Endocrine Abstracts

Background: HIV-infected patients are predisposed to an increased risk of hyponatremia. In healthy population, low sodium is associated with impaired health status and reduced BMD, but less is known about this association in HIV-infection.

Aim: To investigate the relationship between serum sodium, frailty and BMD in a large cohort of HIV-infected patients.

Methodology: A retrospective, observational, cohort study on adult HIV-infected patients (age ≥18 years), attending the Multidisciplinary Metabolic Clinic of Modena, was carried out including all sodium examinations performed at the Modena lab from 2007 to 2017 available in a large database. Laboratory ranges of normality for sodium (136–146 mEq/l) were used to subdivide records in hyponatremic (HypoNa), hypernatremic (HyperNa) and normonatremic (NormoNa) groups. BMD was measured at total body, lumbar spine (L1–L4) and total hip using a Hologic QDR-2000 densitometer (DXA). Frailty was calculated through 38-item multimorbidity frailty index.

Statistical analysis: Parameters were not normally distributed and Kruskal-Wallis test, followed by Dunn’s test, was used to compare continuous variables. Correlations were performed using linear regression models.

Results: 8101 records (5454 from males and 2647 from females) of serum sodium (mean 139.4±3.1 mEq/l) evaluated in HIV-infected patients (mean age 49.0±7.9 years) were considered. 617 (7.6%), HypoNa, 44 (0.5%) HyperNa and 7440 (91.8%) NormoNa were found. Frailty score was inversely related to serum sodium (r=−0.174, R²=0.03, P<0.0001), even after the exclusion of HyperNa group (R=−0.191, R²=0.036, P<0.0001). Frailty was significantly higher in HypoNa than NormoNa (P<0.001). Considering results at DXA examination, BMD was normal in 30.3% and reduced in 69.7% (54.8% osteopenia, 14.9% osteoporosis). Total body BMD, but not femoral nor lumbar, directly correlated with serum sodium (R=0.049, P<0.001) and it was significantly lower in HypoNa compared to NormoNa (P=0.029).

Conclusions: This study shows that serum sodium is inversely related to frailty, suggesting its potential role as reliable and cheap marker in the HIV-infection follow-up. Furthermore, we demonstrate a direct correlation between sodium and body BMD in HIV-infected patients, similarly to general population.