Heat-related symptom worsening, cooling constraints, and care disruption among older cardiology outpatients: a convergent mixed-methods study

Background Hot weather is an established cardiovascular hazard, but patient-level evidence on how clinical vulnerability, cooling constraints and barriers to care interact in older cardiology outpatients remains limited. Methods We conducted a convergent mixed-methods study in the cardiology outpatient clinic of a tertiary university hospital in Zonguldak, Türkiye, from June to August 2026. A total of 680 consecutively recruited patients aged ≥ 65 years completed a structured interviewer-administered survey covering heat-related symptoms, housing and cooling capacity, health-care access and frailty assessed using the Clinical Frailty Scale (CFS). The primary outcome was self-reported heat-related worsening of cardiovascular symptoms; secondary outcomes included care delay and marked impact on daily life. Multivariable logistic regression was used, and a pragmatic seven-domain heat-vulnerability index was explored. Twenty purposively sampled participants underwent semi-structured interviews, analysed thematically and integrated with the quantitative findings. Results Mean age was 71.3 ± 5.3 years and 48.1% were women. Inadequate effective cooling was reported by 82.4%, at least two heat-related symptoms by 75.9%, and heat-related care delay by 30.9%. Among participants giving a definite response, 52.1% reported symptom worsening, independently associated with heart failure (adjusted odds ratio [aOR] 1.86, 95% CI 1.18–2.95), prolonged hot indoor exposure (aOR 1.82, 1.19–2.81), summer transport difficulty (aOR 1.65, 1.08–2.53) and greater frailty (aOR per CFS point 1.30, 1.09–1.55). Care delay was associated with limited or absent daytime support (aOR 2.99, 2.05–4.35), transport difficulty (aOR 2.59, 1.67–4.00), living alone (aOR 2.45, 1.62–3.70) and insufficient income (aOR 2.02, 1.34–3.03). Symptom worsening, care delay and daily-life impact increased across vulnerability categories. Interviews showed that effective cooling, access to care and social support depended on their practical usability rather than nominal availability. Conclusions Heat-related burden in older cardiology outpatients extends beyond acute events to symptoms, daily functioning and continuity of care, consistent with a multidimensional pattern of clinical, environmental and social vulnerability. Frailty, effective cooling, transport and reliable support may be relevant domains for brief heat-health discussions in outpatient cardiovascular care. Clinical trial number Not applicable.