we designed this retrospective cohort study to determine if pcps are more likely than covering providers to intensify medications , provide lifestyle counseling , and have shorter intervals to the next encounter for patients with diabetes and elevated a1c , ldl , or blood pressure ( bp ) . adults with diabetes treated at primary care practices affiliated with brigham and women s ( bwh ) and massachusetts general ( mgh ) hospitals for at least 2 years between 1 january 2000 and 1 january 2010 were studied . all of the practices in the study used longitudinal medical record , an internally developed office of the national coordinator 's authorized testing and certification body certified electronic medical record ( emr ) where all patient care documentation , including problem lists , electronic prescribing , and provider notes , was recorded . patients were included in the study if they were at least 18 years old , had a documented diagnosis of diabetes or a1c 7.0% , and at least one instance of a1c , bp , or ldl above treatment target . patients with missing zip codes were excluded to enable adjustment for median household income by zip code . we used treatment goals of < 7.0% for a1c , < 100 mg / dl for ldl , and < 140/90 mmhg for bp . this study was approved by the partners healthcare system institutional review board , and the requirement for written informed consent was waived . an encounter with a health care provider in a primary care practice served as the unit of analysis . an uncontrolled period started on the day when a1c , bp , or ldl was first noted above the treatment target ( 27 ) . the period ended on the first subsequent date when all measures fell below the target . encounters that fell within the uncontrolled period were included in the analysis , whether or not measurements were taken on that date . bp measurements were only included in the encounter analysis if they were measured on the same date as the encounter . if a1c and ldl measurements were unavailable on the encounter date , the most recent was carried forward if the measurement was within 6 months of the encounter date . transient elevations were defined as isolated elevated measurements that subsequently normalized without any medication intensification and were excluded from the analysis . periods without any medication information available in the emr were excluded to enable inclusion of insulin treatment as a confounder variable in the analysis . periods that contained multiple encounters with an endocrinologist were excluded to focus the analysis on the primary care setting where , nationwide , most of diabetes care takes place . hyperglycemic and hyperlipidemic periods in which rates of a1c and ldl change , respectively , were greater than three standard deviations from the mean were excluded to eliminate likely measurement errors . finally , encounters with a time to the next encounter exceeding 1 year were excluded to ensure continuous receipt of care at study practices . a pcp was defined as the pcp with whom the patient had the majority of continuous encounters over a given interval and could change in the course of an uncontrolled period . a covering physician was any other physician in a primary care setting who treated a patient . these physicians were usually other pcps in the same practice ( similarly qualified with respect to specialty and board certification ) who were assigned to urgent care or covering duty on a particular day . we identified face - to - face encounters based on availability of appropriate billing codes ; all notes without corresponding billing codes were considered remote encounters . acute encounters were defined by icd-9 diagnosis codes for an acute complaint ( e.g. , acute pain and/or infection ) as previously described ( 29 ) . documentation of lifestyle counseling ( diet , exercise , or weight loss ) was computationally abstracted from the notes , including direct ( eg , weight has gone up  ) instances of lifestyle counseling , as previously described ( 27,30 ) . we inferred lifestyle counseling if the subject was referred to in a way that indicated it was likely discussed with the patient ( eg , not simply weight recorded in the vital signs section ) . when compared with human double - entry , the software had a sensitivity of between 91 and 97% and a specificity of between 88 and 94% . weight loss counseling was only considered for encounters when a patient had a bmi 30 kg / m . none of the practices studied during the study period had a program that encouraged a particular type of lifestyle counseling or monitored lifestyle counseling delivered by providers . medication intensification was defined as initiation of a new medication or an increase in the dose of an existing medication ( 29 ) . demographic information , weight , height , bp measurements , and medication and laboratory data were obtained from the emr at partners healthcare , an integrated health care delivery network in eastern massachusetts that includes bwh and mgh . summary statistics were constructed by using frequencies and proportions for categorical data and using means , standard deviations , medians , and ranges for continuous variables . the marginal cox proportional hazards model for clustered data ( 31 ) was used to estimate the association between provider type and time to next encounter , and logistic regression models were used to calculate the odds of medication intensification and lifestyle counseling for different provider types . all models were adjusted for demographic confounders ( age , sex , race , primary language , health insurance , and median income by zip code ) , as well as the patient s charlson comorbidity index ( cci ) ( 32 ) , treatment with insulin as a marker of severity of disease , presence of obesity , diagnosis codes for metastatic cancer within 1 year before the encounter date ; measurements of a1c , systolic and diastolic bp , and ldl , face - to - face versus remote encounters , acute complaints , hospitalization before the next encounter ( time to next encounter analysis only ) , and an interaction term between acute status and provider type . two - sided p values were obtained using type iii test and were adjusted for multiple hypothesis testing using the simes - hochberg method ( 33,34 ) . all analyses were performed with sas 9.3 software ( sas institute inc . , cary , nc ) . we designed this retrospective cohort study to determine if pcps are more likely than covering providers to intensify medications , provide lifestyle counseling , and have shorter intervals to the next encounter for patients with diabetes and elevated a1c , ldl , or blood pressure ( bp ) . adults with diabetes treated at primary care practices affiliated with brigham and women s ( bwh ) and massachusetts general ( mgh ) hospitals for at least 2 years between 1 january 2000 and 1 january 2010 were studied . all of the practices in the study used longitudinal medical record , an internally developed office of the national coordinator 's authorized testing and certification body  certified electronic medical record ( emr ) where all patient care documentation , including problem lists , electronic prescribing , and provider notes , was recorded . patients were included in the study if they were at least 18 years old , had a documented diagnosis of diabetes or a1c 7.0% , and at least one instance of a1c , bp , or ldl above treatment target . patients with missing zip codes were excluded to enable adjustment for median household income by zip code . we used treatment goals of < 7.0% for a1c , < 100 mg / dl for ldl , and < 140/90 mmhg for bp . this study was approved by the partners healthcare system institutional review board , and the requirement for written informed consent was waived . an encounter with a health care provider in a primary care practice served as the unit of analysis . an uncontrolled period started on the day when a1c , bp , or ldl was first noted above the treatment target ( 27 ) . the period ended on the first subsequent date when all measures fell below the target . encounters that fell within the uncontrolled period were included in the analysis , whether or not measurements were taken on that date . bp measurements were only included in the encounter analysis if they were measured on the same date as the encounter . if a1c and ldl measurements were unavailable on the encounter date , the most recent was carried forward if the measurement was within 6 months of the encounter date . transient elevations were defined as isolated elevated measurements that subsequently normalized without any medication intensification and were excluded from the analysis . periods without any medication information available in the emr were excluded to enable inclusion of insulin treatment as a confounder variable in the analysis . periods that contained multiple encounters with an endocrinologist were excluded to focus the analysis on the primary care setting where , nationwide , most of diabetes care takes place . hyperglycemic and hyperlipidemic periods in which rates of a1c and ldl change , respectively , were greater than three standard deviations from the mean were excluded to eliminate likely measurement errors . finally , encounters with a time to the next encounter exceeding 1 year were excluded to ensure continuous receipt of care at study practices . a pcp was defined as the pcp with whom the patient had the majority of continuous encounters over a given interval and could change in the course of an uncontrolled period . a covering physician was any other physician in a primary care setting who treated a patient . these physicians were usually other pcps in the same practice ( similarly qualified with respect to specialty and board certification ) who were assigned to urgent care or covering duty on a particular day . we identified face - to - face encounters based on availability of appropriate billing codes ; all notes without corresponding billing codes were considered remote encounters . acute encounters were defined by icd-9 diagnosis codes for an acute complaint ( e.g. , acute pain and/or infection ) as previously described ( 29 ) . documentation of lifestyle counseling ( diet , exercise , or weight loss ) was computationally abstracted from the notes , including direct ( eg ,  strongly encouraged more walking  ) and inferred ( eg ,  weight has gone up  ) instances of lifestyle counseling , as previously described ( 27,30 ) . we inferred lifestyle counseling if the subject was referred to in a way that indicated it was likely discussed with the patient ( eg , not simply weight recorded in the vital signs section ) . when compared with human double - entry , the software had a sensitivity of between 91 and 97% and a specificity of between 88 and 94% . weight loss counseling was only considered for encounters when a patient had a bmi 30 kg / m . none of the practices studied during the study period had a program that encouraged a particular type of lifestyle counseling or monitored lifestyle counseling delivered by providers . medication intensification was defined as initiation of a new medication or an increase in the dose of an existing medication ( 29 ) . demographic information , weight , height , bp measurements , and medication and laboratory data were obtained from the emr at partners healthcare , an integrated health care delivery network in eastern massachusetts that includes bwh and mgh . summary statistics were constructed by using frequencies and proportions for categorical data and using means , standard deviations , medians , and ranges for continuous variables . the marginal cox proportional hazards model for clustered data ( 31 ) was used to estimate the association between provider type and time to next encounter , and logistic regression models were used to calculate the odds of medication intensification and lifestyle counseling for different provider types . all models were adjusted for demographic confounders ( age , sex , race , primary language , health insurance , and median income by zip code ) , as well as the patient s charlson comorbidity index ( cci ) ( 32 ) , treatment with insulin as a marker of severity of disease , presence of obesity , diagnosis codes for metastatic cancer within 1 year before the encounter date ; measurements of a1c , systolic and diastolic bp , and ldl , face - to - face versus remote encounters , acute complaints , hospitalization before the next encounter ( time to next encounter analysis only ) , and an interaction term between acute status and provider type . two - sided p values were obtained using type iii test and were adjusted for multiple hypothesis testing using the simes - hochberg method ( 33,34 ) . all analyses were performed with sas 9.3 software ( sas institute inc . , cary , nc ) . we identified 33,559 adults with diabetes who experienced at least one hyperglycemic , hypertensive , or hyperlipidemic period and were regularly seen in primary care practices associated with bwh or mgh ( fig . patients regularly treated by endocrinologists , without medication records , only transient elevations in a1c , bp , and ldl , likely a1c or ldl measurement errors , and missing demographic information , the remaining 27,225 unique individuals with 584,587 primary care encounters were included in the study . flow chart shows selection of study patients . study patients did not have at least one measure under control over a mean of 78% of total follow - up time ( table 1 ) . during the study period , patients mean maximum a1c was 8.7% , bp was 157/90 mmhg , and ldl was 131 mg / dl . the percentage of patients with measurements available during the follow - up period ranged from 92.9% of the time for a1c to 99.9% of the time for bp . patient characteristics during uncontrolled periods , 83% of the encounters ( table 2 ) were with pcps , 13% were with covering physicians , and 5% were with midlevel providers . face - to - face visits constituted 49% and acute visits 19% of total encounters . pcp encounters constituted 8485% of nonacute and remote encounters but only 77% of acute encounters . covering physicians , however , had a higher proportion ( 19% ) of acute encounters and 1012% of nonacute and remote encounters . midlevel providers consistently had 45% of acute , nonacute , and remote encounters . during all encounters , medication intensification occurred at 10% and lifestyle counseling occurred at 40% of encounters , whereas the mean time to the next encounter was 1.6 months . mean times since last a1c and ldl measurements were 9 and 10 weeks , respectively . providers had access to up - to - date a1c , bp , and ldl measures at 64.0 , 56.4 , and 53.5% of encounters , respectively . encounter characteristics in a multivariable logistic regression model that controlled for patient demographics , cci , obesity , a1c , bp , and ldl measurements , metastatic cancer diagnosis , insulin status , and an interaction term between acute encounter status and provider type , the odds of medication intensification during nonacute encounters were 49% ( p < 0.0001 ) and 26% ( p < 0.0001 ) higher for pcps than for covering physicians and midlevel providers , respectively ( table 3 ) . odds of lifestyle counseling during nonacute encounters were 91% ( p < 0.0001 ) higher for pcps than covering physicians and 21% ( p = 0.0015 ) higher than midlevel providers . during acute encounters , covering physicians were less likely to intensify medications by a further 52% ( p < 0.0001 ) , whereas midlevel providers were less likely to provide lifestyle counseling by a further 41% ( p < 0.0001 ) . encounter - level analysis estimates , comparing pcps with other physicians and midlevel providers in multivariable analysis in a multivariable cox proportional hazards model that adjusted for demographics , cci , insulin status , obesity , metastatic cancer diagnosis , measurements of a1c , systolic and diastolic bp , and ldl , indicators for face - to - face and acute visits , hospitalization before the next encounter , and an interaction term between acute status and provider type , the hazard ratios for the time to the next encounter after a visit without acute complaints were 1.11 for covering physicians and 1.19 for midlevel providers ( p < 0.0001 for both ) compared with pcps . in this large retrospective study , we have demonstrated that pcps were significantly more likely than other providers in the primary care setting to provide lifestyle counseling and medication intensification for patients with uncontrolled diabetes . this association was even stronger during visits in which the patient had an acute complaint . these results suggest that increased frequency of lifestyle counseling and medication intensification may be the mechanisms that underlie better outcomes seen in patients who have higher continuity of care . several other explanations for the effect of continuity of care have been proposed : increased time spent with one physician improved the patient s trust of his or her physician ( 4 ) , enhanced communication between patient and physician , and increased the physician s knowledge of the patient ( 10 ) , but the evidence for their direct effect on patient outcomes is limited . our study , however , describes mechanisms that have been directly linked to a1c , bp , and ldl control ( 2528,35,36 ) . it