BackgroundMultimorbidity is increasingly recognized as a major public health challenge of modern societies. However, knowledge about the size of the population suffering from multimorbidity and the type of multimorbidity is scarce. The objective of this study was to present an overview of the prevalence of multimorbidity and comorbidity of chronic diseases in the Dutch population and to explore disease clustering and common comorbidities.MethodsWe used 7 years data (2002–2008) of a large Dutch representative network of general practices (212,902 patients). Multimorbidity was defined as having two or more out of 29 chronic diseases. The prevalence of multimorbidity was calculated for the total population and by sex and age group. For 10 prevalent diseases among patients of 55 years and older (N = 52,014) logistic regressions analyses were used to study disease clustering and descriptive analyses to explore common comorbid diseases.ResultsMultimorbidity of chronic diseases was found among 13% of the Dutch population and in 37% of those older than 55 years. Among patients over 55 years with a specific chronic disease more than two-thirds also had one or more other chronic diseases. Most disease pairs occurred more frequently than would be expected if diseases had been independent. Comorbidity was not limited to specific combinations of diseases; about 70% of those with a disease had one or more extra chronic diseases recorded which were not included in the top five of most common diseases.ConclusionMultimorbidity is common at all ages though increasing with age, with over two-thirds of those with chronic diseases and aged 55 years and older being recorded with multimorbidity. Comorbidity encompassed many different combinations of chronic diseases. Given the ageing population, multimorbidity and its consequences should be taken into account in the organization of care in order to avoid fragmented care, in medical research and healthcare policy.

Because of the heterogeneity of comprehensive care programs, it is as yet too early to draw firm conclusions regarding their effectiveness. More rigorous evaluation studies are necessary to determine what constitutes best care for the increasing number of people with multiple chronic conditions.

Despite the fact that over the years several (good-quality) studies have been performed to estimate the value of comprehensive care for multimorbid and/or frail patients, evidence for their effectiveness remains insufficient. More good-quality studies and/or studies allowing meta-analysis are needed to determine which specific target groups at what moment will benefit from comprehensive care. Moreover, evaluation studies could improve by using more appropriate outcome measures, e.g. measures that relate to patient-defined (personal) goals of care.

The outcomes of chronic care management for diabetes are generally positive, yet differ considerably across trials. The most promising results are attained in studies with limited follow-up (<1 year) and by programmes including more than two CCM components. These factors can, however, explain only part of the heterogeneity in effectiveness between studies. Other potential sources of heterogeneity should be investigated to ensure implementation of evidence-based improvements in diabetes care.

Objective. To support decision making on how to best redesign chronic care by studying the heterogeneity in effectiveness across chronic care management evaluations for heart failure. Data Sources. Reviews and primary studies that evaluated chronic care management interventions. Study Design. A systematic review including meta-regression analyses to investigate three potential sources of heterogeneity in effectiveness: study quality, length of followup, and number of chronic care model components. Principal Findings. Our meta-analysis showed that chronic care management reduces mortality by a mean of 18 percent (95 percent CI: 0.72-0.94) and hospitalization by a mean of 18 percent (95 percent CI: 0.76-0.93) and improves quality of life by 7.14 points (95 percent CI: À9.55 to À4.72) on the Minnesota Living with Heart Failure questionnaire. We could not explain the considerable differences in hospitalization and quality of life across the studies. Conclusion. Chronic care management significantly reduces mortality. Positive effects on hospitalization and quality of life were shown, however, with substantial heterogeneity in effectiveness. This heterogeneity is not explained by study quality, length of follow-up, or the number of chronic care model components. More attention to the development and implementation of chronic care management is needed to support informed decision making on how to best redesign chronic care.