Epidemiology and impact of multimorbidity in primary care: a retrospective cohort study.

BACKGROUND In developed countries, primary health care increasingly involves the care of patients with multiple chronic conditions, referred to as multimorbidity. AIM To describe the epidemiology of multimorbidity and relationships between multimorbidity and primary care consultation rates and continuity of care. DESIGN OF STUDY Retrospective cohort study. SETTING Random sample of 99 997 people aged 18 years or over registered with 182 general practices in England contributing data to the General Practice Research Database. METHOD Multimorbidity was defined using two approaches: people with multiple chronic conditions included in the Quality and Outcomes Framework, and people identified using the Johns Hopkins University Adjusted Clinical Groups (ACG®) Case-Mix System. The determinants of multimorbidity (age, sex, area deprivation) and relationships with consultation rate and continuity of care were examined using regression models. RESULTS Sixteen per cent of patients had more than one chronic condition included in the Quality and Outcomes Framework, but these people accounted for 32% of all consultations. Using the wider ACG list of conditions, 58% of people had multimorbidity and they accounted for 78% of consultations. Multimorbidity was strongly related to age and deprivation. People with multimorbidity had higher consultation rates and less continuity of care compared with people without multimorbidity. CONCLUSION Multimorbidity is common in the population and most consultations in primary care involve people with multimorbidity. These people are less likely to receive continuity of care, although they may be more likely to gain from it.