Presently, NIV is initiated in ALS when FVC falls below 50% or the patient is dyspneic. Additionally, sleep disorders have been described in ALS and some investigators utilize sleep studies to titrate NIV. The Pittsburgh Sleep Quality Questionnaire Index (PSQI) and the Epworth Sleepiness Scale (ESS) are validated questionnaires used to detect sleep disorders. We evaluated the correlation of the PSQI and the ESS with pulmonary function in ALS. 

153 patients were enrolled as part of a multicenter pilot study of nutrition and NIPPV in ALS. All participants completed the ESS and PSQI at their baseline visit along with the ALSFRS-R score, ALS Functional Dyspnea Scale (ALSFDS), Supine FVC (sFVC) and upright FVC (uFVC). The relationship between these measurements and the questionnaires was evaluated using Pearson Correlation Coefficients. 

The mean baseline scores for the scales were: ALSFRS-R 31.2 +/- 9.06, PSQI 7.95 +/- 3.99, and ESS 5.38 +/- 3.78. The number of questionnaires collected were: 87 for ALSFRS-R, 73 for ALSFDS, PSQI and ESS. The ALSFRS-R showed the best correlation with the uFVC (R = 0.76, p<0.001) and sFVC (R= 0.61, p<0.001). The PSQI correlation with uFVC (R = -0.22, p = 0.06) and sFVC (R = -0.14, p = 0.26) was not significant. The ESS correlation with uFVC (R = -0.19, p = 0.11) and sFVC (R = -0.18, p = 0.14) was not significant.

The ALSFRS-R scale was most significantly correlated to supine & upright FVC when compared with PSQI and ESS. This suggests that sleep symptoms detected by questionnaires are not as sensitive to declining in respiratory function as changes on ALSFRS-R.