Obstructive sleep apnea (OSA) has been associated with hypertension. It is possible that the association between OSA and hypertension is distinct for non-REM versus REM sleep because of differences in sleep-state-dependent sympathetic activation and/or degree of hypoxemia. We intended to examine the association between REM-related/non-REM-related OSA and hypertension, and whether the severity of OSA modifies such association. A total of 10,102 patients with apnea-hypopnea index (AHI) ≥ 5/h were recruited into this study (83.8% males, mean age = 44.92 ± 11.86 years). Hypertension was defined based either on direct blood pressure measures or on physician diagnosis. OSA severity during REM and non-REM sleep was quantified using the apnea-hypopneaindex in REM (AHIREM) and non-REM sleep (AHINREM), respectively. Linear regression was used to assess the associations of AHIREM and AHINREM with hypertension and blood pressure. A 53.4% was found to have hypertension in total observed OSA patients. After adjusting for age, gender, body mass index (BMI), Epworth sleepiness scale, tobacco use, alcohol use, nocturnal oxygen desaturation, sleep duration and efficiency, AHIREM was only associated with diastolic blood pressure (DBP), while AHINREM was associated with percentage of hypertension, systolic blood pressure (SBP) and DBP. Among mild-moderate OSA patients, AHIREM was associated with DBP (B = 0.87; 95% CI, 0.05-1.58; P = 0.037) while AHINREM was not; among severe OSA patients, AHINREM was associated with percentage of hypertension (B = 0.28; 95% CI, 0.18-0.37; P < 0.001), SBP (B = 7.49; 95% CI, 4.53-10.44; P < 0.001) and DBP (B = 7.23; 95% CI, 5.07-9.38; P < 0.001) , whereas AHIREM was not. The association between AHIREM/AHINREM and hypertension varies across the severity of OSA. Significant association to AHIREM was found in mild-moderate patients, whereas association to AHINREM was only shown in severe patients. This work was supported by the National Natural Science Foundation of China (81530002, 81629002, 81770087) .

Approximately 24–27.6% patients with obstructive sleep apnea (OSA) may have periodic limb movements during sleep (PLMS). The association between OSA and cardiovascular has been well-established. However, the impact of PLMS alone even OSA+PLMS on the cardiovascular system of patients with OSA remains unknown. Heart rate variability (HRV) has been thought as an index reflecting autonomic system activity and may predict cardiovascular illness. The LF spectrum is mediated by both the sympathetic and parasympathetic systems, HF represents only parasympathetic activity. The current study compared HRV during N2 sleep stage in three patient groups and normal control. Eighty adult subjects were retrospectively identified and categorized into control group (n=20, AHI<5/h and PLMI≤15/h), PLMS alone group (n=20, AHI<5/h and PLMI>15/h), OSA alone group (n=20, AHI≥5/h and PLMI≤15/h), and OSA+PLMS group (n=20, AHI≥5/h and PLMI>15/h). All four groups were matched for age, sex and BMI. OSA+PLMS group and OSA alone group were also matched for AHI, OSA+PLMS group and PLMS alone group were also matched for PLMI. Time- and frequency-domain HRV measures were calculated during stable N2 sleep over 5-min periods. The rankings in low frequency power (LF%) and normalized LF power (LFnu) are OSA+PLMS group>control group = PLMS = OSA, by comparison, for high frequency power (HF%) and normalized HF power (HFnu) the significant rankings are OSA+PLMS groupcontrol (0.43 ± 0.18) = PLMS (0.5 ± 0.26) = OSA (0.52 ± 0.21). Only in OSA+PLMS group, HFnu during N2 sleep showed significant negatively relationship with wakefulness time after sleep onset (r=-0.530, p=0.016), other three groups did not have such relationship. The OSA and PLMS patient exhibited an increased sympathetic activity and decreased parasympathetic activity, implying a possible additive effect of OSA and PLMS on HRV. This work was supported by the National Natural Science Foundation of China (81530002, 81770087) and the National Basic Research Program of China (2015CB856406).

