Table 3.

Results of Forward Selection Using a Set of Variables Which Includes Physical Activity Predictors Using 2 Different Stopping Rules Based on Improvement in Concordance (δC)

Stopping Rule: δC ≥ 0.01
Variable	Cumulative Concordance	δC	$\widehat{\beta }\pm 2\mathrm{S}\mathrm{E}(\widehat{\beta })$
Stopping Rule: δC ≥ 0.001
Age	0.681	0.681	0.096 (0.088, 0.104)
RA	0.720	0.038	−0.446 (−0.481, −0.411)
Age	0.681	0.681	0.086 (0.078, 0.094)
RA	0.720	0.038	−0.497 (−0.620, −0.374)
Self-reported overall health	0.729	0.009
Poor			0.581 (0.384, 0.778)
Fair			0.240 (0.123, 0.357)
Good			Ref.
Excellent			0.010 (−0.121, 0.141)
Cigarette smoking	0.734	0.005
Never			Ref.
Former			0.196 (0.100, 0.292)
Current			0.654 (0.506, 0.802)
Gender (male)	0.738	0.003	0.394 (0.297, 0.492)
Cancer	0.741	0.003	0.394 (0.263, 0.524)
Longstanding illness/disability	0.744	0.002	0.256 (0.153, 0.359)
TA	0.746	0.002	−0.328 (−0.453, −0.203)
Sedentary time, min	0.747	0.001	−0.003 (−0.005, −0.002)
Injury/illness within past 2 years	0.749	0.001	0.316 (0.185, 0.447)
L5	0.750	0.001	−0.200 (−0.304, −0.097)

Note: L5 = average log acceleration during the least active 5 h of the day; RA = relative amplitude; TA = total acceleration. Variables are listed in order of their inclusion into the model and the 10-fold cross-validated Concordance from a model which includes all variables up to the current variable is presented in the second column. The third column presents the improvement in cross-validated Concordance from including the current variable in the model. The fourth column presents the estimated coefficient and 95% confidence intervals obtained from the final model fit. Coefficients for total acceleration, relative amplitude, and L5 have been standardized such that interpretation is in units of SDs. Sedentary time is expressed in units of minutes.