title: Multimorbidity in primary care: a systematic review of prospective cohort studies.
abstract: BACKGROUND
  Primary care increasingly deals with patients with multimorbidity, but relevant evidence-based interventions are scarce. Knowledge about multimorbidity over time is required to inform the development of effective interventions.
  
  
  OBJECTIVE
  This review  identifies prospective cohort studies of multimorbidity in primary care to determine: their nature, scope and key findings; the methodologies used; and gaps in knowledge.
  
  
  METHODS
  Systematic review.
  
  
  METHODS
  Studies were identified by searching electronic  databases, reviewing citations, and writing to authors. Searches were limited to adult populations with no restrictions on publication date or language. In total, 996 articles were identified and screened.
  
  
  RESULTS
  Of the 996 articles, six detailing five completed prospective  cohort studies were selected as appropriate. Three of the studies were undertaken in the US and two in The Netherlands; none was nationally representative. The main focus of the studies was: healthcare utilisation and/or costs (n = 3); patients' physical functioning (n = 1);  and risk factors for developing multimorbidity (n = 1). The conditions that were included varied widely. The findings of these studies showed that multimorbidity increased healthcare costs (n = 2), inpatient admission (n = 1), death rates (n = 1), and service use  (n = 3), and reduced physical functioning (n = 1). One study identified psychosocial risk factors for multimorbidity. No study used random sampling, sample sizes were relatively small (414-3745 patients at baseline), and study duration was relatively short (1-4 years).  No study focused on prevalence, treatment use, patient safety, service models, cultural or socioeconomic factors, and patient experience, and no study collected qualitative data.
  
  
  CONCLUSIONS
  Few longitudinal studies based in primary care have investigated multimorbidity.  Further large, long-term prospective studies are required to inform healthcare commissioning, planning, and delivery.
authors.affiliation: Alliance for Self Care Research, University of Stirling, Stirling.
authors.forename: Emma F
authors.initials: EF
authors.lastname: France
authors.forename: Sally
authors.initials: S
authors.lastname: Wyke
authors.forename: Jane M
authors.initials: JM
authors.lastname: Gunn
authors.forename: Frances S
authors.initials: FS
authors.lastname: Mair
authors.forename: Gary
authors.initials: G
authors.lastname: McLean
authors.forename: Stewart W
authors.initials: SW
authors.lastname: Mercer
mesh_terms: D000328:Adult; D002908:Chronic Disease / Q000453:epidemiology* / Q000628:therapy; D015897:Comorbidity; D006801:Humans; D011320:Primary Health Care / Q000706:statistics & numerical data*; D011446:Prospective Studies