Majority of obstructive sleep apnea (OSA) patients exhibit OSA events associated interrupt sleep (e.g., decreased slow wave sleep (SWS) and rapid eye movement (REM) sleep, increased N1 and N2 sleep). There are variations in the activity of autonomic nervous systems across different sleep stages, which may lead to the fluctuation of blood pressure (BP). In particular, an increased vagal tone and reduced sympathetic tone could result in lower BP during SWS. We intended to examine whether different amounts of sleep stages, especially SWS, modifies the relationship between OSA and prevalent hypertension in a large number of OSA patients, and in separate male and female patients. A total of 7107 patients with apnea-hypopnea index (AHI) ≥ 5/h were recruited into this study (84.7% males, mean age = 45.34 ± 11.78 years). Hypertension was defined based either on direct blood pressure measures or on physician diagnosis. Multivariable logistic regression models were adjusted for age, gender, body mass index (BMI), Epworth sleep scale, tobacco use, alcohol use, AHI, nocturnal oxygen desaturation, arousal index, sleep duration and efficiency. A 53.8% was found to have hypertension in total observed OSA patients. In the multi-adjusted model and based on SWS percentage, OSA in quartiles 1 (<0.4%; OR 1.45, 95% CI 1.13–1.70, p=0.001) and 2 (0.4–5.8%; OR 1.21, 95% CI 1.04–1.61, p=0.03), but not quartile 3, had significantly greater odds of prevalent hypertension compared to that in quartile 4 (>12.3%). A significant effect modification by gender on the SWS-hypertension association was found (p=0.004), such association was only existed in male, not in female. No any significant relationship between hypertension and other three sleep stages (N1, N2 and REM %) were obtained in total patients and in separated male and female groups. Decreased SWS, not changes in N1, N2 and REM sleep, is associated with increased odds of prevalent hypertension in male OSA patients. This work was supported by the National Natural Science Foundation of China (81530002, 81770087).

There are strong relationships among daytime sleepiness, obesity and obstructive sleep apnea (OSA) severity. Among OSA patients, some studies suggested that there are strong relationships between obesity and daytime sleepiness, not between OSA severity and daytime sleepiness; though few studies supported the latter relationship. In all those studies, daytime sleepiness was evaluated by Epworth Sleepiness Scale (ESS) alone, not by multiple sleep latency test (MSLT). We explored those relationships utilizing ESS and MSLT simultaneously in OSA patients. A total of 1587 patients with apnea-hypopnea index (AHI) ≥ 5/h were included in this study (85.7% males, mean age = 44.46 ± 11.18 years). All patients underwent ESS and an overnight polysomnography (PSG) followed by MSLT. The ESS and MSLT values were classified into 2 categories based on the cutoff points of 10 score and 5 minutes, respectively. Obesity OSA patients (BMI≥28kg/m2, n=565) had decreases in N2%, N3% and rapid eye movement (REM) sleep% and increases in AHI, total sleep time (TST) and N1% compared with those in non-obesity OSA patients (n=1022). A logistical regression analysis revealed that obesity was associated with subjective sleepiness (ESS score>10) (OR=1.337; 95%CI=1.054 to 1.695), but not objective sleepiness (MSLT score<5min) (OR=1.073; 95%CI=0.816 to 1.412); AHI was associated with objective sleepiness (OR=1.013; 95%CI=1.006 to 1.021), but not subjective sleepiness (OR=1.001; 95%CI=0.994 to 1.007) after adjustment for sex, age, TST, N3%, microarousal index, tobacco use, alcohol drinking, coffee use, hypertension, diabetes and T90%. A multiple linear regression analysis also revealed that obesity (β=0.094, P=0.001), but not AHI (β=0.023, P=0.555) was associated with ESS score; in contrast, AHI (β=-0.121, P=0.002), but not obesity (β=-0.006, P=0.836) was associated with MSLT score. Obesity is associated subjective daytime sleepiness, while OSA severity is associated with objective daytime sleepiness in OSA patients. The results reflect the complexities of physiological mechanisms underlying the associations among daytime sleepiness, obesity and OSA severity. This work was supported by the National Basic Research Program of China (2015CB856406) and National Natural Science Foundation of China (81530002, 81629002).

