[Sleep disorders associated with essential tremor and Parkinson's disease]

To evaluate the sleep quality and explore the manifestations of sleep disorders for 62 essential tremor (ET) patients, 60 normal controls and 62 Parkinson's disease (PD) patients.

A total of 62 ET patients, 60 normal controls and 62 PD patients from June 2009 to December 2013 were recruited. All of them were outpatients at Second Affiliated Hospital, Soochow University and Hospital of Changshu Hospital of Traditional Chinese Medicine. Sleep was assessed with Pittsburgh Sleep Quality Index (PSQI) and Epworth Sleepiness Scale (ESS).

The global PSQI score was 4.7 ± 2.5 in controls, 6.0 ± 4.0 in ET cases and 7.4 ± 3. 7 in PD cases. PD cases had the highest PSQI score, followed by ET (intermediate) and lowest scores in controls (F = 9.022, P = 0.000). A poor quality of sleep was observed in normal controls (23/62, 38.3%) compared to ET cases (34/62, 54.8%) and PD cases (40/62, 64.5%) (χ² = 8.555, P = 0.014 when comparing all three groups and χ² = 1.206, P = 0.272 when ET vs PD). The ESS score increased from normal controls (4.4 ± 2.5) to ET cases (6.3 ± 4.8) and PD cases (8.2 ± 4.2). An ESS score ≥ 10 (an indicator of greater than normal levels of daytime sleepiness) was observed in 6 (10.0%) normal controls, compared to ET cases (16, 25.8%) and PD cases (20, 32.3%) (χ² = 9.047, P = 0.011 when comparing all three groups and χ² = 0.626, P = 0.429 when ET vs PD). For normal controls, ET and PD patients, the factor scores of subjective sleep were 0.6 ± 0.7, 0.8 ± 0.8 and 1.1 ± 0.7; the factor scores of quality sleep latency 0.6 ± 0.7, 0.9 ± 0.9 and 1.1 ± 1.0; the factor scores of sleep duration 0.6 ± 0.8, 0.7 ± 1.0 and 1.0 ± 0.9; the factor scores of sleep efficiency 0.6 ± 0.8, 0.9 ± 0.9 and 1.0 ± 1.0; the factor scores of sleep disturbances 1.2 ± 0.6, 1.2 ± 0.5 and 1.7 ± 0.7; the factor scores of daytime dysfunction 1.2 ± 1.0, 1.3 ± 1.0 and 2.0 ± 1.1 respectively. There were inter-group statistical differences in subjective sleep (F = 7.709, P = 0.001), quality sleep latency (F = 4.414, P = 0.013), sleep duration (F = 4.464, P = 0.013), sleep efficiency (F = 3.201, P = 0.043), sleep disturbances (F = 12.594, P = 0.000) and daytime dysfunction (F = 9.022, P = 0.000) . However, no inter-group statistical differences existed in use of sleeping medication (F = 1.200, P = 0.304). There were statistical differences in subjective sleep (P < 0.05), sleep efficiency (P < 0.05) and daytime dysfunction (P < 0.05) between ET and PD patients.

Some sleep scores in ET are intermediate between those of PD cases and normal controls. And it suggests that a mild form of sleep dysregulation may be present in ET.