Table 1_The trigger-timing framework for long COVID: using symptom triggers and temporal patterns to guide mechanistic stratification and treatment planning.docx

The timing of symptom worsening after these stressors provides additional information because immediate, short-delay, same-day, delayed, cumulative, and circadian responses may reflect different response kinetics. The framework integrates four core clinical dimensions: the trigger that provokes symptom worsening, the timing of symptom onset, the symptom pattern that emerges, and the relief or recovery pattern that follows.

Immediate worsening with standing, heat exposure, meals, or upright exertion, especially when relieved by lying down, supports an autonomic or circulatory pattern. Delayed worsening after physical or cognitive exertion supports impaired recovery physiology and post-exertional malaise. Meal-related symptoms may suggest autonomic, metabolic, gastrointestinal, or mast cell-related physiology depending on timing and accompanying symptoms.

Circadian or persistent patterns may suggest neuroendocrine, sleep-related, autonomic, or inflammatory rhythm instability. This framework is intended as a companion operational framework to a mechanism-anchored network model of Long COVID. It may help guide targeted diagnostic evaluation, treatment prioritization, sequencing decisions, longitudinal tracking, and research cohort enrichment.

The model remains conceptual and requires prospective validation to determine whether trigger-timing patterns correlate with objective physiological measures, predict differential treatment response, and improve outcomes compared with symptom-based stratification alone.</p>