Table 3.

Cox regression for time to death as a function of FI₃₄ or age in the Louisiana Healthy Aging Study (LHAS)

Variable	β	Exp (β)	P value	R2	Wald test P
FI34	2.358a	10.570a	0.0042	0.040	0.00416
Age	0.01695	1.017	0.124	0.014	0.124

FI₃₄ frailty index based on 34 items

^aThe coefficient (β) and its exponentiated value (Exp (β)) are for a unit increase in FI₃₄. FI₃₄ scores range from 0 to 1, but a FI₃₄ score of 1 is practically impossible. Therefore, to better estimate the effect of the covariate, we should compute the values for a fractional increase, i.e., 0.1 rather than the whole unit (1). In this case, e^{(0.1 · β)} = 1.27, which means an increase in the hazard by 27 % for a tenth of the unit increase in FI₃₄