Admixture mapping identifies novel loci for obstructive sleep apnea in Hispanic/Latino Americans

Obstructive sleep apnea (OSA) is a common disorder associated with increased risk of cardiovascular disease and mortality. Its prevalence and severity vary across ancestral background. Although OSA traits are heritable, few genetic associations have been identified. To identify genetic regions associated with OSA and improve statistical power, we applied admixture mapping on three primary OSA traits [the apnea hypopnea index (AHI), overnight average oxyhemoglobin saturation (SaO2) and percentage time SaO2 < 90%] and a secondary trait (respiratory event duration) in a Hispanic/Latino American population study of 11 575 individuals with significant variation in ancestral background. Linear mixed models were performed using previously inferred African, European and Amerindian local genetic ancestry markers. Global African ancestry was associated with a lower AHI, higher SaO2 and shorter event duration. Admixture mapping analysis of the primary OSA traits identified local African ancestry at the chromosomal region 2q37 as genome-wide significantly associated with AHI (P < 5.7 × 10-5), and European and Amerindian ancestries at 18q21 suggestively associated with both AHI and percentage time SaO2 < 90% (P < 10-3). Follow-up joint ancestry-SNP association analyses identified novel variants in ferrochelatase (FECH), significantly associated with AHI and percentage time SaO2 < 90% after adjusting for multiple tests (P < 8 × 10-6). These signals contributed to the admixture mapping associations and were replicated in independent cohorts. In this first admixture mapping study of OSA, novel associations with variants in the iron/heme metabolism pathway suggest a role for iron in influencing respiratory traits underlying OSA.

Associations of variants In the hexokinase 1 and interleukin 18 receptor regions with oxyhemoglobin saturation during sleep

Sleep disordered breathing (SDB)-related overnight hypoxemia is associated with cardiometabolic disease and other comorbidities. Understanding the genetic bases for variations in nocturnal hypoxemia may help understand mechanisms influencing oxygenation and SDB-related mortality. We conducted genome-wide association tests across 10 cohorts and 4 populations to identify genetic variants associated with three correlated measures of overnight oxyhemoglobin saturation: average and minimum oxyhemoglobin saturation during sleep and the percent of sleep with oxyhemoglobin saturation under 90%. The discovery sample consisted of 8,326 individuals. Variants with p < 1 × 10(-6) were analyzed in a replication group of 14,410 individuals. We identified 3 significantly associated regions, including 2 regions in multi-ethnic analyses (2q12, 10q22). SNPs in the 2q12 region associated with minimum SpO2 (rs78136548 p = 2.70 × 10(-10)). SNPs at 10q22 were associated with all three traits including average SpO2 (rs72805692 p = 4.58 × 10(-8)). SNPs in both regions were associated in over 20,000 individuals and are supported by prior associations or functional evidence. Four additional significant regions were detected in secondary sex-stratified and combined discovery and replication analyses, including a region overlapping Reelin, a known marker of respiratory complex neurons.These are the first genome-wide significant findings reported for oxyhemoglobin saturation during sleep, a phenotype of high clinical interest. Our replicated associations with HK1 and IL18R1 suggest that variants in inflammatory pathways, such as the biologically-plausible NLRP3 inflammasome, may contribute to nocturnal hypoxemia.

Sleep Timing, Stability, and BP in the Sueño Ancillary Study of the Hispanic Community Health Study/Study of Latinos

BACKGROUND

Timing and stability of the sleep-wake cycle are potential modifiable risk factors for cardiometabolic disease. The aim of this study was to evaluate the relationship between objective measures of sleep-wake timing and stability with cardiometabolic disease risk.

METHODS

In this multicenter, cross-sectional, population-based study, actigraphy data were obtained from the 2,156 adults, aged 18 to 64 years, recruited from the Sueño ancillary study of the Hispanic Community Health Study/Study of Latinos (2010-2013). These data were correlated with measures of cardiometabolic disease risk, including systolic and diastolic BPs, homeostatic assessment of insulin resistance, glycosylated hemoglobin, BMI, and hypertension and diabetes status.

RESULTS

Each 10% decrease in interdaily stability was associated with a 3.0% absolute increase in the prevalence of hypertension (95% CI, 0.6-5.3; P < .05), an increase in systolic BP by 0.78 mm Hg (95% CI, 0.12-1.45; P < .05) and an increase in diastolic BP by 0.80 mm Hg (95% CI, 0.28-1.32; P < .05). In addition, delaying the midpoint of sleep by 1 h was associated with an increase in systolic BP by 0.73 mm Hg (95% CI, 0.30-1.16; P < .01) and diastolic BP by 0.53 mm Hg (95% CI, 0.17-0.90; P < .01). These associations were not significant after adjusting for shift work status. No association was found between interdaily stability or sleep timing and diabetes, BMI, or insulin resistance.

CONCLUSIONS

These results suggest that beyond sleep duration, the timing and regularity of sleep-wake schedules are related to hypertension prevalence and BP.

Multiethnic Meta-Analysis Identifies RAI1 as a Possible Obstructive Sleep Apnea-related Quantitative Trait Locus in Men

Obstructive sleep apnea (OSA) is a common heritable disorder displaying marked sexual dimorphism in disease prevalence and progression. Previous genetic association studies have identified a few genetic loci associated with OSA and related quantitative traits, but they have only focused on single ethnic groups, and a large proportion of the heritability remains unexplained. The apnea-hypopnea index (AHI) is a commonly used quantitative measure characterizing OSA severity. Because OSA differs by sex, and the pathophysiology of obstructive events differ in rapid eye movement (REM) and non-REM (NREM) sleep, we hypothesized that additional genetic association signals would be identified by analyzing the NREM/REM-specific AHI and by conducting sex-specific analyses in multiethnic samples. We performed genome-wide association tests for up to 19,733 participants of African, Asian, European, and Hispanic/Latino American ancestry in 7 studies. We identified rs12936587 on chromosome 17 as a possible quantitative trait locus for NREM AHI in men (N = 6,737; P = 1.7 × 10-8) but not in women (P = 0.77). The association with NREM AHI was replicated in a physiological research study (N = 67; P = 0.047). This locus overlapping the RAI1 gene and encompassing genes PEMT1, SREBF1, and RASD1 was previously reported to be associated with coronary artery disease, lipid metabolism, and implicated in Potocki-Lupski syndrome and Smith-Magenis syndrome, which are characterized by abnormal sleep phenotypes. We also identified gene-by-sex interactions in suggestive association regions, suggesting that genetic variants for AHI appear to vary by sex, consistent with the clinical observations of strong sexual dimorphism.

Sleep Patterns and Hypertension Using Actigraphy in the Hispanic Community Health Study/Study of Latinos

BACKGROUND

The aim of this study was to evaluate the association between actigraphy-based measures of sleep and prevalent hypertension in a sample of US Latinos.

METHODS

We analyzed data from 2,148 participants of the Sueño Sleep Ancillary Study of the Hispanic Community Health Study/Study of Latinos (HCHS/SOL), who underwent 1 week of wrist actigraphy to characterize sleep duration, sleep efficiency, sleep fragmentation index, and daytime naps. Insomnia was defined as an Insomnia Severity Index ≥ 15. Hypertension was defined based on self-reported physician diagnosis. Survey linear regression was used to evaluate the association of sleep measures with hypertension prevalence. Sensitivity analyses excluded participants with an apnea-hypopnea index (AHI) ≥ 15 events/h.

RESULTS

The mean age was 46.3 ± 11.6 years, and 65% of the sample consisted of women. The mean sleep duration was 6.7 ± 1.1 hours. Thirty-two percent of the sample had hypertension. After adjusting for age, sex, ethnic background, site, and AHI, each 10% reduction in sleep efficiency was associated with a 7.5% (95% CI, -12.9 to -2.2; P = .0061) greater hypertension prevalence, each 10% increase in sleep fragmentation index was associated with a 5.2% (95% CI, 1.4-8.9; P = .0071) greater hypertension prevalence, and frequent napping was associated with a 11.6% greater hypertension prevalence (95% CI, 5.5-17.7; P = .0002). In contrast, actigraphy-defined sleep duration (P = .20) and insomnia (P = .17) were not associated with hypertension. These findings persisted after excluding participants with an AHI ≥ 15 events/h.

CONCLUSIONS

Independent of sleep-disordered breathing, we observed associations between reduced sleep continuity and daytime napping, but not short sleep duration, and prevalent hypertension.

Association Between Sleep Timing, Obesity, Diabetes: The Hispanic Community Health Study/Study of Latinos (HCHS/SOL) Cohort Study

Study Objectives

Recent studies implicate inadequate sleep duration and quality in metabolic disease. Fewer studies have examined the timing of sleep, which may be important because of its potential impact on circadian rhythms of metabolic function. We examined the association between sleep timing and metabolic risk among Hispanic/Latino adults.

