Cross-sectional study on relationships between hypertension and insomnia

Introduction Hypertension (HT) and insomnia seem to be associated but, to date, only few studies have described this relationship. Insomnia seems to represent an independent factor influencing the negative outcome of HT while other studies indicate, although non-consistently, a possible negative influence of anxiety/depression on HT.Objective of this study is to determine relationships between insomnia and HT, taking into account also anxiety/depression factors. Materials and methods In this cross-sectional cohort study, 270 consecutive essential hypertensive patients were recruited at the Outpatient Hypertension Unit, University of Pisa, Italy. Pittsburgh Sleep Quality Index (PSQI), Insomnia Severity Index (ISI), Beck Depression Inventory (BDI), Perceived Stress Scale (PSS), Self-Rating Anxiety Scale (SAS) and State-Trait Anxiety Inventory (STAI-Y2) were administered to all subjects. Patients with Sleep-Disordered Breathing were excluded. Possible associations between HT, insomnia and anxiety/depression factors were evaluated using a statistical approach based on Principal Components Analysis (PCA). Results After varimax rotation, PCA allowed us identifying two principal components which explain 35% and 24% of variance respectively: 1) PC1, named Insomnia Factor, includes PSQI 1, 2, 3, 4, 5 factors, ISI, and sleep duration (SD) (SD is negatively correlated with PC1 while the other parameters are positively correlated); PC2, named Anxiety/Depression Factor, includes PSQI 6 and 7 components, BDI, SAS, STAI and PSS (all positively correlated with PC2). The study of clinical degree of HT allowed us disentangling Non Resistant HT patients (NRHT, No: 230; 51% males) from Resistant HT patients (RHT, No: 40; 51% females). Thus, Kruskal–Wallis test with Resistant HT as between factor has been computed on both PC1 and PC2. RHT patients showed significantly higher Insomnia Factor (PC1) values than NRHT ones (p < 0.01). No significant difference has been detected for Anxiety/Depression Factor (PC2). Interestingly, differences identified for the Insomnia Factor show a gender effect: RHT females show significantly higher values with respect to NRHT ones, while no significant difference (p < 0.15) is apparent for males. Conclusion These preliminary results allowed us to draw two main conclusions: (i) insomnia and anxiety/depression status are independent factors in modulating HT; (ii) insomnia is significantly associated with resistance to treatment in hypertensive women, independently of any other psychological confounders.In conclusion, the promising results of this study will help to develop specific therapeutic strategies towards Resistant Hypertension, which should include hypnotic treatment.