Effect of Antihypertensive Medications on the Severity of Obstructive Sleep Apnea: A Systematic Review and Meta-Analysis

STUDY OBJECTIVES

Obstructive sleep apnea (OSA) is an independent risk factor for hypertension (HTN). Increasing evidence from animal and human studies suggests that HTN exacerbates OSA. We performed a systematic review and meta-analysis of studies evaluating the effect of anti-hypertensive medications on the severity of OSA.

METHODS

A literature search of PubMed and Embase was done using search concepts of OSA, HTN, and drug classes used to treat HTN. Studies that reported changes in the severity of OSA objectively by using apnea-hypopnea index (AHI) or respiratory disturbance index (RDI) were included. Pooled mean difference estimates were calculated. Tests for heterogeneity, publication bias, and subgroup sensitivity analysis were conducted.

RESULTS

Of 27,376 studies screened, only 11 met inclusion criteria, including 5 randomized controlled trials and 6 single-arm prospective trials. The pooled mean difference estimate (95% confidence interval [CI]), based on a random-effects model, was -5.69 (95% CI -10.74 to -0.65), consistent with an overall decrease in AHI or RDI attributable to antihypertensive medications. The effect size was even more pronounced, -14.52 (95% CI -25.65 to -3.39), when only studies using diuretics were analyzed. There was no significant heterogeneity or publication bias among the studies. Meta-regression indicated neither age, baseline AHI, nor change in systolic/diastolic blood pressure influenced the results.

CONCLUSIONS

Collectively, findings from these relatively small, short-term studies tend to support the contention that treatment with antihypertensive agents confers a statistically significant, albeit small, reduction in the severity of OSA, which may be more pronounced with the use of diuretics.

Is reduced cell size the mechanism for shrinkage of the adrenal zona reticularis in aging?

In aging humans, corticosteroid production is preserved, or even increased, but there is an unexplained reduction in adrenal androgen secretion that likely has significant health implications. Preliminary analyses on adrenocortical morphology have revealed an age-associated reduction in the thickness of the zona reticularis (ZR), the cortical zone responsible for the majority of DHEA/DHEA sulfate production in the adult human, but no change in the overall thickness of the adrenal cortex. The ZR width could decrease in aging due to loss of ZR cells and/or to shrinkage of ZR cells. In the current study, we investigated whether there was a relation between thickness of the zona reticularis in young and old humans and the cell density in this zone. Paraffin-embedded sections of the adrenal cortex of 10 young (21-35 yr old) and 10 old (54-89 yr old) adults who had died suddenly as the result of trauma were stained with hematoxylin and eosin. These specimens were chosen from a larger cohort of samples for having a broad ZR in the young group and a narrower ZR in the older group. After determining the overall cortical thickness and the width of the ZR by use of computerized image analysis software, we counted the number of adrenocortical cells in two random high power fields of the ZR of each specimen. The ZR width of the older group (57 +/- 7 arbitrary units, Mean +/- SE) was significantly reduced compared to that of the young group (124 +/- 21), P < 0.001. On the other hand, the overall cortical width in the old group (232 +/- 17) was similar to that of the young adults (249 +/- 38). In the old group, the ZR comprised 24.7 +/- 3% of the total cortical width, whereas it was 50 +/- 2% of the cortical width in the young adrenals, P < 0.001. The cell density (cell number/60 x high power field) of the ZR of old adults (83 +/- 9) was similar to that of the young group (87 +/- 5). In summary, although the width of the ZR regresses with aging, cell size in this zone is preserved. Therefore, loss of trophic support for ZR cells would not appear to be the explanation for zonal shrinkage in aging. Rather, it is likely that aging effects may be due to increased cell loss in the ZR or else reduced rates of differentiation/migration of cells into this cortical zone.