Quadriceps muscle strength is a discriminant predictor of dependence in daily activities in nursing home residents

OBJECTIVE: This study aimed to explore the relationship between dependence in Activities of Daily Living and muscle strength, muscle morphology and physical function in older nursing home residents, taking possible confounders into consideration. METHODS: A total of 30 nursing home residents (age, 85.6±7.1 years) were included in this observational cross-sectional study. Performance of basic Activities of Daily Living (ADL) was assessed with the Resident Assessment Instrument and categorized as either independent or dependent. Isometric grip, quadriceps and elbow-flexor strength were determined by hand-dynamometry, muscle thickness and echo intensity by B-mode ultrasonography, a sit-to-stand task by using a stop watch and physical activity by the German-Physical-Activity Questionnaire. Degree of frailty was evaluated according to Fried’s frailty criteria, whereas cognition, depression, incontinence, pain and falls were part of the Resident Assessment Instrument. RESULTS: Dependence in Activities of Daily Living was negatively correlated with physical activity (r(s) = -0.44, p = .015), handgrip (r(s) = -0.38, p = .038), elbow-flexor (r(s) = -0.42, p = .032) and quadriceps strength (r(s) = -0.67, p < .001), analysed by Spearman’s correlation. Chronic diseases (r(s) = -0.41, p = .027) and incontinence (r(s) = -0.39, p = .037) were positively correlated with ADL while the other variables were not related. Only quadriceps strength remained significant with logistic regression (Wald(1) = 4.7, p = .03), when chronic diseases, quadriceps and handgrip strength were considered (R(2) .79). 11 kg was the best fitting value in this sample to predict performance in Activities of Daily Living, evaluated with Receiver-Operating Characteristic analysis, with a sensitivity of 100% and a specificity of 79%. CONCLUSION AND IMPLICATION: Quadriceps strength had a positive independent relationship with performance in ADL in the nursing home residents studied. Although a large prospective study is needed to verify the results, maintaining quadriceps strength above 11 kg may be helpful in retaining independence in this cohort.