Abstract
BACKGROUND: It is unclear whether climate may play a role in the association between hyponatremia on admission and increased mortality risk among hip fracture patients following a hip fracture repair surgery. We aimed (1) to explore if there is any combined effect of seasonality and hyponatremia on the occurrence of hip fractures among older adults and (2) to explore the effect of hyponatremia on admission on mortality rate at latest follow-up among hip fracture patients following a hip fracture repair surgery in the context of the subtropical climate of Israel. METHODS: We conducted a retrospective cohort study of older patients who underwent a surgery for hip fracture repair in a major 495-bed hospital located in northern-central Israel in 2017-2020. Patients were divided into two groups: hyponatremic (n = 107) and normonatremic (n = 757) patients. Characteristics of the two groups were compared, as well as their survival probability. RESULTS: Hyponatremic patients were most frequently hospitalized during winter season. Such seasonal variation was observed only among hyponatremic patients. Moreover, patients who were hospitalized during winter season were more likely to be hyponatremic on admission. Hyponatremia on admission was found as a significant independent predictor of mortality rate at latest follow-up (adjusted hazard ratio = 0.377 [0.26-0.52]), when compared to normonatremia. CONCLUSION: There is a combined effect of seasonality and hyponatremia on the occurrence of hip fractures among older adults, with hyponatremic patients being at a higher risk of sustaining a hip fracture during winter season than during other seasons. In addition, the association between hyponatremia on admission and mortality rate at latest follow-up among hip fracture patients has been confirmed.