A pragmatic behavior-based habit index for adherence to nebulized treatments among adults with cystic fibrosis

Figures & data

Figure 1 An example to illustrate the calculation of SD as a measure of variability for the time of nebulizer use.

Figure 2 An example to illustrate the calculation of SD for time of use in someone using nebulizer over two sessions.

Notes: ^aEvening times were transformed into morning times for accuracy of calculation, otherwise nebulizer taken after midnight may cause spuriously large SD depending on the software used. For example, in someone who uses nebuliser at 23:45, 23:55, 00:15 and 23:52, the difference between 00:15 and 23:55 could be miscalculated as 23 hours and 40 minutes (instead of 20 minutes) if the date was not taken into account. ^bAlthough this treatment was taken after midnight, it is still part of the evening session treatment for 11/01/2013.
Abbreviation: NA, not available.

Figure 3 Illustrative habit index (generated from time of nebulizer use) and adherence time series graphs.

Table 1 The cross-correlation coefficients (R) for the habit index and subsequent adherence

Adherence type	Habit index cross-correlation coefficient, mean (95% CI)
Overall cohort (n=123)	0.40 (0.36–0.44)
Adherence consistently low, ie, ≤25% (n=6)	0.24 (0.04–0.44)
Variable adherence (n=99)	0.45 (0.41–0.49)
Adherence consistently high, ie, >75% (n=18)	0.20 (0.13–0.27)

Table 2 The unstandardized regression coefficients (B)a for the habit index, using time-ordered habit index and current adherence as the covariates with subsequent adherence as the dependent variable in a multiple regression

	Habit index unstandardized coefficient, mean (95% CI)
Overall (n=123)	0.30 (−1.04 to 1.65)
Adherence consistently low, ie, ≤25% (n=6)	3.03 (−9.68 to 15.76)
Variable adherence (n=99)	0.08 (−1.44 to 1.60)
Adherence consistently high, ie, >75% (n=18)	0.61 (−1.90 to 3.13)

Note:

a A regression coefficient of 0.30 meant that 1 unit increase in the habit index (which can vary from 1 [ie, weakest habit] to 7 [ie, strongest habit]) was associated with a 0.3% increase in the subsequent week’s adherence (which can vary from 0 to >100%).