Table 2.

Correlation of baseline and longitudinal changes in spirometry and respiratory muscle strength.

Variable	Respiratory muscle strengthbl	Change in spirometry	Change in respiratory muscle strength
Spirometrybl	0.63*	−0.26*	−0.130
Respiratory	–	0.05	−0.25*
Muscle strengthbl
Change in spirometry		–	0.57*

Estimated correlation (*p < 0.002) between of the baseline and longitudinal terms included in the simultaneous bivariate random coefficient models (Figure 2). The core model included terms for baseline spirometry and respiratory muscle function and their interaction with Time i.e., the rate of change in spirometry and the rate of change in and respiratory muscle function.