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In a large prospective cohort study of nearly 2000 patients studied for over a
decade, Marin and colleagues found that compared with participants without OSA,
the presence of OSA was associated with increased adjusted risk of incident hyper-
tension; however, treatment with CPAP therapy was associated with a lower risk of
hypertension [ 8 ]. A large meta-analysis of 16 trials also supported a small but statis-
tically significant effect of CPAP on both systolic (−2.5 mmHg) and diastolic
(−1.8 mmHg) blood pressures [ 60 ] although the short duration of PAP therapy
(<24 weeks across studies) may have led to an underestimate of its true impact. A
more recent meta-analysis of 28 trials showed similar results, with reductions in
systolic (−2.58 mmHg) and diastolic (−2.01 mmHg) blood pressures favoring PAP
treatment [ 60 ]. In a long-term study of patients with OSA and HTN randomized to
either CPAP or conservative treatment, those adherent with CPAP usage for at least
5.6 h per night were found to have significant reductions in blood pressure at 1-year
follow-up [ 61 ]. Another trial examining the effects of CPAP in hypertensive patients
over a year found that CPAP facilitated de-escalation of the antihypertensive treat-
ment in 71% of subjects with resistant hypertension, but had no effect on the num-
ber of antihypertensives required by the controlled group [ 62 ].
Effect of CPAP on Resistant Hypertension
Studies suggest that CPAP may affect blood pressure more strongly in those OSA
patients with resistant hypertension than in the general population of hypertensive
patients. For instance, a meta-analysis focusing specifically on patients with resis-
tant hypertension found an even stronger effect, with reductions in systolic BP by
3 mmHg and in diastolic BP by 5 mmHg on average [ 63 ].
The recent HIPARCO trial further supports the notion that CPAP may be espe-
cially effective in patients with resistant hypertension [ 64 ]. This multicenter ran-
domized controlled trial of nearly 200 patients with OSA of at least moderate
severity (AHI ≥ 15 using 4% hypopnea criteria) was randomized to 12 weeks of
CPAP versus no CPAP. Patients were taking an average of 3.8 antihypertensive
drugs per patient and had a mean AHI of 40 events/hr. In an intention-to-treat analy-
sis, those who used CPAP regularly experienced statistically significant reductions
in 24-h mean blood pressure by 4.4 mmHg, respectively, in a per-protocol analysis
and a 14% increase in the percentage of patients with a normal nocturnal blood
pressure dipper pattern at 12 weeks. There was a dose-response relationship between
the hours of CPAP use and the degree of 24-h mean blood pressure reduction,
whereby each additional hour of CPAP use translated into a 2 mmHg reduction in
systolic and 1 mmHg reduction in diastolic blood pressure. It is notable that since
patients with a history of poor antihypertensive medication adherence were excluded
from this study, these results may have magnified the benefits of CPAP relative to
the general population.
Another small randomized study of patients with resistant hypertension and at
least moderate OSA randomized to either CPAP or sham-CPAP for 8 weeks found
the CPAP promoted a 5 mmHg greater reduction in systolic blood pressure [ 65 ].
L.A. Tobias and F. Roux