Poor sleep with normal sleep duration: a preventive effect on incident hypertension.

To the Editor: I have recently read with interest the article by FernandezMendoza et al concerning the predictive ability of insomnia with objective short sleep duration for the incidence of hypertension. They also described that poor sleepers who slept ≥6 hours showed a reduced risk for incident hypertension. Although they mentioned that the findings were consistent with their past findings by quoting their reference, there is no clear description that poor sleep with normal sleep duration relates to lower risk of hypertension. Wang et al recently conducted a meta-analysis on the association between sleep duration and hypertension, and long sleep duration was also a risk of prevalent hypertension among subjects <65 years of age. Furthermore, Yoshioka et al reported in a crosssectional study that there was a positive association between sleep duration and arterial stiffness using brachial-ankle pulse-wave velocity, although Drager and Lorenzi-Filho required much more information to establish the association. I suppose that there is no clear evidence to understand the effect of poor sleep with normal sleep duration on the lower risk of hypertension. The percent of poor sleepers with normal sleep duration was 14.3% of total population, and there is a possibility of change in sleep state by long period of time. But Fernandez-Mendoza et al measured sleep duration by using sleep polysomnography, and I think this procedure is worthy for maintaining the validity of the study. I recommend a longer follow-up study to check the validity of the effect of poor sleep with normal sleep duration on the incident hypertension.