Sleep Quality Depends not only on Blood Pressure, but also on Numerous other Influencing Factors

We were interested to read the article by Tairu et al. on a cross-sectional study of subjective sleep quality and blood pressure in 169 people with an optimal sleep duration of 6-8h per night [1] .Half of the subjects reported poor sleep quality [1] .The higher the blood pressure, the worse the sleep quality [1] .It was concluded that subjective poor sleep quality is associated with increased blood pressure [1] .The study is remarkable, but some points should be discussed.The first point is that sleep quality depends not only on blood pressure, but on many other influencing factors, especially comorbidities [2] .These include neurological diseases (e.g.seizures, ischemic stroke, Parkinson's disease, restless legs syndrome, central sleep apnoea syndrome, neuropathic pain, sympathetic/parasympathetic activation), cardiovascular diseases (e.g.heart failure, coronary heart disease, cardiac arrhythmia, heart failure, coronary heart disease), lung diseases (e.g.chronic obstructive pulmonary disease (COPD), asthma, pulmonary hypertension), urological diseases (e.g.pollakissuria, nocturia), orthopaedic diseases (e.g.musculoskeletal pain, chronic fatigue syndrome), gastroenterological diseases (e.g.nausea, gastritis, reflux, flatulence, diarrhea, constipation), immunological diseases (e.g.arthritis, colitis, Crohn's disease), endocrinological diseases (e.g.hyperhidrosis, menopause), electrolyte disorders and malignant diseases.The second point is that sleep quality is also strongly influenced by endogenous (e.g.genetic background, personality structure, temperament, lifestyle, pattern of social interactions, social status, processing of daytime experiences before and during sleep, fixed or variable bedtime, type and intensity of dreams, acute and chronic stress load, expected events and planned tasks for the coming days) and exogenous factors (e.g.climate zone, eating habits, timing of water and food intake, intake of illicit drugs, consumption of adrenergic stimulants (nicotine, caffeine, cola, Red Bull)), abuse of alcohol or illegal drugs, level of physical activity, noise at the sleeping place (neighbours, street, dogs, refrigerator, air conditioning, telephones), humidity, noise at the workplace, brightness of the room (screens, blinking sensors), temperature and draughts in the bedroom, degree of air pollution (urban or rural area), vibrations (traffic, disco, earthquake) and electrosmog [2] .All these influencing factors must be included in the assessment before poor sleep quality is attributed solely to arterial hypertension or high blood pressure.The third point is that the quality of sleep also depends on the current medication.Medications that strongly influence sleep quality include not only hypnotics, but also sedatives, antidepressants, neuroleptics, steroids, adrenergics, antiepileptics, antiparkinsonian drugs, beta-blockers, cholinesterase inhibitors (e.g.donepezil, rivastigmine, galantamine), decongestants and caffeine-containing drugs [3] .Therefore, it would have been imperative to consider the entire co-medication of the cohort.The fourth point is that sleep quality depends on blood pressure only when hypertension has become symptomatic.If there is no eye pain, no headache and no dizziness, sleep is usually not disturbed.Therefore, we should know how many of the people included had symptomatic hypertension and how many had asymptomatic hypertension.The fifth point is that blood pressure in the included patients was measured between 8 am and 4 pm, but not during the night [1] .Therefore, the relationship between blood pressure and sleep quality is not reliable.Blood pressure should have been measured either before sleep or during sleep.Even better would have been a 24-hour blood pressure measurement to determine whether blood pressure was really elevated before or during sleep.As a rule, blood pressure drops during the night [4] .To summarize, this interesting study has limitations that affect the results and their interpretation.Addressing these limitations could strengthen the conclusions and support the message of the study.All open questions need to be clarified before readers uncritically accept the conclusions of the study.Sleep quality depends not only on blood pressure, but also on numerous other