BACKGROUND: Frailty is associated with an increased risk of adverse health outcomes and may worsen over time. OBJECTIVES: This study aims to describe the dynamic trajectory of frailty, identify the characteristics of those who deteriorate first, and determine what deteriorates first. STUDY DESIGN AND SETTING: A primary care longitudinal population-based cohort with repeated measures at baseline and one year later. PARTICIPANTS: The cohort included all 119,952 Meuhedet members aged 65 years and over as of January 2023. PREDICTORS: Demographic factors, health indicators, and the Meuhedet Electronic Frailty Index containing 36 deficits. OUTCOMES: Worsening frailty is defined as a higher frailty level one year later in 2024 compared to 2023. A new frailty deficit is defined as a deficit appearing in 2024 that was not present in 2023. STATISTICAL ANALYSIS: The comparison of worsening percentages by demographic and clinical characteristics was tested using the chi-square test at the univariable level and logistic regression at the multivariable level. RESULTS: Overall, 13.3% of participants worsened after one year of follow-up, with 2.3% dying. Higher risk groups for worsening included females, older individuals, those belonging to the Arab sector, and those with multimorbidity. New deficits mainly included modifiable risk factors related to general health and functionality, despite chronic diseases being more frequent at baseline. CONCLUSIONS: Emphasizing intervention programs based on these health promotion issues may significantly impact disease control and slow frailty worsening.