Reduced rapid eye movement (REM) and other abnormalities during sleep were associated with a greater risk of Parkinson disease (PD) development in older adults, according to study findings published in Sleep.
Characterized by motor flunctuations, PD is also commonly associated with nonmotor symptoms such as sleep-wake disturbances. Study author Abidemi I. Otaiku, BMBS, BSc, AKC, Department of Neurology, Birmingham City Hospital, noted that 40% to 90% of patients experience at least 1 sleep condition, in which certain disorders, including REM sleep behaviour disorder (RBD), can predate the onset of PD by years or even decades.
Despite known alterations in the sleep macro- and microstructure of people with PD, as measured via polysomnography (PSG) and sleep electroencephalogram (qEEG), respectively, he said that it remains unknown whether these factors may also precede the development of PD.
“Establishing the temporal relationship between objective sleep alterations and the development of PD may have important value for early diagnosis, better understanding the pathophysiology of PD, and might open up new approaches for delaying or preventing PD onset,” noted Otaiku.
He derived data from the Outcomes of Sleep Disorders in Older Men Sleep Study (MrOS Sleep Study), an observational, longitudinal cohort study of community-dwelling men 65 years or older at 6 clinical centers in the United States, to examine whether macro- and microstructural sleep alterations precede PD development.
A total of 2770 men from the study cohort, who did not have a PD diagnosis and underwent overnight PSG, were included in this longitudinal analysis. A myriad of sleep macro- and microstructure characteristics were evaluated:
- Sleep macrostructure characteristics examined via PSG: total sleep time (TST), percentage of TST spent in stage 1, stage 2, slow-wave sleep (stages 3 and 4 combined) and REM sleep; awakening index (number of transitions from any sleep stage to wakefulness/hour), apnoea-hypopnea index (AHI; accompanied by a 3% or greater oxygen desaturation), minimum oxygen saturations (min SpO2), and periodic limb movement index
- Sleep microstructure characteristics examined via qEEG: mean relative power for frequency bands, including: δ (0.1-4 Hz), θ (4-8 Hz), α (8-12 Hz), and β (12-30 Hz) and γ (> 30 Hz); in addition, using the absolute spectral power for α and θ, the α/θ power ratio (α/θ), a synoptic index of EEG background slowing down, was calculated
Multivariable logistic regression was used to estimate risk for incident PD by quartiles of PSG measures, with adjustment for sociodemographic characteristics, medical comorbidities, and lifestyle factors. Of the study cohort, 70 (2.5%) cases of incident PD were identified over a median follow-up time of 9.8 years.
After adjusting for potential confounding factors, longer TST (odds ratio [OR], 2.2; 95% CI, 1.0-4.5; P = .046), lower REM percentage (OR, 2.58; 95% CI, 1.3-5.2; P < .008), a lower α/θ ratio during non-REM sleep (OR, 3.71; 95% CI, 1.8-7.7; P < .001), and higher minimum SpO2 during REM sleep (OR, 3.25; 95% CI, 1.5-7.2; P = .004) were each associated with an increased risk of developing PD.
Conversely, a higher awakening index (OR, 0.35; 95% CI, 0.2-0.7; P = .006) and higher AHI (OR, 0.41; 95% CI, 0.2-0.9; P = .019) were associated with decreased risk of developing PD. All associations remained significant when cases occurring within the first 2 years of follow-up were excluded from the analyses.
“These novel findings demonstrate that objective sleep alterations precede the development of PD by several years, and that a single-night, unattended, in-home PSG assessment, may be a useful way by which to identify individuals in the general population at high-risk of developing PD,” concluded Otaiku.
He added that future studies are warranted to establish whether these abnormalities are markers of preclinical PD or causal risk factors. Limitations of the study included the possibility of reverse causality and the lack of generalizability to women and younger adults.
Otaiku AI. Association of sleep abnormalities in older adults with risk of developing Parkinson’s disease. Sleep. Published online August 29, 2022. doi:10.1093/sleep/zsac206