Treatment burden in complex versus simple multimorbidity: nationwide cross-sectional study in Japan

The concept of "complex multimorbidity", defined as the coexistence of three or more long-term conditions affecting at least three different body systems, has recently emerged in medical literature. However, it remains unclear whether this concept effectively identifies patients with greater complexity of care needs.

We aimed to evaluate how treatment burden differs between complex and simple multimorbidity.

We conducted a nationwide cross-sectional survey of the Japanese adult population. The primary outcome measure was high treatment burden, as assessed by the Japanese version of the Multimorbidity Treatment Burden Questionnaire (MTBQ). We used a multivariable modified Poisson regression analysis to adjust for possible confounders.

Of the 1341 participants, 384 (28.6%) had multimorbidity, and 130 (9.7%) had complex multimorbidity. The presence of complex multimorbidity tended to increase with age. After adjusting for possible confounders, complex multimorbidity was associated with an increase in high treatment burden, compared with simple multimorbidity (adjusted prevalence ratio = 1.47, 95% CI: 1.14-1.90).

Patients with complex multimorbidity experienced a higher treatment burden than those with simple multimorbidity in a nationally representative sample of Japanese adults. These findings support the conceptual distinction of complex multimorbidity for identifying patients with complex healthcare needs. Recognizing these subgroups and implementing strategies to reduce treatment burden may contribute to improved health outcomes for patients with multimorbidity.