Distinct Asthma Phenotypes Among Older Adults with Asthma

Abstract

Background: Older adults have high rates of asthma morbidity and mortality. Asthma is now recognized as a heterogeneous disease, yet the distinct phenotypes among older adults are unknown.

Objective: The objective of this study was to identify asthma phenotypes in a diverse population of elderly patients with asthma.

Methods: Using cluster analysis, 180 older adults with persistent asthma were analyzed. Subjects completed detailed questionnaires, skin prick testing, and spirometry with reversibility. Twenty-four core variables were analyzed.

Results: Four groups were identified. Subjects in cluster 1 (n = 69) typically had asthma diagnosed after the age of 40 and the shortest duration of asthma. Cluster 2 (n = 40) had the mildest asthma defined by spirometry, Asthma Control test (ACT), and Asthma Quality of Life Questionnaire (AQLQ). They also had the lowest body mass index (BMI), lowest depression score, and least number of comorbidities. Cluster 3 (n = 46) had the longest duration of asthma (56 years) and the highest atopic skin test sensitization (74%). Cluster 4 (n = 25) had the most severe asthma, with extremely low FEV₁% predicted (37.8%), lowest ACT, and lowest AQLQ scores. They were more likely to be black and had the highest comorbidities. Using BMI, posttreatment FEV₁% predicted, and duration of asthma, 95.6% of subjects were able to be correctly classified.

Conclusions: In older adults with asthma, distinct phenotypes vary on key features that are more pronounced among the elderly, including comorbidities, fixed airway obstruction, and duration of asthma ≥40 years. Further work is required to determine the clinical and therapeutic implications for different asthma phenotypes in older adults.

Keywords: Asthma; Asthma classification; Atopic sensitization; Cluster analysis; Fixed airway obstruction; Older adults; Phenotypes.