Temperature extremes and autoimmune diseases.

Temperature extremes linked to climate change are becoming more frequent and more intense. This has significant implications for human health, including conditions driven by immune dysregulation. There is growing evidence that external thermal stress, particularly heat, may influence both the development and clinical course of several autoimmune conditions. Heat and cold can alter immune cell function through effects on cell signalling, cytokine production, barrier integrity and stress response within tissues. These mechanisms provide a strong biological basis for the observed associations between seasonal or regional temperature patterns and rates of autoimmune disease onset, symptoms, or flare frequency. Temperature extremes present considerable specific health risk to people with autoimmune disease with examples including heat waves worsening fatigue and neurological symptoms in people with multiple sclerosis and cold spells triggering blood vessel constriction and extremity tissue necrosis in systemic sclerosis. As climate instability increases, people with autoimmune disease will face higher clinical risk, due to disease-related factors and increased risks from cardiovascular related morbidity and mortality and concomitant demographic and socio-economic factors. This highlights the need for climate-aware healthcare, patient education, and research that addresses the interface of environmental factors with immune and clinical outcomes.