Older adults with a higher frailty index tend to have electrolyte imbalances

Objectives: Frailty is a state of increased vulnerability to poor resolution of homeostasis after a stressor. We hypothesized that frail older adults would tend to have electrolyte imbalances because they should have many stressors together with fragile physiological systems. In this study, we aimed to determine whether older adults with higher Frailty Index scores have electrolyte imbalances and to establish which domains of the Frailty Index are correlated with electrolyte imbalances. Design: A cross-sectional study. Setting and participants: A total of 4204 older adults aged 70 years or over who visited the Japanese National Center for Geriatrics and Gerontology. Methods: We calculated the 50-item Frailty Index with the following domains: comorbidities, cognitive function and mood, basic and instrumental activities of daily living, physical function, nutrition, and fall risks from physical weakness and comorbidities. Participants were categorized into four groups: a non-frail group (Frailty Index ≤0.2), mildly frail group (0.20 < Frailty Index ≤0.3), moderately frail group (0.3 < Frailty Index ≤0.4), and severely frail group (0.4 < Frailty Index). Their serum sodium, potassium, calcium, and phosphorus concentrations were measured. A multiple regression model was used to explore the relationship of electrolyte imbalances with the Frailty Index and to determine which frailty domains are correlated with electrolyte imbalances. Results: Compared with the non-frail group, the mildly and moderately frail groups tended to have hypernatremia and hypophosphatemia, whereas the severely frail group tended to have dysnatremia, hypokalemia, and hypophosphatemia. The estimated odds ratios increased by 15%–52% for each electrolyte imbalance as the Frailty Index increased by 0.1. The Frailty Index domains of cognitive function, activities of daily living, and nutrition were correlated with more than three kinds of electrolyte imbalances, the domains of physical function and fall risks from physical weakness were correlated with three kinds of electrolyte imbalances, and the domains of comorbidities and fall risks from comorbidities were correlated with two kinds of electrolyte imbalances. Conclusions: Older adults with higher Frailty Index scores tend to have electrolyte imbalances.