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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

From: Frailty and the risk of dementia: is the association explained by shared environmental and genetic factors?

  Within-pair sample I
Multivariate Cox model Within-pair model
DZ twins
N = 11,031 pairs
MZ twins
N = 4055 pairs
DZ twins
N = 11,031 pairs
MZ twins
N = 4055 pairs
HR (95% CI) HR (95% CI) HR (95% CI) HR (95% CI)
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)
  1. *P < 0.05