Box 1.

Suggested mechanisms by which any type of continuity might influence mortality

Study	Suggested mechanisms
*Selected populations*
Wolinsky et al (2010)¹⁹	Continuity is defined as ‘”an ongoing relationship with a particular [primary care] physician in the outpatient setting with sufficient frequency for that physician to assume primary responsibility for both the patient’s basic health care needs and her overall disease and care management” […] Continuity is expected to result in “improved doctor–patient relationships, enhanced physician knowledge of the patient, greater rapport and disclosure, increased compliance, reduced hospitalization rates, increased patient and physician satisfaction, reductions in disability levels, costs, and missed appointments, and improved problem recognition and management”.’¹⁹
Worrall and Knight (2011)²⁰	None.
Leleu and Minvielle (2013)²¹	Consultations with the same primary care practitioner can lead to a better understanding of patients’ health needs, better management, and builds up a relationship of trust.
McAlister et al (2013)²²	None
Bentler et al (2014)²³	‘Longitudinal continuity … [provides] a chance for interpersonal continuity to develop … [which] means that knowledge, trust, and respect have developed … over time allowing for better interaction and communication. Within interpersonal continuity, there are both instrumental (provider knowledge about the patient) and affective (mode of provider behaviour toward the patient) [continuity] … that contribute to a good patient-provider relationship. […] establishing a caring, trusting bond as part of the patient-provider relationship helps both the patient and provider understand when outpatient and home care can substitute for hospitalization.’²³
Nelson et al (2014)²⁴	None. Continuity regarded as a feature of the patient-centred medical home.
Shin et al (2014)²⁵	‘A physician who attends the same patient regularly is likely to have better knowledge of him or her, to recognize problems earlier, and to provide higher quality of care. Furthermore, patients who have continuity with the same physician are more likely to adopt better self-management behaviours and to increase adherence to medication recommendations, probably because of greater trust and to have higher satisfaction with their physicians.’²⁵
Lustman et al (2016)²⁶	‘It is not possible to say if higher interpersonal continuity is causal in reducing mortality, this result is as likely due to very ill patients changing doctors or going to the most readily available doctor …’²⁶
Maarsingh et al (2016)²⁷	‘The assumed benefits of continuity of care include a better patient–provider relationship, increased patient satisfaction, improved uptake of preventive care, enhanced adherence to treatment, more accessible health care, and reduced healthcare use and costs. Especially vulnerable patients, such as older patients, are considered to benefit from continuity of care, as they are likely to have multiple chronic conditions.’ ²⁷
McAlister et al (2016)²⁸	‘It seems reasonable to hypothesize that healthcare providers (physicians or nurses/pharmacists) who have a longer-term relationship with a patient are likely to have a better sense of that patient’s unique situation and the numerous nonmedical issues that influence hospitalization risk.’ ²⁸
Geroldinger et al (2018)³¹	Patients who benefit from multidisciplinary care, which is reflected by low total continuity, may have a smaller risk of mortality. Measures of continuity are sensitive to the types of medical disciplines taken into account.

*Entire primary care population*
Levene et al (2012)²⁹	‘Starfield et al identified mechanisms potentially accounting for the beneficial impact of primary care on population health, including greater access to needed services, better quality of care, greater focus on prevention, earlier disease management, and the cumulative effect, with a holistic focus, of greater continuity and comprehensiveness.’ ²⁹
Honeyford et al (2013)³⁰	In a referenced conceptual model, the authors suggest that quality primary health care (access with sustained patient relationships and/or interventions) can modify the relationship between risk factors and probability of death.