Primary care unattachment: impact on mortality, hospitalizations and costs.

Introduction: Primary care attachment is the formal or informal affiliation with a regular primary care clinician. In countries with near-universal primary care, a physician's retirement typically results in the transition of care to another doctor. In many low- and middle-income countries, as well as the United States and Canada, this seamless transition often does not exist. A period of unattachment follows, during which the individual lacks primary care. Methods: This population-based retrospective cohort study of 12 726 325 Ontarians uses health administrative data to examine how the duration of attachment and unattachment influences mortality, healthcare costs, and hospitalizations. Results: A period of increased vulnerability was observed within the first 5 years of unattachment, associated with 85% higher odds of all-cause mortality compared with those attached for 15+ years. This association was amplified among multimorbid patients. Relative to long-term attached individuals without comorbidity, multimorbid patients exhibited approximately 5-fold higher all-cause mortality when stably attached, increasing to roughly 12-fold among those recently unattached. Cost and hospitalization outcomes exhibited similar patterns. Conclusion: These findings carry crucial policy implications, underscoring the need for strategies that promote stable attachment, particularly for individuals with multimorbidity, and better patient support following the loss of a primary care physician.