Prevalence of hyponatraemia in geriatric hip fracture patients in rural India: a one-year retrospective observational cohort study

Background: Hip fractures are a major cause of morbidity, functional decline and healthcare burden in older adults. Hyponatraemia is common in hospitalized older patients and has been associated with falls, fractures and adverse perioperative outcomes. Evidence from rural Indian hip-fracture cohorts is limited. Differences in access to care, timing of presentation, comorbidity burden and continuity of follow-up may influence the burden of hyponatraemia and early outcomes in such settings. The aim is to determine the prevalence of admission hyponatraemia among patients aged ≥60 years with radiologically confirmed hip fractures treated at a rural tertiary care teaching hospital in Maharashtra, India, and to assess its association with postoperative complications, length of hospital stay and 30-day readmission. Methods: This retrospective observational cohort study included 150 eligible patients aged 60 years or older with radiologically confirmed hip fractures and an admission serum sodium result during January-December 2024. Admission sodium was classified as normal (≥135 mmol/l) or hyponatraemic (<135 mmol/l); severity was described as mild (130-134 mmol/l), moderate (125-129 mmol/l) or severe (<125 mmol/l). Categorical variables were compared using Pearson chi-square or Fisher exact tests, and length of stay was compared using the Mann-Whitney U test. Effect estimates are unadjusted; 95% confidence intervals are reported where applicable. Results: Admission hyponatraemia was present in 44/150 patients (29.3%; 95% CI 22.6%-37.1%) using the biochemical threshold of serum sodium <135 mmol/l. Among these 44 patients, 28 (63.6%) had mild, 12 (27.3%) moderate and 4 (9.1%) severe hyponatraemia. Postoperative complications were recorded in 16/44 (36.4%) patients with hyponatraemia and 20/106 (18.9%) with normal sodium (unadjusted RR 1.93, 95% CI 1.11-3.36; p=0.022). Median hospital stay was 9.0 versus 8.0 days (Mann-Whitney U=1522.5; p<0.001). Thirty-day readmission was recorded in 6/44 (13.6%) versus 11/106 (10.4%) (unadjusted RR 1.31, 95% CI 0.52-3.33; Fisher exact p=0.579). Diabetes mellitus was more frequent in the hyponatraemic group. Three records with sodium exactly 135 mmol/l were coded as mild in the source severity field; they were classified as normonatraemic for this analysis, consistent with the prespecified threshold <135 mmol/l. Conclusions: Admission hyponatraemia was present in 29.3% of this single-centre rural/peri-urban Indian geriatric hip-fracture cohort when defined as serum sodium <135 mmol/l. In unadjusted analyses, it was associated with more recorded postoperative complications and longer hospital stay; 30-day readmission did not differ significantly. Because the study was retrospective and no multivariable adjustment was performed, these findings do not establish independent effects or causality. The results should be interpreted within the cohort eligibility criteria and data limitations.