Heritability of OSA in a Rural Population.

BACKGROUND: OSA has a familial aggregation pattern indicating that it can be partially caused by a genetic component. However, the heritability of OSA has been estimated based on the study of families of obese probands of urban populations with established OSA diagnosis. The objective of this genetic-epidemiologic study is to study families ascertained from a general rural population to determine an unbiased estimate of OSA heritability. METHODS: We studied a sample of families living in Baependi, a small rural southeastern Brazilian city. Participants were assessed for anthropometric measurements, physical examination, Epworth Sleepiness Scale, blood samples for glucose and cholesterol determination, and overnight home portable monitoring. RESULTS: We studied 587 participants (399 women) from 91 families, with a median (interquartile range [IQR]) of 4 (2-8) participants per family. The median age of the population was 44 years (IQR, 29-55 years) and median BMI was 25.0 kg/m(2) (IQR, 22.1-28.6 kg/m(2)). OSA, defined by apnea-hypopnea index (AHI) > 5/h, was diagnosed in 18.6% of the sample. Two polygenic models, model I (no covariate effects) and model II (with covariate effects), were fitted to the data in all analyses. Heritability estimates for AHI were 0.23 and 0.25 for model I and II, respectively. Covariates (age, sex, and BMI) showed no significant effects on the heritability estimate for AHI. CONCLUSIONS: The heritability of AHI in a rural population with low levels of obesity is intermediate (25%).

Effects of OSA treatment on BP in patients with resistant hypertension: a randomized trial.

BACKGROUND: OSA is extremely common among patients with resistant hypertension (HTN). However, the impact of the treatment of OSA with CPAP on BP in patients with resistant HTN is not well established. METHODS: In the current study, 40 patients with confirmed resistant HTN and moderate to severe OSA confirmed by full polysomnography were randomized to medical therapy or to medical treatment plus CPAP for 6 months. Patients were evaluated at study baseline and after 6 months by 24-h ambulatory BP monitoring (ABPM). RESULTS: Thirty-five patients (77% men; age, 56 ± 1 years; BMI, median 32 kg/m² [25%-75%, 28-39 kg/m²]; apnea-hypopnea index, 29 events/h [24-48 events/h]; Epworth Sleepiness Scale, 10 ± 1; systolic/diastolic office BP, 162 ± 4/97 ± 2 mm Hg; taking four [four to five] antihypertensive drugs) completed the study. CPAP was used for 6:01 ± 0:20 h/night (3:42-7:44 h/night). Compared with the control group, awake systolic/diastolic ABPM decreased significantly in the CPAP group (Δ: +3.1 ± 3.3 /+2.1 ± 2.7 mm Hg vs -6.5 ± 3.3/-4.5 ± 1.9 mm Hg, respectively, P < .05). Interestingly, the BP changes were observed only while patients were awake, but not during nocturnal ABPM (Δ: +2.8 ± 4.5/+1.8 ± 3.5 mm Hg vs +1.6 ± 3.5/+0.8 ± 2.9 mm Hg, P = NS). CONCLUSIONS: The treatment of OSA with CPAP significantly reduces daytime BP in patients with resistant HTN. Therefore, our study reinforces the importance of recognizing and treating OSA in patients with resistant HTN. TRIAL REGISTRY: ClinicalTrials.gov; No.: NCT00812695; URL: www.clinicaltrials.gov.

Obstructive sleep apnea: the most common secondary cause of hypertension associated with resistant hypertension.

Recognition and treatment of secondary causes of hypertension among patients with resistant hypertension may help to control blood pressure and reduce cardiovascular risk. However, there are no studies systematically evaluating secondary causes of hypertension according to the Seventh Joint National Committee. Consecutive patients with resistant hypertension were investigated for known causes of hypertension irrespective of symptoms and signs, including aortic coarctation, Cushing syndrome, obstructive sleep apnea, drugs, pheochromocytoma, primary aldosteronism, renal parenchymal disease, renovascular hypertension, and thyroid disorders. Among 125 patients (age: 52±1 years, 43% males, systolic and diastolic blood pressure: 176±31 and 107±19 mm Hg, respectively), obstructive sleep apnea (apnea-hypopnea index: >15 events per hour) was the most common condition associated with resistant hypertension (64.0%), followed by primary aldosteronism (5.6%), renal artery stenosis (2.4%), renal parenchymal disease (1.6%), oral contraceptives (1.6%), and thyroid disorders (0.8%). In 34.4%, no secondary cause of hypertension was identified (primary hypertension). Two concomitant secondary causes of hypertension were found in 6.4% of patients. Age >50 years (odds ratio: 5.2 [95% CI: 1.9-14.2]; P<0.01), neck circumference ≥41 cm for women and ≥43 cm for men (odds ratio: 4.7 [95% CI: 1.3-16.9]; P=0.02), and presence of snoring (odds ratio: 3.7 [95% CI: 1.3-11]; P=0.02) were predictors of obstructive sleep apnea. In conclusion, obstructive sleep apnea appears to be the most common condition associated with resistant hypertension. Age >50 years, large neck circumference measurement, and snoring are good predictors of obstructive sleep apnea in this population.