Methods

Cross-sectional data from community-based study of 13429 participants aged 18-74 years. People taking diabetic medications were excluded. Sleep timing was determined from self-reported bedtimes and wake times. Chronotype was defined as the midpoint of sleep on weekends adjusted for sleep duration on weekdays. Other measurements included body mass index (BMI), fasting glucose levels, estimated insulin resistance (HOMA-IR), glucose levels 2 hours post oral glucose ingestion, and hemoglobin A1c. Survey linear regression models tested associations between sleep timing and metabolic measures. Analyses were stratified by diabetes status and age-group when significant interactions were observed.

Results

Among participants with diabetes, fasting glucose levels were positively associated with bedtime (approximately +3%/hour later, p < .01) and midpoint of sleep (approximately +2%/hour later, p < .05). In participants with and without diabetes combined, HOMA-IR was positively associated with midpoint of sleep (+1.5%/hr later, p < .05), and chronotype (+1.2%/hour later, p < .05). Associations differed by age-group. Among those < 36 years, later sleep timing was associated with lower BMI, lower fasting glucose, and lower HbA1c, but the opposite association was observed among older participants.

Conclusions

Later sleep timing was associated with higher estimated insulin resistance across all groups. Some associations between sleep timing and metabolic measures may be age-dependent.

Actigraphic Sleep Patterns of U.S. Hispanics: The Hispanic Community Health Study/Study of Latinos

Study objective

To assess the extent to which objective sleep patterns vary among U.S. Hispanics/Latinos.

Methods

We assessed objective sleep patterns in 2087 participants of the Hispanic Community Health Study/Study of Latinos from 6 Hispanic/Latino subgroups aged 18-64 years who underwent 7 days of wrist actigraphy.

Results

The age- and sex-standardized mean (SE) sleep duration was 6.82 (0.05), 6.72 (0.07), 6.61 (0.07), 6.59 (0.06), 6.57 (0.10), and 6.44 (0.09) hr among individuals of Mexican, Cuban, Dominican, Central American, Puerto Rican, and South American heritage, respectively. Sleep maintenance efficiency ranged from 89.2 (0.2)% in Mexicans to 86.5 (0.4)% in Puerto Ricans, while the sleep fragmentation index ranged from 19.7 (0.3)% in Mexicans to 24.2 (0.7)% in Puerto Ricans. In multivariable models adjusted for age, sex, season, socioeconomic status, lifestyle habits, and comorbidities, these differences persisted.

Conclusions

There are important differences in actigraphically measured sleep across U.S. Hispanic/Latino heritages. Individuals of Mexican heritage have longer and more consolidated sleep, while those of Puerto Rican heritage have shorter and more fragmented sleep. These differences may have clinically important effects on health outcomes.

Genetic Associations with Obstructive Sleep Apnea Traits in Hispanic/Latino Americans

RATIONALE

Obstructive sleep apnea is a common disorder associated with increased risk for cardiovascular disease, diabetes, and premature mortality. Although there is strong clinical and epidemiologic evidence supporting the importance of genetic factors in influencing obstructive sleep apnea, its genetic basis is still largely unknown. Prior genetic studies focused on traits defined using the apnea-hypopnea index, which contains limited information on potentially important genetically determined physiologic factors, such as propensity for hypoxemia and respiratory arousability.

OBJECTIVES

To define novel obstructive sleep apnea genetic risk loci for obstructive sleep apnea, we conducted genome-wide association studies of quantitative traits in Hispanic/Latino Americans from three cohorts.

METHODS

Genome-wide data from as many as 12,558 participants in the Hispanic Community Health Study/Study of Latinos, Multi-Ethnic Study of Atherosclerosis, and Starr County Health Studies population-based cohorts were metaanalyzed for association with the apnea-hypopnea index, average oxygen saturation during sleep, and average respiratory event duration.

MEASUREMENTS AND MAIN RESULTS

Two novel loci were identified at genome-level significance (rs11691765, GPR83, P = 1.90 × 10-8 for the apnea-hypopnea index, and rs35424364; C6ORF183/CCDC162P, P = 4.88 × 10-8 for respiratory event duration) and seven additional loci were identified with suggestive significance (P < 5 × 10-7). Secondary sex-stratified analyses also identified one significant and several suggestive associations. Multiple loci overlapped genes with biologic plausibility.

CONCLUSIONS

These are the first genome-level significant findings reported for obstructive sleep apnea-related physiologic traits in any population. These findings identify novel associations in inflammatory, hypoxia signaling, and sleep pathways.

Pulmonary Disease and Age at Immigration among Hispanics. Results from the Hispanic Community Health Study/Study of Latinos

RATIONALE

Asthma has been reported to be more prevalent among Hispanics of Puerto Rican heritage than among other Hispanics and among Hispanics born in the United States or who immigrated as children than among those who came as adults; however, direct comparisons across Hispanic groups are lacking.

OBJECTIVES

To test whether asthma is more prevalent among Hispanics of Puerto Rican heritage than among other Hispanic groups, whether asthma is associated with age of immigration, and whether chronic obstructive pulmonary disease varies by heritage in a large, population-based cohort of Hispanics in the United States.

METHODS

The Hispanic Community Health Study/Study of Latinos researchers recruited a population-based probability sample of 16,415 Hispanics/Latinos, 18-74 years of age, in New York City, Chicago, Miami, and San Diego. Participants self-reported Puerto Rican, Cuban, Dominican, Mexican, Central American, or South American heritage; birthplace; and, if relevant, age at immigration. A respiratory questionnaire and standardized spirometry were performed with post-bronchodilator measures for those with airflow limitation.

MEASUREMENTS AND MAIN RESULTS

The prevalence of physician-diagnosed asthma among Puerto Ricans (36.5%; 95% confidence interval, 33.6-39.5%) was higher than among other Hispanics (odds ratio, 3.9; 95% confidence interval, 3.3-4.6). Hispanics who were born in the mainland United States or had immigrated as children had a higher asthma prevalence than those who had immigrated as adults (19.6, 19.4, and 14.1%, respectively; P < 0.001). Current asthma, bronchodilator responsiveness, and wheeze followed similar patterns. Chronic obstructive pulmonary disease prevalence was higher among Puerto Ricans (14.1%) and Cubans (9.8%) than among other Hispanics (<6.0%), but it did not vary across Hispanic heritages after adjustment for smoking and prior asthma (P = 0.22), by country of birth, or by age at immigration.

CONCLUSIONS

Asthma was more prevalent among Puerto Ricans, other Hispanics born in the United States, and those who had immigrated as children than among other Hispanics. In contrast, the higher prevalence of chronic obstructive pulmonary disease among Puerto Ricans and Cubans was largely reflective of differential smoking patterns and asthma.

Comparison of Self-Reported Sleep Duration With Actigraphy: Results From the Hispanic Community Health Study/Study of Latinos Sueño Ancillary Study

Most studies of sleep and health outcomes rely on self-reported sleep duration, although correlation with objective measures is poor. In this study, we defined sociodemographic and sleep characteristics associated with misreporting and assessed whether accounting for these factors better explains variation in objective sleep duration among 2,086 participants in the Hispanic Community Health Study/Study of Latinos who completed more than 5 nights of wrist actigraphy and reported habitual bed/wake times from 2010 to 2013. Using linear regression, we examined self-report as a predictor of actigraphy-assessed sleep duration. Mean amount of time spent asleep was 7.85 (standard deviation, 1.12) hours by self-report and 6.74 (standard deviation, 1.02) hours by actigraphy; correlation between them was 0.43. For each additional hour of self-reported sleep, actigraphy time spent asleep increased by 20 minutes (95% confidence interval: 19, 22). Correlations between self-reported and actigraphy-assessed time spent asleep were lower with male sex, younger age, sleep efficiency <85%, and night-to-night variability in sleep duration ≥1.5 hours. Adding sociodemographic and sleep factors to self-reports increased the proportion of variance explained in actigraphy-assessed sleep slightly (18%-32%). In this large validation study including Hispanics/Latinos, we demonstrated a moderate correlation between self-reported and actigraphy-assessed time spent asleep. The performance of self-reports varied by demographic and sleep measures but not by Hispanic subgroup.

Obstructive Sleep Apnea and Cognition in Parkinson's disease

OBJECTIVE

Obstructive sleep apnea (OSA) is very common in Parkinson's disease (PD). OSA is known to affect patients' cognition. The present study assessed whether PD patients with OSA (PD + OSA) score lower on cognitive measures than those without OSA (PD - OSA). In addition, this study evaluated whether treating the OSA with continuous positive airway pressure (CPAP) in PD + OSA patients results in an improved cognitive functioning.

METHODS

Eighty-six patients with PD underwent an overnight polysomnography screen for OSA and were administered the Mini-Mental Status Exam (MMSE) and the Montreal Cognitive Assessment (MoCA). This resulted in 38 patients with PD + OSA who were randomly assigned to receive either therapeutic CPAP for 6 weeks (n = 19) or placebo CPAP for three weeks followed by therapeutic CPAP for three weeks (n = 19). Intervention participants completed a neurocognitive battery at baseline and 3- and 6-week time-points.

