Sleep Quality in Non Dialysis Chronic Kidney Disease: Associated Factors and Influence on Prognosis

Abstract

Deficient sleep quality (SQ) has been linked with a higher hospitalization rate and mortality in dialysis patients, however the prevalence of sleep disorders and their influence on prognosis in non-dialysis chronic kidney disease (CKD) has been poorly investigated. The aim of this study was to assess factors related with SQ in CKD patients (stages I-IV) followed in a nephrology outpatient clinic as well as the long-term impact of SQ on patient's outcome. Between January and May 2008, Pittsburgh Sleep Quality Index (PSQI) was self-administered by 122 patients (68 males and 54 females) with a mean age of 65 years. Patients were classified as "good" (global PSQI < 6) and "poor" sleepers (global PSQI ≥ 6). We identified 66 (54%) poor sleepers (PS), characterized by an older age (66 ± 14.2 vs 57 ± 17.0, p < 0.01), female predominance (59% vs 26%, p < 0.01) and worse renal function (49 ± 19.1 vs 57 ± 23.2 ml/min, p < 0.05). There was a significant correlation between phosphate and PSQI score (r = 0.234, p = 0.01), however no correlation with calcium or PTH. Vitamin D was also lower in PS (17 ± 7.2 vs 23 ± 15.1 ng/ml, p < 0.05). Until June 2015, hospitalization rate was higher among PS (64% vs 44%, p < 0.05). In this period, there was also a trend towards higher mortality for PS (18% vs 16%). In summary, over 50% of CKD patients have poor SQ, which was associated with older age, female gender, worse renal function, lower vitamin D and higher phosphate levels. Deficient sleep was associated with a greater probability of hospitalization and might be a prognostic marker in CKD.