Effects of household and neighbourhood attributes on four definitions of multimorbidity: a comparative multilevel analysis of linked clinical and census data of Wales.

To compare the influence of household and neighbourhood factors on the risk of four definitions of multimorbidity (multimorbidity), namely (1) patients with two or more long-term conditions (long-term conditions) (2+multimorbidity), (2) patients with three or more long-term conditions and (3) patients with three or more long-term conditions from three or more International Classification of Diseases (10th Revision) body systems and (4) 2+multimorbidity patients with at least one mental long-term conditions and one physical long-term conditions.