RESULTS

Patients with PD + OSA scored significantly lower than PD - OSA on the MMSE and MoCA after controlling for age, education, and PD severity. OSA was a significant predictor of cognition (MMSE p <0.01; MoCA p = 0.028).There were no significant changes between groups in cognition when comparing three weeks of therapeutic CPAP with 3 weeks of placebo CPAP. Comparisons between pre-treatment and 3-week post-therapeutic CPAP for the entire sample also revealed no significant changes on overall neuropsychological (NP) scores.

CONCLUSIONS

Findings suggest that PD patients with OSA show worse cognitive functioning on cognitive screening measures than those without OSA. However, OSA treatment after three or six weeks of CPAP may not result in overall cognitive improvement in patients with PD.

Reproducibility of a Standardized Actigraphy Scoring Algorithm for Sleep in a US Hispanic/Latino Population

STUDY OBJECTIVES

While actigraphy is considered objective, the process of setting rest intervals to calculate sleep variables is subjective. We sought to evaluate the reproducibility of actigraphy-derived measures of sleep using a standardized algorithm for setting rest intervals.

DESIGN

Observational study.

SETTING

Community-based.

PARTICIPANTS

A random sample of 50 adults aged 18-64 years free of severe sleep apnea participating in the Sueño sleep ancillary study to the Hispanic Community Health Study/Study of Latinos.

INTERVENTIONS

N/A.

MEASUREMENTS AND RESULTS

Participants underwent 7 days of continuous wrist actigraphy and completed daily sleep diaries. Studies were scored twice by each of two scorers. Rest intervals were set using a standardized hierarchical approach based on event marker, diary, light, and activity data. Sleep/wake status was then determined for each 30-sec epoch using a validated algorithm, and this was used to generate 11 variables: mean nightly sleep duration, nap duration, 24-h sleep duration, sleep latency, sleep maintenance efficiency, sleep fragmentation index, sleep onset time, sleep offset time, sleep midpoint time, standard deviation of sleep duration, and standard deviation of sleep midpoint. Intra-scorer intraclass correlation coefficients (ICCs) were high, ranging from 0.911 to 0.995 across all 11 variables. Similarly, inter-scorer ICCs were high, also ranging from 0.911 to 0.995, and mean inter-scorer differences were small. Bland-Altman plots did not reveal any systematic disagreement in scoring.

CONCLUSIONS

With use of a standardized algorithm to set rest intervals, scoring of actigraphy for the purpose of generating a wide array of sleep variables is highly reproducible.

Periodontitis and Sleep Disordered Breathing in the Hispanic Community Health Study/Study of Latinos

STUDY OBJECTIVES

To investigate the association between sleep disordered breathing (SDB) and severe chronic periodontitis.

DESIGN

Cross-sectional data analysis from the Hispanic Community Health Study/Study of Latinos.

SETTING

Community-based setting with probability sampling from four urban US communities.

PARTICIPANTS

12,469 adults aged 18-74 y.

INTERVENTIONS

None.

MEASUREMENTS AND RESULTS

Severe chronic periodontitis was defined using the Centers for Disease Control and Prevention/American Academy of Periodontology case classification based on full-mouth periodontal assessments performed by calibrated dentists. SDB was evaluated in standardized home sleep tests, and defined as the number of apnea plus hypopnea events associated with ≥ 3% desaturation, per hour of estimated sleep. SDB was quantified using categories of the apnea-hypopnea index (AHI): 0.0 events (nonapneic); 0.1-4.9 (subclinical); 5.0-14.9 (mild); and ≥ 15 (moderate/severe). Covariates were demographic characteristics and established periodontitis risk factors. C-reactive protein was a potential explanatory variable. Using survey estimation, multivariable binary logistic regression estimated odds ratios (OR) and 95% confidence limits (CL). Following adjustment for confounding, the SDB and periodontitis relationship remained statistically significant, but was attenuated in strength and no longer dose-response. Compared with the nonapneic referent, adjusted odds of severe periodontitis were 40% higher with subclinical SDB (OR = 1.4, 95% CL: 1.0, 1.9), 60% higher with mild SDB (OR = 1.6, 95% CL: 1.1, 2.2) and 50% higher with moderate/severe SDB (OR = 1.5, 95% CL: 1.0, 2.3) demonstrating an independent association between SDB and severe periodontitis.

CONCLUSIONS

This study identifies a novel association between mild sleep disordered breathing and periodontitis that was most pronounced in young adults.

Obstructive sleep apnea and neurocognitive function in a Hispanic/Latino population

OBJECTIVE

We evaluated the association between obstructive sleep apnea (OSA) and neurocognitive function among community-dwelling Hispanic/Latino individuals in the United States.

METHODS

Cross-sectional analysis of the Hispanic Community Health Study/Study of Latinos middle-aged and older adults, aged 45 to 74 years, with neurocognitive test scores at baseline measurements from 2008 to 2011. Neurocognitive scores were measured using the Word Fluency (WF) Test, the Brief-Spanish English Verbal Learning Test (SEVLT), and the Digit Symbol Substitution (DSS) Test. OSA was defined by the apnea-hypopnea index (AHI). Multivariable linear regression models were fit to evaluate relations between OSA and neurocognitive scores.

RESULTS

The analysis consisted of 8,059 participants, mean age of 56 years, 55% women, and 41% with less than high school education. The mean AHI was 9.0 (range 0-142; normal AHI <5/h). There was an association between the AHI and all 4 neurocognitive test scores: Brief-SEVLT-sum (β = -0.022) and -recall (β = -0.010), WF (β = -0.023), and DSS (β = -0.050) at p < 0.01 that was fully attenuated by age. In the fully adjusted regression model, female sex was a moderating factor between the AHI and WF (β = -0.027, p < 0.10), SVELT-sum (β = -0.37), SVELT-recall (β = -0.010), and DSS (β = -0.061) at p < 0.01.

CONCLUSION

OSA was associated with worse neurocognitive function in a representative sample of Hispanic/Latino women in the United States.

Parkinson's disease and REM sleep behavior disorder result in increased non-motor symptoms

OBJECTIVE

Rapid eye movement (REM)-sleep behavior disorder (RBD) is often comorbid with Parkinson's disease (PD). The current study aimed to provide a detailed understanding of the impact of having RBD on multiple non-motor symptoms (NMS) in patients with PD.

METHODS

A total of 86 participants were evaluated for RBD and assessed for multiple NMS of PD. Principal component analysis was utilized to model multiple measures of NMS in PD, and a multivariate analysis of variance was used to assess the relationship between RBD and the multiple NMS measures. Seven NMS measures were assessed: cognition, quality of life, fatigue, sleepiness, overall sleep, mood, and overall NMS of PD.

RESULTS

Among the PD patients, 36 were classified as having RBD (objective polysomnography and subjective findings), 26 as not having RBD (neither objective nor subjective findings), and 24 as probably having RBD (either subjective or objective findings). RBD was a significant predictor of increased NMS in PD while controlling for dopaminergic therapy and age (p=0.01). The RBD group reported more NMS of depression (p=0.012), fatigue (p=0.036), overall sleep (p=0.018), and overall NMS (p=0.002).

CONCLUSION

In PD, RBD is associated with more NMS, particularly increased depressive symptoms, sleep disturbances, and fatigue. More research is needed to assess whether PD patients with RBD represent a subtype of PD with different disease progression and phenomenological presentation.

Continuous positive airway pressure improves sleep and daytime sleepiness in patients with Parkinson disease and sleep apnea

STUDY OBJECTIVES

Obstructive sleep apnea (OSA), common in Parkinson disease (PD), contributes to sleep disturbances and daytime sleepiness. We assessed the effect of continuous positive airway pressure (CPAP) on OSA, sleep, and daytime sleepiness in patients with PD.

DESIGN

This was a randomized placebo-controlled, crossover design. Patients with PD and OSA were randomized into 6 w of therapeutic treatment or 3 w of placebo followed by 3 w of therapeutic treatment. Patients were evaluated by polysomnography (PSG) and multiple sleep latency test (MSLT) pretreatment (baseline), after 3 w, and after 6 w of CPAP treatment. Analyses included mixed models, paired analysis, and within-group analyses comparing 3 w to 6 w of treatment.

SETTING

Sleep laboratory.

PARTICIPANTS

Thirty-eight patients with PD (mean age = 67.2 ± 9.2 y; 12 females).

INTERVENTION

Continuous positive airway pressure.

MEASUREMENTS

PSG OUTCOME MEASURES: sleep efficiency, %sleep stages (N1, N2, N3, R), arousal index, apnea-hypopnea index (AHI), and % time oxygen saturation < 90% (%time SaO2 < 90%). MSLT outcome measures: mean sleep-onset latency (MSL).

