Locus of control and breathlessness: a cross-sectional analysis of 28 730 people.

Background: Long-term pathological breathlessness is a life-limiting symptom that risks taking control of the individual's life. We aimed to evaluate how locus of control (LOC), an individual's perceived control of present and past life events, relates to breathlessness in a middle-aged general population.

Methods: A population-based, cross-sectional analysis of people aged 50-64 years was conducted in the Swedish CArdioPulmonary bioImage Study (SCAPIS). Breathlessness was measured using the modified Medical Research Council (mMRC) breathlessness scale. LOC was assessed using five-point scales related to work, life events, perceived future, treated by other people, past changes and life improvements. The LOC factors were dichotomised as having an external or internal LOC. Logistic regression was used to examine the association between external LOC and presence of moderate/severe breathlessness (mMRC ≥2). Associations between external LOC and higher breathlessness severity score (mMRC 0-4) were analysed using ordinal regression. The models were adjusted for age, sex, education level, pack-years of smoking, body mass index, lung function, depression and cardiorespiratory diseases.

Results: Of 28 730 participants (52% women), 4% experienced breathlessness. Breathlessness was related to external LOC in relation to life events (odds ratio (OR) 1.47, 95% confidence interval (CI) 1.26-1.71), future (OR 1.89, 95% CI 1.53-2.34), treated unfairly (OR 1.73, 95% CI 1.42-2.09), past changes (OR 1.50, 95% CI 1.30-1.74) and life improvements (OR 2.91, 95% CI 2.35-3.59). External LOC was associated with increased breathlessness severity.

Conclusion: External LOC is associated with experiencing worse breathlessness, and the identified LOC factors can be considered in future intervention studies aiming to reduce the suffering from breathlessness.