Greater continuity and lower mortality: Is there an effect in primary care?
Continuity is a core principle of general/family practice, but is declining. Past studies suggest that benefits include improved patient satisfaction, better prevention and lower hospital admissions. A recent review concluded that higher continuity in primary and/or secondary care was associated with lower mortality.
We reviewed all studies investigating associations between a quantifiable measure of continuity (informational, management or relational) of primary medical care exclusively with a measure of mortality, and reviewed any mechanisms described. We included original empirical quantitative studies of any design, published in English or French since the inception of the bibliographies searched (Medline, EMBASE, PsychINFO, and for unpublished studies Open Grey and the library catalogue of the NYAM). The data extracted were: authors; publication year; design; setting; patients included; measure of continuity and mortality; covariates in statistical models; type of statistical model, whether outcome had been transformed; continuity beta coefficient estimate (95% CI); continuity variability estimate; missing data. The assessment of bias used the 2011 version of the mixed methods appraisal tool (MMT), designed for the appraisal of randomised, non-randomised, quantitative descriptive, qualitative and mixed methods studies. We planned to conduct a meta-analysis if methods used in the included studies were sufficiently similar.
We assessed 2251 articles in abstract, 67 in full text, finally including 12. Papers came from the USA (3), Canada (3), England (2), France (1), Israel (1), South Korea (1), and the Netherlands (1). Only relational continuity was studied. Studies included: all primary care patients (3); patients aged 60 or over (5), people with diabetes (1), heart failure (1), and specific chronic conditions (4). All studies reported at least one measure of greater continuity being associated with lower mortality. However, in one US study, only one of 16 measures of continuity had a protective link with mortality, seven continuity measures derived from claims data and one from patient reports being associated with increased mortality. We will present a meta-analysis of the suitable (confounder adjusted) studies where outcomes were similar (hazard ratios), and the continuity measures continuous. Ten studies suggested a mechanism to explain the reported association between continuity and mortality; these included greater trust and knowledge and improved preventive care. No study related continuity to patient safety.
Our findings are consistent with a positive effect of continuity on mortality, although one study showed inconsistent results between different measures of continuity. The studies were all observational; potential mechanisms were not adequately investigated and reverse causation is also possible. Evidence about the association with mortality suggests that more good than harm is likely, but randomised trials are feasible and would be much more persuasive.