Effects of Nocturnal Hypertension on Sleep Quality in Renal Transplant Recipients

Hypertension affects the great majority of renal transplant recipients (RTR) and its persistence may negatively influence the outcome of the graft. Unfortunately, its diagnosis is not univocal since office measurement of blood pressure (BP) may reveal a "white coat hypertension" in normotensive subjects, or might not detect hypertension if pills are taken immediately before BP control. Therefore for a correct diagnosis the use of ambulatory BP monitoring (ABPM) is strongly advised. Recent studies employing this methodology have shown that the prevalence of nocturnal hypertension (i.e. blood pressure values >120/70 or 10% higher than diurnal values) affects a great number of renal transplant recipients (RTR), even despite the use of antihypertensive drugs ("non-dipper" patients). It is well known that nocturnal hypertension enhances the development of cardiovascular diseases, but it is not clear whether (and to what extent) it also affects the quality of sleep of these patients. Sleep disturbances like insomnia, restless legs syndrome and sleep apnoea, in fact, are particularly common in RTR, despite these patients report significantly better quality of life compared to patients with chronic renal failure under conservative or dialysis treatment. The working hypothesis of the present study is to evaluate whether any relationship exists between nocturnal hypertension and sleep quality, since also sleep disorders may favour the onet and the progression of cardiovascular diseases, the first cause of death in RTR with functioning graft.

The study will be carried out on all the available RTR in regular follow-up at the DH of Nephrology and Renal Transplantation of the University Federico II of Naples (Italy). Inclusion criteria are: age >18 years, renal transplant vintage >1 year, stable renal function in the last 6 month, no change in immunosuppressive nor antihypertensive treatment in the last 3 months, no intercurrent infection in the last 3 months. Twenty-four hour ABPM will be performed during the regular follow-up of patients in the investigator's Unit. Hypertension will be diagnosed when the patient takes antihypertensive drugs or when his . BP is >130/80 mmHg (24-hour average value), or >135/85 (average values of daily BP) or >120/70 (average values of nocturnal BP). The patient will be considered "non-dipper" when the ratio Systolic nocturnal BP/Systolic diurnal BP is >0.9.

Sleep quality will be evaluated through a validated version of the Pittsburgh Sleep Questionnaire a self-rated questionnaire, consisting of 19 questions which assess a wide variety of factors relating to sleep quality, including estimates of sleep duration and latency and of frequency and severity of specific sleep-related problems. These 19 items are grouped into seven-component scores, each weighted equally on a 0-3 scale. The seven components are then summed to yield a global index (PSQI) ranging between 0 and 21; higher scores indicate a worse sleep quality (>5, poor sleepers; <5, good sleepers). The seven components of the PSQI are subjective sleep quality, sleep latency, sleep duration, habitual sleep efficiency, sleep disturbances, use of sleeping medications, and daytime dysfunction. The relationship between nocturnal hypertension and sleep quality will be evaluated either by bivariate analysis and by multiple linear regression analyses. In the multivariate model, all the variables associated to an elevated night/day systolic pressure ratio will be considered if the P value is 0.10 or less at bivariate analysis. The relationship between increased night/day SBP ratio and increased PSQI will be also investigated by multivariate logistic regression model.