Differing relationship of nocturnal fluid shifts to sleep apnea in men and women with heart failure

In men with heart failure, nocturnal rostral fluid shift is associated with an overnight increase in the neck circumference (NC) and with severity of obstructive sleep apnea. Because the prevalence of obstructive sleep apnea is lower in women than in men with heart failure, we hypothesized that less fluid would shift into the neck in association with less severe obstructive sleep apnea in women than in men with heart failure. In 35 men and 30 women with heart failure, we assessed overnight changes in NC (ΔNC) and leg fluid volume before and after polysomnography. The severity of obstructive sleep apnea was assessed by the apnea-hypopnea index. Although the changes in leg fluid volume did not differ significantly between men and women (-131 ± 90 versus -180 ± 132 mL, P=0.081), in women, ΔNC was smaller (P