THE ASSOCIATION BETWEEN HYPERTENSION AND SLEEP-APNEA IN OBESE PATIENTS

Strong associations have been demonstrated between hypertension (HTN) and obesity, and obesity and sleep apnea (SA). However, it is unclear whether previously suggested relationships between HTN and SA were bas ed on causal mechanisms, or rather, were confounded by obesity. To inv estigate whether SA may be an independent predictor of HTN, we measure d respiration during sleep and BP in 19 participants in a hospital-bas ed weight control program. Additionally, subjects underwent cephalomet ry, measurement of weight and hip circumferences, and pulmonary functi on tests. Studies were repeated in 14 subjects following weight loss. Subjects consisted of 9 men and 10 women, ages 43 +/- 11 years (mean /- SD), and weight of 114 +/- 20 kg. Hypertension (diastolic BP >95 mm Hg, systolic BP >160 mm Hg, or a report of current use of an antihype rtensive medication) was present in 6 (32 percent) subjects. Sleep apn ea was more prevalent among the hypertensive (5/6; 83 percent) than no rmotensive (2/13; 15 percent) subjects (p<0.01); respiratory disturban ce index (RDI) was 42.4 +/- 16.0 vs 6.2 +/- 2.3 (p<0.01) in these grou ps. Compared with normotensive subjects, hypertensive subjects were of similar weight, but had greater central obesity and had lower levels of vital capacity. Regression analyses demonstrated that RDI was the s trongest independent predictor of BP level, accounting for approximate ly 60 percent of the variability in this measurement. Following weight loss, BP and RDI both significantly declined, soft palate width decre ased, and vital capacity increased. Thus, in this group of obese subje cts, BP level was associated most significantly with the magnitude of sleep-related respiratory disturbances. The obese subjects who are mos t likely to have SA and HTN are male and/or subjects with greater cent ral obesity and lower vital capacity.