RESULTS

There were significant group-by-time interactions for AHI (P < 0.001), % time SaO2 < 90% (P = 0.02), %N2 (P = 0.015) and %N3 (P = 0.014). Subjects receiving therapeutic CPAP showed significant decrease in AHI, %time SaO2 < 90%, %N2, and significant increase in %N3 indicating effectiveness of CPAP in the treatment of OSA, improvement in nighttime oxygenation, and in deepening sleep. The paired sample analyses revealed that 3 w of therapeutic treatment resulted in significant decreases in arousal index (t = 3.4, P = 0.002). All improvements after 3 w were maintained at 6 w. Finally, 3 w of therapeutic CPAP also resulted in overall decreases in daytime sleepiness (P = 0.011).

CONCLUSIONS

Therapeutic continuous positive airway pressure versus placebo was effective in reducing apnea events, improving oxygen saturation, and deepening sleep in patients with Parkinson disease and obstructive sleep apnea. Additionally, arousal index was reduced and effects were maintained at 6 weeks. Finally, 3 weeks of continuous positive airway pressure treatment resulted in reduced daytime sleepiness measured by multiple sleep latency test. These results emphasize the importance of identifying and treating obstructive sleep apnea in patients with Parkinson disease.

Effects of sleep disorders on the non-motor symptoms of Parkinson disease

STUDY OBJECTIVES

To evaluate the impact of sleep disorders on non-motor symptoms in patients with Parkinson disease (PD).

DESIGN

This was a cross-sectional study. Patients with PD were evaluated for obstructive sleep apnea (OSA), restless legs syndrome (RLS), periodic limb movement syndrome (PLMS), and REM sleep behavior disorder (RBD). Cognition was assessed with the Montreal Cognitive Assessment and patients completed self-reported questionnaires assessing non-motor symptoms including depressive symptoms, fatigue, sleep complaints, daytime sleepiness, and quality of life.

SETTING

Sleep laboratory.

PARTICIPANTS

86 patients with PD (mean age = 67.4 ± 8.8 years; range: 47-89; 29 women).

INTERVENTIONS

N/A.

MEASUREMENTS AND RESULTS

Having sleep disorders was a predictor of overall non-motor symptoms in PD (R(2) = 0.33, p < 0.001) while controlling for age, PD severity, and dopaminergic therapy. These analyses revealed that RBD (p = 0.006) and RLS (p = 0.014) were significant predictors of increased non-motor symptoms, but OSA was not. More specifically, having a sleep disorder significantly predicted sleep complaints (ΔR(2) = 0.13, p = 0.006), depressive symptoms (ΔR(2) = 0.01, p = 0.03), fatigue (ΔR(2) = 0.12, p = 0.007), poor quality of life (ΔR(2) = 0.13, p = 0.002), and cognitive decline (ΔR(2) = 0.09, p = 0.036). Additionally, increasing number of sleep disorders (0, 1, or ≥ 2 sleep disorders) was a significant contributor to non-motor symptom impairment (R(2) = 0.28, p < 0.001).

CONCLUSION

In this study of PD patients, presence of comorbid sleep disorders predicted more non-motor symptoms including increased sleep complaints, more depressive symptoms, lower quality of life, poorer cognition, and more fatigue. RBD and RLS were factors of overall increased non-motor symptoms, but OSA was not.

Actigraphy for the assessment of sleep measures in Parkinson's disease

OBJECTIVES

To assess the usefulness of actigraphy for assessment of nighttime sleep measures in patients with Parkinson's disease (PD).

DESIGN

Participants underwent overnight sleep assessment simultaneously by polysomnography (PSG) and actigraphy.

SETTING

Overnight sleep study in academic sleep research laboratory.

PARTICIPANTS

Sixty-one patients (mean age 67.74 ± 8.88 y) with mild to moderate PD.

MEASUREMENTS

Sleep measures including total sleep time (TST), sleep efficiency (SE), wake after sleep onset (WASO), and sleep onset latency (SOL) were calculated independently from data derived from PSG and from actigraphy. Different actigraphy scoring settings were compared.

RESULTS

No single tested actigraphy scoring setting was optimal for all sleep measures. A customized setting of an activity threshold of 10, with five consecutive immobile minutes for sleep onset, yielded the combination of mean TST, SE, and WASO values that best approximated mean values determined by PSG with differences of 6.05 ± 85.67 min for TST, 1.1 ± 0.641% for SE, and 4.35 ± 59.56 min for WASO. There were significant but moderate correlations between actigraphy and PSG measurements (rs = 0.496, P < 0.001 for TST, rs = 0.384, P = 0.002 for SE, and rs = 0.400, P = 0.001 for WASO) using these settings. Greater disease stage was associated with greater differences between TST (R(2) = 0.099, beta = 0.315, P = 0.018), SE (R(2) = 0.107, beta = 0.327, P = 0.014), and WASO (R(2) = 0.094, beta = 0.307, P = 0.021) values derived by actigraphy and PSG explaining some of the variability. Using a setting of 10 immobile min for sleep onset yielded a mean SOL that was within 1 min of that estimated by PSG. However SOL values determined by actigraphy and PSG were not significantly correlated at any tested setting.

CONCLUSIONS

Our results suggest that actigraphy may be useful for measurement of mean TST, SE, and WASO values in groups of patients with mild to moderate Parkinson's disease. However, there is a significant degree of variability in accuracy among individual patients. The importance of determining optimal scoring parameters for each population studied is underscored.

Relationships between clinical characteristics and nocturnal cardiac autonomic activity in Parkinson's disease

BACKGROUND

The aim of the present study was to explore the association between Parkinson's disease (PD) clinical characteristics and cardiac autonomic control across sleep stages.

METHODS

Frequency-domain heart rate variability (HRV) measures were estimated in 18 PD patients undergoing a night of polysomnography.

RESULTS

Significant relationships were found between PD severity and nocturnal HRV indices. The associations were restricted to rapid eye movement (R) sleep.

CONCLUSIONS

The progressive nocturnal cardiac autonomic impairment occurring with more severe PD can be subclinical emerging only during conditions requiring active modulation of physiological functions such as R-sleep.

Clinical correlates of periodic limb movements in sleep in Parkinson's disease

OBJECTIVE

The aim of the current study was to investigate the frequency of periodic limb movements in sleep (PLMS) in Parkinson's disease (PD) and their impact on nocturnal sleep and daytime functioning.

METHODS

Forty-five PD patients (mean age 68.5 ± 8.7 years; 32 males) underwent one night of polysomnography (PSG). Clinical assessment and questionnaires evaluating sleep disturbance and quality of life (QoL) were completed. Patients were divided into two groups based on their PLMS index (PLMSI): PLMSI ≥ 15 (PLMS+) and PLMSI <15 (PLMS-).

RESULTS

There were 26 (57.8%) PD patients in the PLMS+group and 19 (42.2%) patients in the PLMS-group. Subjective assessment revealed an association between PLMS+status and greater PD symptom severity, more subjective sleep disturbance, and decreased QoL. All patients showed poor sleep, and no significant group differences were detected on PSG measures.

CONCLUSION

We observed that PLMS occurred frequently in PD and increased with more severe PD. Although PLMS did not affect objective sleep, it was associated with increased sleep complaints and reduced QoL. Overall, our findings support the association between PLMS and PD as well as the clinical relevance of sleep disturbances in PD.

Characterizing Fatigue: The Effects of Ethnicity and Acculturation

It is unknown if fatigue measures like the Multidimensional Fatigue Symptom Inventory-Short Form (MFSI-SF; Stein, Jacobsen, Blanchard, & Thors, 2004) appropriately describe fatigue in Hispanics or if acculturation plays a role in fatigue. This study compared fatigue in community samples of Hispanics and Anglos. The MFSI-SF and pertinent questionnaires were administered to adults in San Diego County via telephone survey. Some differences in fatigue were observed in initial comparisons between Hispanics and Anglos, including when acculturation was considered. When age and education were controlled, Hispanics reported less general fatigue than Anglos, regardless of acculturation status, p = < .01. Exploratory factor analyses indicate that the MFSI-SF general-fatigue subscale was problematic for Hispanics. Implications, limitations, and future directions are discussed.

