Hypothesis / aims of study
The relation between nocturia and nighttime systolic blood pressure (SBP) is bidirectional. Elevated nighttime SBP increases the odds of nocturia by 64%, conversely, nocturia is independently associated with elevated nighttime SBP and the degree of elevation is directly related to the frequency of nocturia. Poor sleep often coexists with nocturia and both are known to increase nighttime systolic blood pressure (SBP) which results in poor daytime blood pressure control, loss of the circadian dip in nighttime blood pressure (i.e. nighttime dipping), and adverse cardiovascular outcomes. The effect of behavioral sleep intervention and chronotherapy (switching antihypertensive to bedtime dosing) on nighttime nondipping or daytime blood pressure control in older adults is unclear. We conducted pilot randomized controlled trial to study the above interventions.
Study design, materials and methods
We randomized 30 healthy community-dwelling older adults (age, 72±5 years; 57% women) on non-diuretic daily antihypertensive medication and awaken ≥2 times nightly to void to one of 3 groups i) control: continuing morning antihypertensive dosing, ii) behavioral sleep intervention (BBTI- brief behavioral treatment of insomnia) while continuing with morning antihypertensive dosing, or iii) chronotherapy: switch their non-diuretic antihypertensive to bedtime dosing for 6-weeks. All participants completed three-day bladder diary to assess nocturia, nighttime urine volume (NUV), and nocturnal polyuria index (NPi:% of 24h urine volume excreted during sleep). Participants concurrently wore a single-channel, EEG device Zmachine® for objective in-home sleep assessment. Time in bed and total sleep time were obtained from Zmachine®, sleep efficiency was calculated as the percentage of total sleep time to time in bed. Subjectively, sleep was assessed using insomnia severity index (ISI). Mean awake and asleep SBP were obtained using an ambulatory BP monitor. Nocturnal dipping was calculated as the percent difference between the mean SBP while awake and during sleep.
Results
BBTI had greater decreases compared to chronotherapy and controls in nocturia (-0.6 vs -0.3 vs 0.3), NPi (-6.0 vs -0.9 vs 0.5), and ISI score (-4.5 vs -3.7 vs -0.7); and increases in sleep efficiency (12 vs -3 vs -7) and nocturnal SBP dip (7.3 vs 3.9 vs -0.4) based on descriptive statistics. In BBTI, the decrease in nocturia frequency correlated with decline in awake SBP (r=0.69, p=0.03) and asleep SBP (r=00.59, p=0.07), and reduced NPi correlated with nighttime dipping in SBP (r=0.75, p=0.01). Increase in sleep efficiency correlated with a decline in awake SBP (r=-0.78, p=0.01), asleep SBP (r=-0.82, p=0.003), and nighttime SBP dipping (r=0.62, p=0.06). Total sleep time increase also correlated with increased nocturnal SBP dipping (r=0.66, p=0.04). Both BBTI and chronotherapy groups demonstrated a significant nighttime dipping of SBP post-intervention (BBTI p=0.04, chronotherapy p<0.01, control p=0.07). All groups demonstrated tolerability with intervention without any complaints of lightheadedness or falls with nighttime awakenings during the study duration.
Interpretation of results
Interventions were well tolerated without any falls or other adverse events. Behavioral sleep intervention not only improved sleep, but also increased nighttime dipping, decreased nocturia and improved several other bladder and sleep parameters including NPi, sleep efficiency and total sleep time. Improvements in sleep, nocturia frequency, and nighttime urine production correlated with improved awake as well as asleep SBP and increased nighttime SBP dipping. The sleep and chronotherapy interventions tested can affect both blood pressure control and nighttime dipping due to their effect on sleep and nocturia.