Reliability of orthostatic beat-to-beat blood pressure tests: implications for population and clinical studies

Objective: To assess the test–retest reliability of orthostatic beat-to-beat blood pressure responses to active standing and related clinical definitions of orthostatic hypotension. Methods: A random sample of community-dwelling older adults from the pan-European Survey of Health, Ageing and Retirement in Europe, Ireland underwent a health assessment that mimicked that of the Irish Longitudinal Study on Ageing. An active stand test was performed using continuous blood pressure measurements. Participants attended a repeat assessment 4–12 weeks after the initial measurement. A mixed-effects regression model estimated the reliability and minimum detectable change while controlling for fixed observer and time of day effects. Results: A total of 125 individuals underwent repeat assessment (mean age 66.2 ± 7.5 years; 55.6% female). Mean time between visits was 84.3 ± 23.3 days. There was no significant mean difference in heart rate or blood pressure recovery variables between the first and repeat assessments. Minimum detectable change was noted for changes from resting values in systolic blood pressure (26.4 mmHg) and diastolic blood pressure (13.7 mmHg) at 110 s and for changes in heart rate (10.9 bpm) from resting values at 30 s after standing. Intra-class correlation values ranged from 0.47 for nadir values to 0.80 for heart rate and systolic blood pressure values measured 110 s after standing. Conclusion: Continuous orthostatic beat-to-beat blood pressure and related clinical definitions show low to moderate reliability and substantial natural variation over a 4–12-week period. Understanding variation in measures is essential for study design or estimating the effects of orthostatic hypotension, while clinically it can be used when evaluating longer term treatment effects

Night, darkness, sleep, and cardiovascular activity.

We humans tend to spend a significant fraction of the night asleep in the dark and to stay awake with daylight. However, the widespread availability of electrical power is progressively imparting 24/7 activity schedules to our modern societies, in which artificial ambient light and illuminated screens of electronic devices allow people to stay awake at night for work or leisure, postponing sleep. Sleep disorders such as insomnia and sleep-disordered breathing may reduce the quantity and quality of nocturnal sleep and entail excessive daytime sleepiness as a consequence. Not only these environmental and behavioral factors but also a range of genetic, epigenetic, and age-dependent factors may cause the body to be regulated out of phase with the environment, mimicking in many respect conditions of jet lag associated with long-range flights. This chapter will discuss the effects of night/day, darkness/light, and sleep/wakefulness on cardiovascular activity considering firstly each factor on its own and secondly the interactions among the different factors. The chapter will focus on the control of arterial blood pressure and heart rate in human subjects. The chapter will also touch upon the hemodynamic consequences of the control of vascular resistance and blood volume, as well as upon the bidirectional translation between research on human subjects and model organisms such as mice, which are arguably the mammals of choice for mechanistic studies of functional genomic

Other syndromes of orthostatic intolerance : Delayed orthostatic hypotension, postprandial hypotension, postural orthostatic tachycardia syndrome, and reflex syncope

Apart from classical orthostatic hypotension, the gravitational force may strongly contribute to other forms of orthostatic intolerance, delayed and postprandial OH, postural orthostatic tachycardia syndrome (POTS), and reflex syncope. In delayed OH, the significant blood pressure drop occurs first after 3-min period of orthostasis, whereas in postprandial OH, the symptoms appear first approximately 15-30 min after the meal. POTS is rarely seen in older adults and presents as abnormal sinus tachycardia on standing with symptoms of orthostatic intolerance, dizziness, fatigue, and cognitive impairment. Reflex syncope may manifest as orthostatic vasovagal reflex, situational syncope, or carotid sinus hypersensitivity, which becomes a clinical syndrome when associated with history of unexplained syncope and positive provocation test, carotid sinus massage. Older patients with a history of orthostatic intolerance, unexplained syncope and fall trauma, and negative result of active standing test should be further evaluated using cardiovascular autonomic tests such as head-up tilt testing, Valsalva maneuver, and carotid sinus massage