A Model for Studying Neuropsychological Effects of Sleep Intervention: The Effect of 3-week Continuous Positive Airway Pressure Treatment

PURPOSE: Patients with obstructive sleep apnea (OSA) commonly have cognitive complaints. There are few randomized studies that have examined neuropsychological effects of continuous positive airway pressure (CPAP) treatment in patients with OSA. In this double-blind trial, we examined if a 3-week CPAP treatment compared with placebo CPAP treatment has specific therapeutic effects on cognitive impairments in patients with OSA and if there are specific domains of cognitive impairments sensitive to 3-week CPAP treatment. SUBJECTS AND METHODS: Thirty-eight newly diagnosed patients with untreated OSA underwent neuropsychological testing before and after 3-weeks CPAP or Placebo CPAP treatment. The two treatment groups (therapeutic CPAP, and placebo-CPAP) were compared using repeated measures analysis of variance (ANOVA). RESULTS AND CONCLUSION: Impairments in neuropsychological functioning ranged from 2.6% to 47.1% before treatment. In response to 3 weeks of treatment, there was no significant time by treatment interaction for a global deficit score of neuropsychological functioning. Only the Stroop Color (number correct) test showed significant improvement specific to CPAP treatment. The study demonstrates the importance of further randomized placebo controlled studies in this area.

The Relationship between psychomotor vigilance performance and quality of life in obstructive sleep apnea

OBJECTIVE

Patients with obstructive sleep apnea (OSA) commonly have cognitive complaints, particularly in attention, and report decreased quality of life. We examined how vigilance and sustained attention, as assessed by the Psychomotor Vigilance Task (PVT), were related to quality of life after controlling for apnea severity and depression in subjects with OSA.

SUBJECTS AND METHODS

Fifty-seven patients with newly diagnosed and untreated OSA had their sleep monitored with polysomnography. Quality of life was assessed by the Short Form-36 health survey questionnaire (SF-36). Mood was assessed by the Center for Epidemiologic Studies-Depression (CES-D) Scale. After sleep monitoring and psychological assessments were performed, the 10-minute PVT was administered. The main outcome variables were PVT lapse count and average response time (RT). Simple correlations and multiple linear regression were used to examine the association between PVT performance and age, body mass index, sleep variables, apnea hypopnea index, oxygen desaturation index, and CES-D.

RESULTS AND CONCLUSION

Both the PVT lapse count and RT were significantly associated with the SF-36 physical component summary score (PCS). In multiple linear regression, PVT RT was an independent predictor of the SF-36 PCS (full model R(2) = 0.331, p = 0.003). PVT lapse was also an independent predictor of the SF-36 PCS (full model R(2) = 0.320, p = 0.004). However, neither PVT RT nor lapse was a significant independent predictor of the SF-36 mental component summary score (MCS). Only CES-D was an individual predictor of the SF-36 MCS (β = -0.676, p < 0.001). Impairments in sustained attention and vigilance may underlie the limitations in physical health-related quality of life reported by people with OSA, even after controlling for demographic variables, apnea severity, and depression.

Fatigue in sleep apnea: the role of depressive symptoms and self-reported sleep quality

OBJECTIVES OR BACKGROUND: Obstructive Sleep Apnea (OSA) is characterized by partial or complete cessation of breath during sleep. OSA is associated with increased cardiovascular risk as well as psychosocial complications such as daytime somnolence, depression, and fatigue. The goal of the present study was to better understand fatigue in OSA by examining self-reported sleep quality, depressive symptoms, excessive daytime sleepiness, and OSA severity in a group of newly diagnosed OSA patients.

METHODS

Two hundred and forty newly diagnosed OSA patients enrolled in the study. Participants completed several questionnaires at baseline.

RESULTS

Depressive symptoms accounted for 15% of variance in fatigue beyond that of demographics and OSA severity (p<0.001). Self-reported sleep quality accounted for 11% of variance beyond that of depressive symptoms (p<0.001). The total model accounted for 48% of the variance in fatigue. Post hoc analysis found that the total model accounted for only 14% of the variance in sleepiness (as measured by the Epworth Sleepiness Scale).

CONCLUSION

The current study confirms the findings of previous OSA studies, which found depressive symptoms have a greater association with fatigue than OSA disease severity variables. This study extends those findings by showing that self-reported sleep quality is independently associated with fatigue, even after taking into account demographic, comorbid conditions, OSA disease severity, sleepiness, and depressive symptoms. The role of sleep quality as an independent contributor to daytime fatigue in OSA may be under appreciated. Sleep quality should be closely followed in the clinical management of OSA.

Macrophage migratory inhibitory factor (MIF) may be a key factor in inflammation in obstructive sleep apnea

STUDY OBJECTIVES

This study investigated the 24-hour variation of macrophage migratory inhibitory factor (MIF), a cytokine which induces insensitivity to the anti-inflammatory effects of glucocorticoids, in patients with untreated obstructive sleep apnea (OSA) as compared to healthy adults with no OSA.

PARTICIPANTS

Fifty-three men and women with OSA (mean apnea/hypopnea index [AHI] = 39.5) and 24 healthy adults (Non-OSA, AHI = 5.1).

MEASUREMENTS

Over a 24-h period, blood was collected every 2 h for MIF and cortisol determination. The following night, sleep was monitored with polysomnography.

RESULTS

MIF showed a strong 24-h variation, with a peak at 04:00 and a nadir at 22:00. Patients with OSA showed 25% higher MIF levels (area under the curve) over 24 h than healthy controls. Furthermore, MIF levels were significantly associated with AHI and total arousal index (ArI), even after adjusting for BMI. Cortisol showed the expected 24-h variation (peaking at 06:00), but no cortisol differences were observed between OSA and Non-OSA groups.

CONCLUSION

MIF is elevated in patients with OSA and is related to OSA severity, while there was no difference in cortisol levels. MIF is a pro-inflammatory cytokine which additionally inhibits the anti-inflammatory effects of glucocorticoids. Thus, elevated MIF levels in OSA may contribute to elevated inflammation.

Effects of continuous positive airway pressure on fatigue and sleepiness in patients with obstructive sleep apnea: data from a randomized controlled trial

OBJECTIVES

Complaints of fatigue are frequent in patients with obstructive sleep apnea (OSA); however, the impact of continuous positive airway pressure (CPAP) on fatigue remains unclear.

METHODS

Fifty-nine men and women with OSA were randomly assigned to therapeutic or placebo CPAP in a double-blind fashion for a 3-week intervention period. Four outcome measures were assessed: (1) fatigue/vigor measured with the Multidimensional Fatigue Symptom Inventory--Short Form (MFSI-sf), the (2) fatigue and (3) vigor subscales of the Profile of Mood States--Short Form (POMS), and (4) the Epworth Sleepiness Scale (ESS). Data were analyzed using repeated-measures analysis of variance.

RESULTS

Compared with patients receiving placebo CPAP, those patients treated with therapeutic CPAP showed significant reductions in the apnea-hypopnea index, as well as decreases in both measures of fatigue and increases in vigor (P values < 0.05). The beneficial effect of therapeutic treatment was most pronounced in patients with high levels of fatigue at study onset. Significant treatment effects in sleepiness scores were not observed in the entire sample (P > 0.05); however, in a subset of patients with excessive sleepiness at the onset of treatment, ESS scores were significantly reduced with use of therapeutic CPAP (P < 0.05).

CONCLUSIONS

Results suggest that 3 weeks of therapeutic CPAP significantly reduced fatigue and increased energy in patients with OSA. Therapeutic CPAP significantly reduced daytime sleepiness in patients who reported excessive sleepiness at the onset of treatment.

Sleep health in U.S. Hispanic population

The importance of sleep on health has only been recently recognized, and the general public and the medical community are not yet fully knowledgeable about this issue. The great majority of sleep research has been performed in whites of European descent and to a lesser extent in African Americans, making generalization of the findings to other ethnic and racial groups difficult. Very little sleep research has been done in U.S. Hispanics. However, based on the available literature and the high prevalence of risk factors in Hispanics, such as obesity, diabetes, living in the inner city, and use of alcohol, the prevalence of such important sleep disorders such as obstructive sleep apnea and sleep habits such as poor sleep hygiene are suspected to be high. There is also some evidence that acculturation to the U.S. life style may lead to worse sleep habits in Hispanics, including fewer hours of sleep. Two current large NIH sponsored studies of sleep in U.S. Hispanics promise to significantly add to the literature on various sleep disorders such as sleep disordered breathing, insomnia, restless legs syndrome, periodic limb movement disorder, and sleep habits such as short sleep duration and sleep hygiene.

Continuous positive airway pressure deepens sleep in patients with Alzheimer's disease and obstructive sleep apnea

OBJECTIVE

Patients with Alzheimer's disease (AD) and obstructive sleep apnea (OSA) experience disrupted sleep. This study examined the effect of continuous positive airway pressure (CPAP) on sleep parameters in AD patients with OSA.

METHODS

A randomized placebo-controlled trial of 3 weeks of therapeutic CPAP (tCPAP) vs. 3 weeks placebo CPAP (pCPAP) followed by 3 weeks tCPAP in patients with AD and OSA. Polysomnography data from screening after one night and after 3 weeks of treatment were analyzed. Records were scored for percent of each sleep stage, total sleep time (TST), sleep efficiency (SE), sleep period (SP), time in bed (TIB), sleep onset (SO), wake time after sleep onset (WASO), and arousals. A randomized design comparing one night of pCPAP to tCPAP and a paired analysis combining 3 weeks of tCPAP were performed.

