Primary hypothyroidism and chronotypes in adult women.

OBJECTIVE: Abnormal thyroid function may disrupt sleep architecture. We aimed to determine the frequency of various chronotypes in women with hypothyroidism. We performed a single-center retrospective study at an ambulatory clinic from January 2013-December 2015. Participants were women with hypothyroidism. Chronotype was determined from the Munich ChronoType Questionnaire. The χ2 test was used to compare differences in clinical characteristics and sleep patterns in early and intermediate/late chronotypes. The t test was used to compare differences between means. RESULTS: We evaluated 99 patients (mean [SD], 56 [7] years): calculated chronotype revealed: 56% early, 38% intermediate and 6% late. Analysis with the χ2 test showed significant differences between early and intermediate/late calculated chronotypes for sleep latency (P = 0.01), light exposure (P = 0.009), and no alcohol intake (P = 0.001). t test showed the following differences in mean (SD) between chronotypes: sleep duration, 7.30 (1.39) hours (early chronotype) and 7.04 (2.06) hours (intermediate/late); body mass index (BMI), 29.4 (7.3) (early) and 31.1 (6.8) (intermediate/late); and TSH level, 2.89 (3.69) mIU/L (early) and 1.69 (1.41) mIU/L (intermediate/late). Early chronotypes were frequent in women with hypothyroidism. Light exposure and BMI may influence chronotypes in patients with hypothyroidism; findings are consistent with healthier behaviors in patients who tend toward morningness.

A comparison of 2 visual methods for classifying obstructive vs central hypopneas.

STUDY OBJECTIVES: Rules for classifying apneas as obstructive, central, or mixed are well established. Although hypopneas are given equal weight when calculating the apnea-hypopnea index, classification is not standardized. Visual methods for classifying hypopneas have been proposed by the American Academy of Sleep Medicine and by Randerath et al (Sleep. 2013;36[3]:363-368) but never compared. We evaluated the clinical suitability of the 2 visual methods for classifying hypopneas as central or obstructive. METHODS: Fifty hypopnea-containing polysomnographic segments were selected from patients with clear obstructive or clear central physiology to serve as standard obstructive or central hypopneas. These 100 hypopnea-containing polysomnographic segments were deidentified, randomized, and scored by 2 groups. We assigned 1 group to use the American Academy of Sleep Medicine criteria and the other the Randerath algorithm. After a washout period, re-randomized hypopnea-containing polysomnographic segments were scored using the alternative method. We determined the accuracy (agreement with standard), interrater (Fleiss's κ), and intrarater agreement (Cohen's κ) for obtained scores. RESULTS: Accuracy of the 2 methods was similar: 67% vs 69.3% for Randerath et al and the American Academy of Sleep Medicine, respectively. Cohen's κ was 0.01-0.75, showing that some raters scored similarly using the 2 methods, while others scored them markedly differently. Fleiss's κ for the American Academy of Sleep Medicine algorithm was 0.32 (95% confidence interval, 0.29-0.36) and for the Randerath algorithm was 0.27 (95% confidence interval, 0.23-0.30). CONCLUSIONS: More work is needed to discover a noninvasive way to accurately characterize hypopneas. Studies like ours may lay the foundation for discovering the full spectrum of physiologic consequences of obstructive sleep apnea and central sleep apnea.