Epidemiologic studies show that patients with OSA have a high prevalence of obesity.2,11 Therefore, obesity may be the nexus that explains the high prevalence of hypertension in these patients. However, the results of a large, prospective, longitudinal study, the Wisconsin Sleep Cohort Study (WSCS), suggest that moderate to severe OSA (apnea-hypopnea index [AHI] ≥ 15/h) is an independent cause of hypertension. Subjects with this degree of OSA severity showed a 3.2-fold increase in the odds of developing hypertension, compared with subjects without OSA.12 The WSCS results impacted the American guidelines for the management of hypertension (The Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure [JNC VII]), and OSA was recognized as the first secondary cause of hypertension.13 Similarly, Marin et al14 conducted an observational study that included 1,889 subjects without hypertension who were admitted to a sleep clinic and were followed up for a mean of 10.1 years. The authors found an increased incidence of hypertension in subjects with untreated OSA, compared with treated patients. Other studies have shown that age, somnolence, and sex could influence and modulate this independent relation. Bixler et al15 examined 741 men and 1,000 women aged 20 to 100 years and found that the strength of the association between OSA and hypertension may become attenuated with age. Haas et al16 confirmed these results and established a cutoff age of 60 years. Above this age, the strength of the association declines. Conversely, the results of a 5-year follow-up of participants in the Sleep Heart Health Study (SHHS),17 after adjusting for BMI, did not confirm the independent relationship between OSA and hypertension found in the Wisconsin cohort.