Nighttime Blood Pressure in Normotensive Subjects With Chronic Insomnia: Implications for Cardiovascular Risk

OBJECTIVE: To assess as whether insomniacs have higher nighttime blood pressure (BP) and a blunted day-to-night BP reduction, recognized markers of increased risk of cardiovascular morbidity and mortality. DESIGN: Prospective case-control study. SETTING: University hospital-based sleep research laboratory. PARTICIPANTS: Thirteen normotensive subjects with chronic primary insomnia (9 women, 42 +/- 7 y) and 13 sex- and age-matched good sleepers. MEASUREMENTS AND RESULTS: Subjects underwent 2-week sleep diary and 3 sleep studies to provide subjective and objective sleep variables, and 24-h beat-to-beat BP recording to provide daytime, night-time and day-to-night BP changes (nighttime-daytime/daytime)*100) (BP dipping). Spectral analysis of the electroencephalogram (EEG) was also performed during sleep of night 3 to assess EEG activity in the beta frequency (16-32 Hz), a measure of brain cortical activation. Nighttime SBP was higher (111 +/- 15 vs 102 +/- 12 mm Hg, P < 0.01) and day-to-night SBP dipping was lower (-8% +/- 6% vs -15% +/- 5%, P < 0.01) in insomniacs than good sleepers. Insomniacs also had higher activity in EEG beta frequency (P < 0.05). Higher nighttime SBP and smaller SBP dipping were independently associated with increased EEG beta activity (P < 0.05). CONCLUSIONS: Higher nighttime SBP and blunted day-to-night SBP dipping are present in normotensive subjects with chronic insomnia and are associated with a hyperactivity of the central nervous system during sleep. An altered BP profile in insomniacs could be one mechanism implicated in the link between insomnia and cardiovascular morbidity and mortality documented in epidemiological studies.