Measuring symptoms in community-dwelling older adults: the psychometric properties of a brief symptom screen

Abstract

Background: With aging, the probability of experiencing multiple chronic conditions has increased, along with symptoms associated with these conditions. Symptoms form a central component of illness burden, and distress. To date, most symptom measures have focused on a particular disease population.

Objective: We aimed to develop and evaluate a simple symptom screen using data obtained from a representative sample of community-dwelling older adults.

Methods: Psychometric analyses were conducted on 10 self-reported dichotomous symptom indicators collected during in-person interviews from a sample of 1000 community-dwelling older adults. Symptoms included shortness of breath, feeling tired or fatigued, problems with balance or dizziness, perceived weakness in legs, constipation, daily pain, stiffness, poor appetite, anxiety, and anhedonia.

Results: Over one third of the individuals (37.4%) had 5 or more concurrent symptoms. Stiffness and feeling tired were the most common symptoms. Confirmatory factor analyses were performed on the 10 symptoms for single factor and bifactor (physical and affective) models of symptom reporting. Goodness-of-fit indices indicated better fit for the bifactor model (χdf=10=89.6; P<0.001), but the practical significance of the improvement in fit was negligible. Differential item functioning analyses showed some differences of relatively high magnitude in location parameters by race; however, because the differential item functioning was in different directions, the impact on the overall measure was most likely lessened.

Conclusions: Among community-dwelling older adults, a large proportion experienced multiple co-occurring symptoms. This Brief Symptom Screen can be used to quickly measure the overall symptom load in older adult populations, including those with multiple chronic conditions.

Figure 1. General Symptom Burden Confirmatory Factor Analysis Models (N=1000)

Item factor loadings and threshold parameters are parameterized in a two-parameter probit metric.

Figure 2. Scatterplot of symptom discrimination by symptom location on the symptom burden scale (N=1000)

Symptom discrimination and location (threshold) parameters are parameterized in a two-parameter probit metric. This graphic plots the magnitude of the relationship between each symptom and the underlying factor from a single-factor CFA (symptom discrimination) against the location of the symptom along the level of the symptom burden trait.