Obstructive sleep apnea (OSA) and gender are both associated with the level of hemoglobin (HB). Little is known regarding the relationship between the severity of OSA and gender on the level of HB. We aimed to examine their interaction effects on the level of HB in this work. A total of 859 participants with suspected OSA were included. All participants underwent overnight polysomnography (PSG) followed by examining the levels of hemoglobin and erythropoietin (EPO) in the morning. Of all patients, 626 (72.9%) had OSA (an apnea-hypopnea index (AHI)≥5/h); 306 (35.6%) were women (age 46.7 ± 12.9 years, body mass index (BMI) 25.5 ± 4.0 kg/m2), 523 (64.4%) were men (age 45.0 ± 11.7 years, BMI 26.2 ± 4.1 kg/m2). ANOVA analysis revealed a significant interaction between AHI and gender on HB after adjusting for age, BMI, current smoking, drinking, and percentage of time spent in sleep below 90% oxygen saturation (F=6.87, p<0.01). For men, there were no differences in the level of HB among three groups with different levels of AHI (< 5/h, habitual snoring; 5–30/h, mild-moderate OSA; ≥ 30/h, severe OSA). For women, the level of HB in patients with severe OSA was significantly higher than those with habitual snoring and mild-moderate OSA. A cumulative association with AHI level and HB was only obtained in women (p<0.05 for linear trend), not in men. The results provide a novel evidence of mediated interaction between AHI and gender on the level of HB. The increasing severity of OSA is independently associated with a higher level of HB in women, but not in men. This research was funded by the National Basic Research Program of China (2015CB856406), the National Key Technology Research and Development Program of the Ministry of Science and Technology of China (2015BAI13B01), and the National Natural Science Foundation of China (81530002 & 81629002).

Duration of obstructive and mixed apneas increased with altitude descent was found in one small sample study (n=6) among mild-moderate patients with obstructive sleep apnea (OSA). But, there were no studies exploring whether highland native Tibetans and Chinese Hans present prolonged duration of OSA events at low altitude compare to lowland residents. We retrospectively analyzed overnight polysomnography (PSG) records of 558 patients with OSA. The patients included 235 lowland Chinese Hans living at altitude below 1000 m, 181 highland Chinese Hans and 142 highland native Tibetans living at altitude above 3000 m. PSG examinations were carried out in Chengdu (altitude 500 m) after they arrived within 10 days. There were no significant differences in age, gender and apnea-hypopnea index (AHI) among three groups. No differences were obtained in the index (events/h) of central and mixed types of apnea events among three groups. The means of longest and average duration of obstructive apnea events were highland native Tibetan (80.9 ± 57.3, 26.3 ± 11.0 sec) > highland Chinese Hans (60.9 ± 38.5, 23.9 ± 9.0 sec) > lowland Chinese Hans (47.7 ± 24.2, 21.1 ± 6.0 sec). Percentage of number of patients with longest obstructive apnea events above 3 min reached at 5.6% in highland native Tibetans and 1.7% in highland Chinese Hans, whereas none in lowland Chinese Hans. At low altitude, highland OSA patients had significantly prolonged duration of obstructive apnea events, particularly in the longest duration of apnea events, compared to lowland OSA patients. This may implicate that highland residents, especially for highland native Tibetans, may have aggravated OSA at low altitude in terms of the duration of OSA events. This research was funded by the National Basic Research Program of China (2015CB856406), the National Key Technology Research and Development Program of the Ministry of Science and Technology of China (2015BAI13B01), and the National Natural Science Foundation of China (81530002 & 81629002).

Short sleep duration and obstructive sleep apnea (OSA) are both associated with an increased risk of hypertension. We aimed to explore whether polysomnography-determined sleep duration modifies the relationship between OSA and prevalent hypertension. A total of 7048 patients with apnea-hypopnea index (AHI) ≥ 5/h were recruited into this study (84.7% males, mean age = 45.34 ± 11.78 years). Hypertension was defined based either on direct blood pressure measures or on diagnosis by a physician. Patients with sleep duration ≤ 6 h were considered to be short sleepers. Logistic regression procedures were performed to determine the independent association between sleep duration and hypertension in patients with OSA. A 53.8% was found to have hypertension in total observed OSA patients. Considering patients with sleep duration more than 6 hours as reference (n=6032), the odds ratio (OR) (95% confidence intervals) for having hypertension was 1.54 (1.31–1.81) in short sleepers with OSA (n=1016) after adjustment for age, sex, body mass index, diabetes, current smoking, drinking, Epworth sleep scale, time in bed, sleep architecture, arousal index, AHI, and lowest-SaO2. In stratified analyses, the association of hypertension with short sleep duration was seen among sexes, younger and older ages, and both obese and non-obese patients with OSA. Both OSA and hypertension are age-related illnesses. It is important to note that the average age of patients in our study was approximately 10 years younger compared to most of similar observational studies in Caucasian patients. Through this large cross-sectional study in 7048 consecutive Chinese patients with unique age, we obtained that short sleep duration is associated with an increased prevalence of hypertension in patients with OSA. This research was funded by the National Basic Research Program of China (2015CB856406), the National Key Technology Research and Development Program of the Ministry of Science and Technology of China (2015BAI13B01), and the National Natural Science Foundation of China (81530002 & 81629002).