RESULTS

Fifty-two participants (mean age=77.8 years, SD=7.3) with AD and OSA were included. After one treatment night, the tCPAP group had significantly less % Stage 1 (p=0.04) and more % Stage 2 sleep (p=0.02) when compared to the pCPAP group. In the paired analysis, 3 weeks of tCPAP resulted in significant decreases in WASO (p=0.005), % Stage 1 (p=0.001), arousals (p=0.005), and an increase in % Stage 3 (p=0.006).

CONCLUSION

In mild to moderate AD patients with OSA, the use of tCPAP resulted in deeper sleep after just one night, with improvements maintained for 3 weeks.

Sustained use of CPAP slows deterioration of cognition, sleep, and mood in patients with Alzheimer's disease and obstructive sleep apnea: a preliminary study

INTRODUCTION

Obstructive sleep apnea (OSA) is common among patients with Alzheimer's disease (AD). Untreated OSA exacerbates the cognitive and functional deficits. Continuous positive airway pressure (CPAP) has recently been shown to have beneficial effects on cognition in AD. Little attention has focused on the long-term benefits of CPAP in these patients.

METHODS

This was an exploratory study of sustained CPAP use (mean use = 13.3 months, SD = 5.2) among a subset of participants from an initial 6-week randomized clinical trial (RCT) of CPAP in patients with mild to moderate AD. Follow-up included 5 patients who continued CPAP (CPAP+) after completion of the RCT and 5 patients who discontinued CPAP (CPAP-), matched by time of completion of the initial study. A neuropsychological test battery and sleep/mood questionnaires were administered and effect sizes were calculated.

RESULTS

Even with a small sample size, sustained CPAP use resulted in moderate-to-large effect sizes. Compared to the CPAP- group, the CPAP+ group showed less cognitive decline with sustained CPAP use, stabilization of depressive symptoms and daytime somnolence, and significant improvement in subjective sleep quality. Caregivers of the CPAP+ group also reported that their own sleep was better when compared to the final RCT visit and that their patients psychopathological behavior was improved.

CONCLUSION

The results of this preliminary study raise the possibility that sustained, long-term CPAP treatment for patients with AD and OSA may result in lasting improvements in sleep and mood as well as a slowing of cognitive deterioration. Prospective randomized controlled research trials evaluating these hypotheses are needed.

Caffeine intake is independently associated with neuropsychological performance in patients with obstructive sleep apnea

In healthy individuals, caffeine intake may improve performance on cognitive tests. Obstructive sleep apnea (OSA) is a disorder that has been associated with impaired cognitive function. In this study, we investigated whether increased caffeine intake in untreated patients with OSA is linked to better cognitive performance. Forty-five untreated OSA patients underwent baseline polysomnography after completing a survey of 24-h caffeine intake. Participants completed a battery of neuropsychological tests, then demographically corrected T scores and a global deficit score (GDS) were calculated on these tests. Partial correlation analysis was performed to compare daily caffeine intake with GDS, after controlling for body mass index (BMI) and sleep apnea severity. Analysis of covariance was done to examine differences in daily caffeine intake between cognitively impaired (GDS >or= 0.5) and non-impaired (GDS < 0.5) individuals. Seven out of the 45 subjects met the criteria (GDS >or= 0.5) for cognitive impairment. There was a significant inverse association between caffeine intake and the GDS, both when controlling for BMI (r =or -0.331, p = 0.04) and when controlling for BMI and apnea severity (r =or-0.500, p = 0.002); those with less impairment consumed more caffeine. Analysis of covariance demonstrated that cognitively impaired individuals consumed one-sixth as much caffeine as non-impaired individuals (p < 0.05). In patients with moderately severe OSA, higher average daily caffeine intake was associated with less cognitive impairment.

Cognitive effects of treating obstructive sleep apnea in Alzheimer's disease: a randomized controlled study

OBJECTIVES

To examine whether treatment of obstructive sleep apnea (OSA) with continuous positive airway pressure (CPAP) in patients with Alzheimer's disease (AD) results in better cognitive function.

DESIGN

Randomized double-blind placebo-controlled trial. Participants were randomized to therapeutic CPAP for 6 weeks or placebo CPAP for 3 weeks followed by therapeutic CPAP for 3 weeks.

SETTING

General clinical research center.

PARTICIPANTS

Fifty-two men and women with mild to moderate AD and OSA.

INTERVENTION

CPAP.

MEASUREMENTS

A complete neuropsychological test battery was administered before treatment and at 3 and at 6 weeks.

RESULTS

A comparison of subjects randomized to 3 weeks of therapeutic versus placebo CPAP suggested no significant improvements in cognition. A comparison of pre- and posttreatment neuropsychological test scores after 3 weeks of therapeutic CPAP in both groups showed a significant improvement in cognition. The study was underpowered to make definitive statements about improvements within specific cognitive constructs, although exploratory post hoc examination of change scores for individual tests suggested improvements in episodic verbal learning and memory and some aspects of executive functioning such as cognitive flexibility and mental processing speed.

CONCLUSION

OSA may aggravate cognitive dysfunction in dementia and thus may be a reversible cause of cognitive loss in patients with AD. OSA treatment seems to improve some cognitive functioning. Clinicians who care for patients with AD should consider implementing CPAP treatment when OSA is present.

The obesity-hypoventilation syndrome and respiratory failure in the acute trauma patient

BACKGROUND

The Emergency Department experience, for many patients, involves procedures and therapies that can compromise ventilation. In the acute trauma patient, these include spinal immobilization, supine positioning, and the administration of sedative and analgesic medications. Patients with the obesity-hypoventilation syndrome have a syndrome distinct from mere obesity, and are more sensitive to these insults.

OBJECTIVE

To describe a case of respiratory failure in a patient with the obesity-hypoventilation syndrome resulting from injuries and therapies that in any other patient would not be expected to cause respiratory failure.

CASE REPORT

A 59-year-old woman suffered a mechanical fall, fractured her T6 vertebral body and right proximal humerus, and, after spinal immobilization and the administration of routine doses of opioid analgesics, suffered significant hypoxemia and respiratory acidosis. Reversal agents were ineffective, but non-invasive mechanical ventilation restored adequate respiration.

CONCLUSION

Although obesity-hypoventilation syndrome occurs in only a minority of morbidly obese patients, it is important because the consequences of respiratory failure can be severe if not recognized and anticipated. Such patients will not be able to adequately increase ventilation in response to mounting hypercapnia. The condition is easily addressed through non-invasive ventilation.

Serum aminotransferase levels are associated with markers of hypoxia in patients with obstructive sleep apnea

STUDY OBJECTIVES

Nonalcoholic fatty liver disease (NAFLD) is a disorder that often presents with elevated serum aminotransferase levels. Although it has classically been linked with the metabolic syndrome, recent studies suggest NAFLD may also be associated with obstructive sleep apnea (OSA). This study evaluates the association between serum aminotransferase levels and factors connected with: either the metabolic syndrome (elevated body mass index [BMI], lipid profile, blood pressure, fasting glucose), or with OSA severity (apnea hypopnea index, lowest oxygen saturation level, oxygen desaturation index, percent of time below 90% saturation [%T<90]).

DESIGN

Retrospective case series.

PATIENTS AND SETTING

109 adult patients with OSA at a university hospital general clinical research center.

MEASUREMENTS AND RESULTS

Markers of hypoxia (lowest oxygen saturation level and %T<90), correlated significantly with aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels (Pearson's r = -0.31 to -0.38, P <0.003), while apnea hypopnea index, body mass index, blood pressure, fasting glucose, triglyceride, and cholesterol levels did not. Hierarchical linear regression was then done to determine the best predictors of aminotransferase levels. Markers of metabolic syndrome were entered as one block and markers of sleep apnea as another. Regression analyses explained 16.3% of the variance in AST and 18.9% of the variance in ALT, with %T<90 playing the largest role.

CONCLUSIONS

In patients with obstructive sleep apnea, serum aminotransferase levels are better predicted by markers of oxygen desaturation than by factors traditionally associated with the metabolic syndrome.

Neuropsychological effects of 2-week continuous positive airway pressure treatment and supplemental oxygen in patients with obstructive sleep apnea: a randomized placebo-controlled study

STUDY OBJECTIVES

To determine predictors of neuropsychological functioning in patients with obstructive sleep apnea (OSA) and whether treatment with 2-week continuous positive airway pressure (CPAP) or supplemental oxygen would improve cognitive functioning.

DESIGN

Randomized placebo-controlled design.

SETTING

University-based clinical research center.

PATIENTS

Forty-six patients with untreated OSA.

INTERVENTIONS

Two-week CPAP, supplemental oxygen, or placebo-CPAP.

