Long-term follow-up in research refers to the continued study and tracking of participants over an extended period of time, often years or even decades, after an initial study or intervention has taken place. This allows researchers to assess the long-term effects, outcomes, and impacts of the intervention or treatment, providing valuable information on the sustainability and effectiveness of the intervention. Long-term follow-up is crucial for gaining a comprehensive understanding of the long-term effects of treatments or interventions on participants' health, well-being, and outcomes.