Objective vs Subjective Measures of Sleep Quality in PD Differ When Using Sleep Studies

Subjective associations of poor sleep are known to be linked with worse health-related quality of life in Parkinson disease, but correlating objective measures are harder to find.

Researchers sought to show a link between health-related quality of life (HRQOL) and sleep quality in patients with Parkinson disease (PD) using objective measurements obtained from sleep studies, but the results did not align with expectations.

The researchers did the study because the relationship between HRQOL and measures of sleep obtained using polysomnography (PSG) is unclear.

Sleep disorders in PD belong to a large group of nonmotor symptoms, including depression, cognitive dysfunction, and autonomic disturbances; these nonmotor symptoms may appear years before an official diagnosis. Sleep disorders in PD may include comorbid rapid eye movement (REM) sleep behavior disorder (RBD), restless legs syndrome, and sleep disordered breathing.

The authors said previous research has not specifically examined the link between HRQOL and sleep parameters obtained from a PSG. Their hypothesis was that PSG-measured severity indices of sleep disorders would be linked with the physical HRQOL in PD.

The study was carried out in Japan, looking at data from January 2012 to December 2018. The retrospective analysis collected data from 120 patients who were admitted to a hospital for medication adjustments, rehabilitation, and for the assessment of activities of daily living, with 118 patients (46 females and 72 male) included in the final analysis.

Patients were stratified by PD severity, with Hoehn and Yahr stage (H&Y) of 0–2 and 2.5–5 defined as “mild” and “moderate-to-severe” PD, respectively; there were 69 mild cases and 49 moderate-to-severe cases. The mean H&Y stage was 2.25 (0.78) and the mean (SD) age was 67.06 (8.77) years.

Upon admission, patients answered several questionnaires, including:

  • The Epworth Sleepiness Scale (ESS) to assess daytime sleepiness
  • The Pittsburgh Sleep Quality Index (PSQI) to assess sleep quality and disturbances over a 1-month period; the PSQI consists of 18 items, with 7 components: overall sleep quality, sleep-onset latency, sleep duration, sleep efficiency, sleep disturbances, use of sleep medication, and daytime dysfunction due to sleepiness
  • The RBD screening questionnaire (RBDSQ) to evaluate the severity of RBD
  • The Medical Outcomes Study 36-Item Short-Form Health Survey (SF-36) to assess HRQOL

The PSG was completed within 2 weeks of admission, except for 1 case.

The authors said this is the first study to probe the relationship between HRQOL and objective sleep measures using PSG in patients with PD, and that the results indicate there is little association between objective sleep measures and decreased physical or mental HRQOL.

Contrary to their hypothesis, none of the severity scores for comorbid sleep disorders were associated with physical HRQOL in PD patients.

Neither type of HRQOL studied linked to objective sleep measures, including indicators of sleep architecture, sleep-disordered breathing, and sleep-related movement disorders.

There was no correlation between physical HRQOL with higher apnea hypopnea index or oxygen desaturation scores in patients with moderate-to-severe PD, and an unclear association of obstructive sleep apnea in PD HRQOL. There was also no correlation between the periodic limb movement index and poor HRQOL.

However, multiple regression analysis showed that the total PSQI score (a higher PSQI score means worse subjective sleep quality) was linked with both physical and mental HRQOL (P <.001 in both cases). A higher PSQI score was correlated in PSG results with shorter sleep latency, less N1 sleep, and more N2 sleep (N1 is the period between wake and sleep, and N2 occurs throughout sleep).

The researchers called their findings preliminary and said future studies need larger sample sizes to examine the association of HRQOL and sleep measures in these patients. The study was also limited by its retrospective, single-center design. In addition, the severity of PD was evaluated only during the patients’ "on" phase and that the use of the Movement Disorder Society-Unified Parkinson's Disease Rating Scale might have preferable.

Reference

Tsuru A, Matsui K, Kimura A, et al. Sleep disturbance and health-related quality of life in Parkinson's disease: a clear correlation between health-related quality of life and subjective sleep quality. Parkinsonism Relat Disord. Published online April 30, 2022. doi:/10.1016/j.parkreldis.2022.04.014