Table 3.
Independent Associations Between Reported Agitation Scores on the Cohen-Mansfield Agitation Inventory and Lighting Treatment, Resident Characteristics, and Selected Environmental Factors: Results of a Linear Mixed Model (N=66 residents, 1,010 observations)*
| Variable | North Carolina | Oregon | ||||
|---|---|---|---|---|---|---|
| Estimate | (95% CI) | p-value | Estimate | (95% CI) | p-value | |
| Intercept | 24.47 | (17.77, 31.16) | <0.001 | 12.82 | (3.49, 22.15) | 4.762 |
| Treatment Pair Comparison† | 0.011‡ | 0.157‡ | ||||
| AM light vs. Standard | 0.89 | (−0.64, 2.41) | 0.255 | −0.91 | (−2.29, 0.47) | 0.196 |
| PM light vs. Standard | 0.56 | (−1.06, 2.18) | 0.497 | −0.05 | (−1.49, 1.40) | 0.952 |
| All Day vs. Standard | −1.53 | (−3.14, 0.08) | 0.064 | 0.72 | (−0.78, 2.21) | 0.349 |
| AM light vs. PM light | 0.32 | (−1.24, 1.88) | 0.685 | −0.87 | (−2.44, 0.71) | 0.283 |
| AM light vs. All Day light | 2.41 | (0.93, 3.89) | 0.002 | −1.63 | (−3.09, –0.16) | 0.030 |
| PM light vs. All Day light | 2.09 | (0.44, 3.73) | 0.013 | −0.76 | (−2.05, 0.53) | 0.248 |
| Female gender | 3.61 | (−0.59, 7.81) | 0.093 | 3.85 | (−3.56, 11.25) | 0.309 |
| Mild/moderate dementia | −3.42 | (−7.26, 0.43) | 0.083 | −2.67 | (−6.13, 0.79) | 0.131 |
| Staff shift (Ref: night shift) | 0.040∥ | 0.883∥ | ||||
| Day shift | 0.14 | (−2.96, 3.23) | 0.930 | −0.42 | (−2.91, 2.08) | 0.742 |
| Evening shift | 3.63 | (0.24, 7.01) | 0.036 | 0.34 | (−3.22, 3.90) | 0.852 |
| Day length (hrs) | −0.22 | (−0.67, 0.24) | 0.348 | 0.22 | (−0.30, 0.73) | 0.407 |
| Rate of change of day length (min/day) | 0.53 | (0.14, 0.92) | 0.008 | 0.28 | (−0.15, 0.71) | 0.202 |
| Sedative medication score | −0.05 | (−0.11, 0.01) | 0.080 | 0.37 | (0.02, 0.71) | 0.037 |
| Analgesic medication score | 0.12 | (−0.12, 0.35) | 0.326 | 0.12 | (−0.27, 0.52) | 0.539 |
Because a significant (p<0.001) site-by-treatment interaction effect was present, mixed models were estimated separately for the North Carolina and Oregon study sites. Each analysis included resident and staff random effects and all fixed effects shown; thus, all values are adjusted for other variables shown. The estimate (SE) for the resident variance is 27.71 (6.98), p<0.001 for NC and 12.30 (4.55), p=0.003 for OR; for the staff variance it is 17.14 (6.31), p=0.003 for NC and 6.75 (4.09), p=0.049 for OR; residual variance is 33.25 (2.14), p<0.001 for NC and 15.72 (1.11), p<0.001 for OR.
AM light = 7AM – 11AM high intensity light; PM light = 4 PM – 8 PM high intensity light; All Day light = 7 AM – 8 PM high intensity light; Standard = recommended minimum Standard lighting for task areas for older persons (500–600 lux)
P-value for overall F test (3 df) for lighting treatment (for NC and OR respectively)
P-value for overall F test (2 df) for staff shift; the p-value for day vs. evening shift is 0.021 for NC and 0.653 for OR.