00)

0.97 (0.89, 1.04)

Tobacco user

1.13 (1.00, 1.27)*

1.28 (1.04, 1.57)*

1.17 (0.96, 1.41)

0.78 (0.51, 1.18)