Perception of airway obstruction in asthma: sequential daily analyses of symptoms, peak expiratory flow rate, and mood.

BACKGROUND AND OBJECTIVE: Studies have demonstrated a weak correlation between the degree of airways obstruction and the severity of asthma symptoms. Although the causes for this disparity are probably multiple, mood has been hypothesized to modulate symptoms. This investigation was designed to evaluate the effect of mood and other patient characteristics on the perception of airways obstruction.

METHODS: We compared mood variables, symptom severity, albuterol use, and peak expiratory flow rate (PEFR) measured three times daily over a 21-day period in 21 adults with moderate to severe asthma. Electronic equipment was used for data collection. Analyses included both individual patient assessments and a within-subjects, time series, pooled regression of concurrent and time-lag data.

RESULTS: After pooling 1323 observations, there was a weak concurrent relationship between symptoms and PEFR (beta = -0.17, p < 0.001). Only five patients (24%) were accurate perceivers, defined by a statistically significant relationship between symptoms and PEFR across time. Higher forced expiratory flow at 25% to 75% of capacity predicted perception accuracy (p = 0.004); active mood was marginally associated with accuracy (p = 0.06). These two variables together explained 41% of the variation in perception accuracy (p = 0.004). Mood did not independently predict symptoms, but conversely, increased symptoms predicted less pleasant mood (beta = 0.08, p < 0.001), less active mood (beta = -0.11, p < 0.001), and less active-pleasant mood (beta = 0.06, p < 0.001). PEFR did not predict mood, and only pleasant mood independently predicted higher PEFR (beta = 0.04, p < 0.05). Symptoms, but not PEFR, were concurrently associated with albuterol use (beta = 0.24, p < 0.001).

CONCLUSION: The relationship between changes in PEFR and symptoms over time was generally poor. Those patients with lower FEF25-75 values tended to be less accurate perceivers. Mood states were influenced by asthma symptoms, but the converse was not true.