MEASUREMENTS AND RESULTS

Participants underwent polysomnography and completed a neuropsychological test battery before and after treatment. Prior to treatment, patients with OSA showed diffuse impairments, particularly in terms of speed of information processing, attention and working memory, executive functioning, learning and memory, as well as alertness and sustained attention. A global deficit score at baseline was positively correlated with percentage of stage 1 sleep (p = .049) only and was not correlated with obesity, daytime sleepiness, depression, fatigue, OSA severity, and the other polysomnography variables. The 3 treatment groups (therapeutic-CPAP, supplemental oxygen, and placebo-CPAP) were compared using repeated-measures analysis of variance (ANOVA). There was no significant Time x Treatment interaction for the global deficit score. When examining individual neuropsychological test scores, two thirds of them improved with time regardless of treatment, although only Digit Vigilance-Time (p = .020) showed significant improvement specific to CPAP treatment.

CONCLUSION

The present results suggest that Digit Vigilance-Time might be the most sensitive neuropsychological test for measuring the effects of the treatments. In general, 2 weeks of CPAP or oxygen-supplementation treatment was insufficient to show overall beneficial cognitive effects, as compared with placebo-CPAP. However, 2 weeks of CPAP treatment might be helpful in terms of speed of information processing, vigilance, or sustained attention and alertness.

Effects of 2-week nocturnal oxygen supplementation and continuous positive airway pressure treatment on psychological symptoms in patients with obstructive sleep apnea: a randomized placebo-controlled study

Psychological symptom improvement has been observed after continuous positive airway pressure (CPAP) treatment of obstructive sleep apnea (OSA). Because CPAP normalizes both sleep disruption and oxyhemoglobin desaturation, the mechanism of psychological symptom improvement is unclear. Using a 3-arm placebo-controlled design, we parsed out the separate effects of treatment on psychological symptoms. OSA patients (N = 38) were monitored 2 nights with polysomnography and then randomized to 2-weeks therapeutic CPAP, placebo CPAP, or O(2) supplementation. Pre and post-treatment, patients completed the Brief Symptom Inventory (BSI): Higher scores indicate greater severity. Repeated measures analysis of covariance reveals a Time x Treatment interaction for BSI Global Severity Index (GSI): significant pre- to post-treatment reductions in GSI with O(2) supplementation and therapeutic CPAP, but not placebo CPAP. A Time x Treatment interaction was also found for depression: Depression decreased with O(2) supplementation but not with therapeutic CPAP or placebo CPAP. Both therapeutic CPAP and O(2) supplementation resulted in decreased psychological symptoms. Results suggest hypoxemia may play a stronger role than sleep disruption vis-à-vis OSA related psychological distress.

The effect of sleep-disordered breathing on stages of sleep in patients with Alzheimer's disease

Patients with Alzheimer's disease (AD) commonly have poor sleep and a high reported incidence of sleep-disordered breathing (SDB). This study examined how the presence of SDB affected sleep stages in AD patients. Sixty-six volunteers with mild - moderate AD underwent home polysomnography. Results showed that patients with SDB spent less of the night in REM sleep than those with no SDB, but there were no differences in other sleep stages. The findings suggest that the decreased amount of REM sleep may be due to the presence of AD and SDB. Treating these patients' SDB may increase their amount of REM sleep, which may result in improved daytime functioning. Controlled trials of SDB treatment in AD are needed to answer this question.

Continuous positive airway pressure reduces subjective daytime sleepiness in patients with mild to moderate Alzheimer's disease with sleep disordered breathing

OBJECTIVES

Studies have reported that 33% to 70% of patients with Alzheimer's disease (AD) have sleep-disordered breathing (SDB). Continuous positive airway pressure (CPAP) treatment has been shown to reduce daytime sleepiness and improve health-related quality of life in nondemented older people with SDB. The effect of therapeutic CPAP treatment on daytime sleepiness in patients with mild-moderate AD with SDB was assessed.

DESIGN

Randomized, double-blind, placebo-controlled trial.

SETTING

Patients' home and the University of California San Diego, General Clinical Research Center, J. Christian Gillin Laboratory of Sleep and Chronobiology.

PARTICIPANTS

Thirty-nine community-dwelling elderly patients with mild-moderate probable AD with SDB.

INTERVENTION

Patients were randomly assigned to receive 6 weeks of therapeutic CPAP or 3 weeks of sham CPAP followed by 3 weeks of therapeutic CPAP.

MEASUREMENTS

Epworth Sleepiness Scale (ESS) was administered at baseline, 3 weeks, and 6 weeks. Changes in daytime sleepiness in subjects who received optimal therapeutic CPAP were compared with changes in the sham CPAP group.

RESULTS

Within the therapeutic CPAP group, ESS scores were reduced from 8.89 during baseline to 6.56 after 3 weeks of treatment (P=.04) and to 5.53 after 6 weeks of treatment (P=.004). In the sham CPAP group, there was no significant difference after 3 weeks of sham CPAP but a significant decrease from 7.68 to 6.47 (P=.01) after 3 weeks of therapeutic CPAP.

CONCLUSION

These data provide evidence of the effectiveness of CPAP in reducing subjective daytime sleepiness in patients with AD with SDB.

Adherence to continuous positive airway pressure treatment in patients with Alzheimer's disease and obstructive sleep apnea

OBJECTIVE

This analysis examined whether patients with Alzheimer disease (AD) tolerate continuous positive airway pressure (CPAP).

METHOD

Thirty patients with AD were randomized to CPAP or sham CPAP and completed sleep, depression, and quality-of-life questionnaires. Participants could choose to continue treatment after the trial.

RESULTS

Patients wore CPAP for 4.8 hours per night. More depressive symptoms were associated with worse adherence (rS=-0.37; N=30, p<0.04). Patients who continued using CPAP had fewer depressive symptoms (t [19]=2.45, p=0.02) and better adherence (t [19]=2.32, p=0.03) during the trial.

CONCLUSION

Patients with AD with obstructive sleep apnea can tolerate CPAP. Adherence and long-term use may be more difficult among those patients with more depressive symptoms.

Acetylcholinesterase Inhibitors and Sleep Architecture in Patients with Alzheimer???s Disease

BACKGROUND AND OBJECTIVE

Studies suggest that some acetylcholinesterase inhibitors (AChEIs) increase rapid eye movement (REM) sleep and nightmares in patients with Alzheimer's disease (AD) but few have studied their effect on other sleep parameters. The objective of this study was to examine differences in sleep architecture in AD patients taking different AChEIs.

METHODS

76 participants (51 men, 25 women) [mean age = 78.2 years; SD = 7.7] with mild to moderate AD underwent medication history screening as well as polysomnography to determine the percentage of each sleep stage. Participants were divided into groups based on AChEI used: donepezil (n = 41), galantamine (n = 15), rivastigmine (n = 8) or no AChEI (n = 12). General univariate linear model analyses were performed.

RESULTS

AChEI therapy had a significant effect on the percentage of stage 1 (p = 0.01) and stage 2 (p = 0.03) sleep. Patients in the donepezil group had a significantly lower percentage of stage 1 sleep than patients in the galantamine group (mean = 17.3%, SD = 11.7 vs 29.2%, SD = 15.0, respectively; p = 0.01), but there was no significant difference between the donepezil group and the rivastigmine (mean = 25.0%, SD = 12.3) or no AChEI groups (mean = 27.6%, SD = 17.7) in this respect. No significant differences in percentage of stage 1 between other groups were seen. Patients in the donepezil group also had a significantly higher percentage of stage 2 sleep than patients in the no AChEI group (mean = 63.6%, SD = 14.4 vs 51.4%, SD = 16.9, respectively; p = 0.04), but there was no significant difference between the donepezil group and either the galantamine group (mean = 56.5%, SD = 8.7) or the rivastigmine group (mean = 59.9%, SD = 8.4). There were no significant differences between groups in terms of percentage REM sleep or other sleep parameters.

CONCLUSION

Subgroups of AD patients (classified according to AChEI treatment) in this study differed with respect to the amount of stage 1 and stage 2 sleep experienced, with the donepezil-treated group having the lowest percentage of stage 1 sleep and the highest percentage of stage 2 sleep. There was no significant difference in the amount of REM sleep between the groups. Our data suggest that sleep architecture may be affected by the use of donepezil in patients with AD. Although not elicited in this study because of the small sample size, there may be a class effect of AChEIs on sleep architecture. Double-blind, placebo-controlled studies are needed to better understand causality and the effect of each AChEI on sleep architecture in patients with AD.

