Peripheral Resistance to Arginine Vasopressin and Its Relationship with Plasmaosmolarityinaged Population

Abstract

Background: The causes of age-related poor urine concentration capacity favouring low-grade chronic dehydration in aged populations are not well understood. Objectives: To explore links between age and plasma and urine osmolarity levels and a possible picture of peripheral resistance to arginine vasopressin (R-AVP) in an aged population. Design: observational cross-sectional study. Study population: communitydwelling subjects aged 70 years and older. Data collection: Blood and urine samples collected after 10 hours night fasting were analysed for osmolarity and copeptin levels (AVP surrogate). R-AVP was established based on a urinary osmolarity/copeptin ratrio<35. Results: 237 subjects were recruited (mean age 75.7 years, 52.7% women). Plasma osmolarity was similar between the sexes and age groups (70-79 and ≥80 years); whereas urine osmolarity was lower in women and in the older age group. Plasma hyperosmolarity (>295 mOsm/L) was present in no women and in 4.5% of men, and was significantly 14 times greater in the older group. R-AVP prevalence was 12.7% in the younger group vs 20.7% in the older group (p=0.252). Subjects with R-AVP, compared to without R-AVP, presented higher plasma osmolarity (287.6 vs 285.4 mOsm/L; p=0.023) and higher prevalence of plasma hyperosmolarity (8.7% and 0.7%; p=0.053). R-AVP was also related with IL-6 and creatinine levels and with loop diuretic use. Conclusions: Urine concentration capacity decreases and plasma hyperosmolarity increases after the age of 80 years. Fourteen percent of ≥70 year’s old population present R-AVP, which greatly increases the risk of plasmahyperosmolarity and is related with loop diuretic use, and IL-6 and creatinine levels.