Hypertension and sleep apnea in black South Africans - A case control study

Despite relatively consistent findings that patients with hypertension have higher than anticipated prevalences of sleep apneal/hypopnea (SAH), inadequately controlled factors such as age and obesity have been implicated as possibly accounting for these findings. All-night polysomnograms were performed on 20 hypertensive black South Africans, a group with increased risk for this disease. They were matched with a control group of black subjects in respect of age, gender, body mass index (BMI), neck circumference and scores on a sleep questionnaire. While the groups failed to differ significantly in terms of demographic variables, nor in regard to 8/9 anthropometric measures, the hypertensive group had a significantly higher apneal/hypopnea index (AH) (P =.01), longer duration of AH (P =.01) and lower mean minimum arterial oxygen saturation levels (P =.005). Of the anthropometric measures, only age and neck circumference were found to be cofactors for AHI and were accounted for in the analysis. Five of the hypertensive patients and two of the controls had an AHI >10, giving a prevalence odds ratio of 3 (95% confidence interval: 0.66-14.50). The present study appears to be the first in black African subjects and with prevalence findings largely comparable to those obtained in other ethnic groups. There was a trend for more severe SAH to occur in this subgroup of five hypertensives (AHI - 14-30) than in controls (maximum AHI = 12). While data are lacking to link antihypertensive medication to SAH in humans, further study is necessary before discarding this factor.