Increased attention has been given to multimorbidity. This phenomenon often has been explored through associations between diseases based on the frequency of combinations of diagnoses. A more patient-focused strategy, together with a trajectory of the multimorbidity situation, has recently attracted increased interest. Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a state that per se includes multimorbidity and is preceded by numerous ambiguous diagnoses. A history of infectious disease is considered the most common denominator and pathophysiological base of ME/CFS, even though no biomarker of such infection has been found. Exploring changing patterns of multimorbidity might contribute to the knowledge about the unknown pathophysiology of this disease.

Methods and materials

This was a retrospective register-based cohort study of 549 patients from 2015–2020 in Region Stockholm, Sweden. We processed the number and type of diagnoses during each year according to the Adjusted Clinical Groups© case-mix system from Johns Hopkins University. The images were visualized with Excel and “Gapminder” software.

Results

Fifty percent of all patients had more than eight diagnoses—up to 32 diagnoses per year—during the last twelve months of the study period. The most frequent diagnosis clusters were “General Signs and Symptoms”, “Musculoskeletal”, “Psychosocial” and “Neurologic”. The cluster “Infections” was found as number fifteen in order. The number of patients with psychiatric or psychosomatic disorders was lower after the registration of ME/CFS diagnoses.

Discussion and conclusion

This study illustrates the complexity of the pattern of multimorbidity over time, depicting overlapping diagnoses. Analyses of trajectories of different patterns of multimorbidity might pave the way for a broader understanding of triggers for more complex health conditions, as seen in the case of ME/CFS. The traditional view that ME/CFS is the result of an infectious disease was not confirmed in our cohort. The drive toward patient-oriented analyses may lead to findings of subcategories of patients with similar patterns of multimorbidity over time.