The following is a summary of the “Sleep spindles in people with schizophrenia, schizoaffective disorders or bipolar disorders: a pilot study in a general population-based cohort” published in the December 2022 issue of Psychiatry by Petit et al.

Loss of sleep spindles has been linked to schizophrenia and may serve as a biomarker for the disorder due to its role in sleep stabilization and sleep-related memory systems. However, it is unclear whether this sleep pattern is unique to schizophrenia or whether other illnesses share it with psychotic symptoms. Addressing this gap, researchers evaluated sleep spindles in a prospective population-based cohort who underwent psychiatric assessment (CoLaus|PsyCoLaus) and polysomnographic recording (HypnoLaus). A total of 1,037 people participated in the PsyCoLaus study, and their nightly sleep patterns were monitored using ambulatory polysomnography. In addition, people with a history of schizophrenia (SZ), schizoaffective depression (SAD), schizoaffective mania (SAM), bipolar disorder type I (BP-I), and bipolar disorder type II (BP-II) had their sleep spindle parameters assessed (BP-II). 

The density, duration, frequency, and maximum amplitude of all spindles, slow spindles, and fast spindles were analyzed, as were the correlations between lifetime diagnostic status (independent variables) and spindle parameters (dependent variables). Using a contrast testing framework from our multiple linear mixed models, investigators compared the SZ group to each of the other psychiatric groups with regard to the various spindle parameters. They found that persons with SZ have much less dense and shorter sleep spindles. They also showed that people who had been diagnosed with SAD, SAM, BP-I, or BP-II had distinctive sleep spindle morphologies. In addition, people with a history of manic symptoms (SAM, BP-I, and BP-II) had different spindle densities and frequencies compared to individuals without a history of manic symptoms (SZ, SAD).

This pilot study added additional evidence suggesting a deficit of sleep spindle density and duration in patients with schizophrenia, despite having been conducted on a very limited number of participants due to the low prevalence of these diseases in the general community. In addition, their findings suggest that the frequency of sleep spindles may be more impacted by diagnoses that include a history of mania or hypomania, although they may expect a gradual shift in the intensity of the same sleep spindle parameters through psychotic illnesses. To confirm these results, more research is needed with a bigger sample size.