Effects of nasal continuous positive airway pressure and oxygen supplementation on norepinephrine kinetics and cardiovascular responses in obstructive sleep apnea

Obstructive sleep apnea (OSA) is characterized by noradrenergic activation. Nasal continuous positive airway pressure (CPAP) is the treatment of choice and has been shown to effectively reduce elevated norepinephrine (NE) levels. This study examined whether the reduction in NE after CPAP is due to an increase in NE clearance and/or a decrease of NE release rate. Fifty CPAP-naive OSA patients with an apnea-hypopnea index >15 were studied. NE clearance and release rates, circulating NE levels, urinary NE excretion, and blood pressure and heart rate were determined before and after 14 days of CPAP, placebo CPAP (CPAP administered at ineffective pressure), or oxygen supplementation. CPAP led to a significant increase in NE clearance ( P ≤ 0.01), as well as decreases in plasma NE levels ( P ≤ 0.018) and daytime ( P < 0.001) and nighttime ( P < 0.05) NE excretion. NE release rate was unchanged with treatment. Systolic ( P ≤ 0.013) and diastolic ( P ≤ 0.026) blood pressure and heart rate ( P ≤ 0.014) were decreased in response to CPAP but not in response to oxygen or placebo CPAP treatment. Posttreatment systolic blood pressure was best predicted by pretreatment systolic blood pressure and posttreatment NE clearance and release rate ( P < 0.01). The findings indicate that one of the mechanisms through which CPAP reduces NE levels is through an increase in the clearance of NE from the circulation.

The association between interleukin-6, sleep, and demographic characteristics

We examined the relationship between the pro-inflammatory cytokine IL-6 and sleep architecture in 70 healthy men and women. Blood was drawn in the early morning for assessment of IL-6 followed by nocturnal sleep monitoring with polysomnography. Sleep records were scored for sleep stages using standard criteria. Morning IL-6 levels were positively correlated with REM latency after sleep onset [rho = .31, p = .01], percent (%) stage 1 sleep [rho = .23, p = .053], % wake after sleep onset (WASO) [rho = .29, p<.05]. IL-6 levels were negatively correlated with sleep efficiency [rho = -.36, p<.01] and slow wave sleep (SWS) [rho = -.26, p<.05]. After controlling for demographic variables including race, gender, age, and BMI, multiple hierarchical regression analyses revealed that morning IL-6 levels accounted for a significant portion of the variance of REM latency (p<.01), sleep efficiency (p<.01), and % WASO (p = .01). IL-6 was no longer associated with % stage 1 sleep, SWS, and total sleep time after controlling for the demographic characteristics. These findings suggest that the inflammatory marker IL-6 is associated with sleep quality and that certain individual characteristics such as race, gender, and age modify that relationship. Higher IL-6 levels were associated with lower quality of sleep among healthy asymptomatic men and women.

Blood pressure variability in obstructive sleep apnea: role of sympathetic nervous activity and effect of continuous positive airway pressure

BACKGROUND

Many studies support a link between obstructive sleep apnea (OSA), increased blood pressure (BP) and/or BP variability, and sympathetic nervous system (SNS) activity. We assessed the relationship between SNS activity and 24-h BP variability in patients with OSA, and the effect of continuous positive airway pressure (CPAP) on BP variability.

DESIGN

Forty-one patients with a respiratory disturbance index (RDI) > 15 were randomized into CPAP or CPAP placebo groups for a 1-week trial.

METHODS

Ambulatory BP, 24-h urine norepinephrine (NE) and polysomnography were measured prior to treatment and after 1 and 7 days of treatment.

RESULTS

Neither RDI nor 24-h urine NE levels were related to 24-h mean BP levels. While RDI was associated only with night-time BP variability, daytime urine NE levels were associated with both night-time and daytime BP variability. After treatment, the BP variability decreased significantly but equally in both active and placebo CPAP groups.

CONCLUSIONS

Obstructive sleep apnea is more related to BP variability than BP. Sympathetic nervous activity, as inferred from daytime urine NE, is related to changes in BP variability in OSA patients. BP variability is not specifically affected by CPAP.

Autonomic and cardiovascular function in postmenopausal women: the effects of estrogen versus combination therapy

OBJECTIVE

This study examined the effects of oral estrogen (ERT) alone versus oral estrogen/medroxyprogesterone acetate (HRT) therapy on cardiovascular function, as controlled by the autonomic nervous system.

STUDY DESIGN

Forty-three postmenopausal women received ERT, HRT, or a placebo for 3 months in a double-blind, randomized, placebo-controlled study. Cardiovascular hemodynamics and heart rate variability were assessed at rest and during stress.

RESULTS

After 3 months of therapy, oral HRT significantly increased high-frequency power (P =.0002) and decreased total peripheral resistance (P =.04). The changes were evident at rest and during stress.

CONCLUSION

Our findings suggest that combination therapy produces a more favorable alteration of autonomic cardiovascular function than estrogen alone (ie, combination therapy increases vagal activity).

Sleep quality and blood pressure dipping in obstructive sleep apnea

BACKGROUND

Obstructive sleep apnea (OSA) is associated with poor sleep quality and a high incidence of nondipping. The aim of this study was to determine the association of sleep quality and nocturnal blood pressure (BP) dipping in an OSA population.

METHODS

A total of 44 untreated subjects with mild to severe OSA underwent overnight-attended polysomnography and 24-h ambulatory BP monitoring. Subjects were off antihypertensive medication. The percentage of slow wave sleep, percentage of time awake after sleep onset during the sleep period, sleep efficiency, and arousal index were chosen as measurements of sleep quality. Dipping was evaluated using the change in systolic BP, diastolic BP, and mean arterial pressure. Patients were classified as dippers and nondippers based on a nocturnal drop in mean arterial pressure > 10%. Differences between groups were evaluated by independent sample t tests. Pearson correlation and linear regression were used to evaluate the association of sleep quality and dipping.

RESULTS

There were no differences between dippers and nondippers with regard to body mass index, age, or respiratory disturbance index. A total of 84% were nondippers. No difference was found between dippers and nondippers in sleep quality. None of the sleep quality measures correlated with the measurements of dipping. In multiple regression analyses, the percentage of slow wave sleep and arousal index each independently predicted only a small percentage of the variance (approximately 10%) of nocturnal DBP dipping.

CONCLUSIONS

The prevalence of nondipping was very high in a population of untreated patients with mild to severe OSA. Nonetheless, sleep quality did not appear to be related to BP dipping.

Effect of continuous positive airway pressure and placebo treatment on sympathetic nervous activity in patients with obstructive sleep apnea

STUDY OBJECTIVES

We studied the effect of continuous positive airway pressure (CPAP) treatment on sympathetic nervous activity in 38 patients with obstructive sleep apnea.

DESIGN

Randomized, placebo-controlled trial.

SETTING

Patients underwent polysomnography on three occasions in a clinical research center, and had BP monitored over 24 h at home. All of the patients had sleep apnea with a respiratory disturbance index (RDI) > 15.

INTERVENTIONS

The patients were randomized blindly to CPAP or placebo (CPAP at ineffective pressure) treatment.

MEASUREMENTS AND RESULTS

Prior to therapy, the number of apneas and the severity of nocturnal hypoxia correlated significantly with daytime urinary norepinephrine (NE) levels, but not nighttime urinary NE levels. CPAP treatment lowered daytime BP from 99 +/- 2 mm Hg to 95 +/- 3 mm Hg (mean +/- SEM) and nighttime BP from 93 +/- 3 mm Hg to 88 +/- 3 mm Hg. Placebo CPAP treatment decreased both day and night mean BP only 2 mm Hg. CPAP, but not placebo, treatment lowered daytime plasma NE levels by 23%, daytime urine NE levels by 36%, daytime heart rate by 2.6 beats/min, and increased lymphocyte beta(2)-adrenergic receptor sensitivity (all p < 0.05). The effect of CPAP treatment on nighttime urine NE levels and heart rate did not differ from placebo treatment. There was a suggestion of an effect of placebo CPAP treatment on nighttime measures, but not on daytime measures.

CONCLUSION

We conclude that daytime sympathetic nervous activation is greater with more severe sleep apnea. CPAP treatment diminished the daytime sympathetic activation; the potential nighttime effect of CPAP treatment was obscured by a small placebo effect.

Obstructive sleep apnea and hypertension: are peripheral chemoreceptors involved?

The mechanism of pathogenesis of hypertension in patients with obstructive sleep apnea (OSA) is unknown. Many investigators point to the high sympathetic nervous system activity (SNS) observed in OSA patients. However, there is no clear explanation as to the mechanism for the development of SNS hyperactivity in these patients. A common feature of patients with OSA is repetitive bouts of transient hypoxemia during sleep. Repetitive transient hypoxemia in rats has resulted in hypertension. In OSA patients, resolution of nocturnal hypoxemia with CPAP has corrected nocturnal and diurnal hypertension. Also, exposure to hyperoxia reduces blood pressure and sympathetic activity in OSA patients, but not in normals. These data suggest a significant role of peripheral chemoreceptors in the regulation of vascular tone. We hypothesize that peripheral chemoreceptors significantly contribute to the pathogenesis of hypertension in patients with OSA and that this is associated with chemoreceptor hyperactivity. This implies that correcting the intermittent nocturnal hypoxemia alone may prevent the cardiovascular morbidity associated with obstructive sleep apnea.