Prevalence of hyponatremia among elderly patients at the Moi Teaching and Referral Hospital, Eldoret, Kenya

Abstract

Introduction: Hyponatremia refers to a serum sodium level of less than 135mmol/L, and can be classified into various ways based on severity, tonicity, chronicity and volume status, with the most common and of clinical significance being hypotonic hyponatremia. It is the most common electrolyte abnormality in the elderly. Multiple factors are usually implicated in the development of hyponatremia in the elderly such as the low salt diet as recommended by clinicians, aging-related impaired water excretory capacity, and frequent comorbidities with exposure to medications. Considering all its etiologies, it is a factor of poor prognosis and is associated with increased hospital stay and institutionalization of the elderly. There is a growing size of elderly population in Kenya. However, the prevalence of hyponatremia in Kenya and sub-Saharan Africa is not well defined. Therefore, there is need for epidemiological data for evidence based early screening and diagnosis for successful management to prevent adverse outcomes. Objective: To determine the prevalence, subtypes and factors associated with hyponatremia among the elderly patients. Methods: This was a cross-sectional study conducted at the Moi Teaching and Referral Hospital (MTRH). The study population was all elderly patients aged ≥60 years in the emergency department. A total of 368 study participants were enrolled by systematic random sampling between April and June 2019. An interviewer administered structured questionnaire was used to collect socio-demographic and clinical data. Patients’ medical records were also reviewed. Blood samples were collected for measurement of sodium, urea and glucose levels. Data was analysed for prevalence with statistical significance set at p<0.05. Results: A total of 368 participants were included in the final analysis. Prevalence of hyponatremia was 70.38% (259/368). The most common subtypes were mild hyponatremia (n= 100; 27.2%) and hypotonic (true) hyponatremia (n=152; 41.3%). Other classes comprised of moderate hyponatremia (n=66; 17.9%), severe hyponatremia (n= 93; 25.3%), hypertonic hyponatremia (n= 60; 16.3%) and normotonic hyponatremia (n= 47; 12.8%). The most prevalent co-morbidity was hypertension (37.0%), followed by infections (24.7%), malignancies (19.6%), Diabetes Mellitus (11.1%) and stroke (9.8%). There was however no significant association between low salt diet and hyponatremia (OR=0.31; 95% CI 0.08 to 1.15; p=0.08). Use of thiazide diuretics (OR= 4.58; 95% CI 1.48 to 14.20; p=0.008) and age group 70-79 (OR=1.92; 95% CI 1.06 to 3.50; p=0.032) were identified as independent factors associated with hyponatremia among the elderly patients. Conclusion: There is a relatively high prevalence of hyponatremia among the elderly patients at MTRH. Factors significantly associated with hyponatremia were age group 70-79, and the use of thiazide diuretics Recommendations: Routine screening, monitoring and management of hyponatremia in the elderly due to its high prevalence and associated morbidity and cautious use of thiazides in the management of hypertension in the elderly due to the high risk of developing hyponatremia.