Background: 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.
Methods and results: 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<0.001) than in men. Furthermore, although in men, changes in leg fluid volume correlated inversely with ΔNC (r=-0.755, P<0.001) and apnea-hypopnea index (r=-0.765, P<0.001), it did not in women.
Conclusions: Despite no difference in overnight displacement of fluid from the legs compared with in men, in women, less of this fluid reached the neck, and unlike men, there was no relationship between changes in leg fluid volume and either ΔNC or apnea-hypopnea index. These findings suggest a differing relationship between overnight fluid shift from the legs and severity of obstructive sleep apnea in women than in men with heart failure.