is likely that multiple mechanisms contribute to the effects of better disease outcomes and that the importance of provider type may vary by mechanism . many studies have shown that midlevel providers can be more effective than pcps in treatment of chronic diseases such as diabetes and hypertension ( 3740 ) , particularly with respect to medication intensification ( 41 ) . the major difference between our study and these clinical trials is that the trials usually required midlevel providers to follow a structured algorithm , whereas midlevel providers in the practices we studied did not follow any particular algorithm . this current finding should be considered when designing new practice models , such as patient - centered medical homes . although pcps are more effective than midlevel providers and covering physicians in providing lifestyle counseling and intensifying medication , a patient may be seen more frequently in practices with other providers available . this is corroborated by the shorter time to follow - up visits after encounters with covering physicians and midlevel providers found in our study . therefore , practices with midlevel providers may provide more cost - efficient care because there are more opportunities for medication intensification and lifestyle counseling at a lower cost , even if they are not used as frequently . midlevel providers could , therefore , be especially helpful in situations in which pcp resources are constrained , as they are almost universally across the country ( 4244 ) . if patients must be seen by a covering provider , better documentation of the pcp 's treatment plan in the medical records may facilitate their decision making and lower the threshold for intervention . finally , structured algorithms for treatment of chronic disease may be helpful in optimizing the care delivered by midlevel providers . lack of intervention for uncontrolled diabetes by a covering provider who does not know the patient well may be seen as appropriate . however , it results in additional delay in treatment ; in our study , the average interval between encounters was at least 7 weeks . a proactive approach where the pcp documents a specific plan of action could improve coordination of care and allow covering providers to take timely action , accelerating achievement of diabetes control . this study used natural language processing technology that permitted cost- and time - efficient computational analysis of thousands of patient encounters , including examination of hundreds of thousands of narrative provider notes in a matter of hours . in the future , similar technologies could also be used to monitor quality of patient care and/or supply feedback to providers . this feedback could help narrow the gap in care provided between pcps and covering providers if feedback is used consistently . the analysis focused on process - of - care measures that are tightly linked to better patient outcomes , allowing us to identify likely mechanisms for the beneficial effects of continuity of care . this was a large study , conducted in an ethnically and gender - diverse population , and thus is likely to be generalizable to other settings . this retrospective cohort study also has some limitations , beyond its inability to establish causality . instead , we focused on measures that have been shown to be tightly linked to patient outcomes . we used the cci as a measure of the patients ' overall disease burden in multivariable analyses . the cci was originally developed and validated for hospitalized patients and may therefore have skewed the results . however , the cci has also been shown to correlate with mortality in multiple outpatient populations ( 4547 ) , and the conditions it includes have face validity as predictors of mortality in both outpatients and inpatients . some of the data pertinent to the analysis might have been missing ; for example , physicians may not have recorded some of the bp measurements they made . if missing data were distributed unequally between different provider categories , it could have biased the study findings . to minimize this effect , we used bp information from structured emr records and also from narrative provider notes ( obtained using natural language processing ) where clinicians are more likely to document their own bp measurements . we have previously shown that this approach results in a more complete data collection ( 48 ) . physicians also might have been more likely to round the bp measurements down if they were individually judged according to bp - based quality indicators . however , no quality indicators were implemented at the individual provider level in the practices studied during the study period . the patients who seek care and the providers who work in such networks may be different from other populations . the practices we studied did not have a large number of midlevel providers , making it difficult to study the care they provide in more detail . furthermore , because no treatment algorithms were in place in any of the practices studied , midlevel providers who followed an algorithm could not be compared with those who did not . we did not have information on the patients ' health - related behaviors that could have accounted for some of the observed effects if they were distributed unequally between pcp versus non - pcp encounters . finally , we were unable to distinguish patients with type 1 diabetes from those with type 2 diabetes . because most of the patients studied likely had type 2 diabetes , our conclusions may not be applicable to patients with type 1 diabetes . in conclusion , this large , long - term retrospective study showed that pcps perform better on a number of critical process measures of diabetes care than covering physicians or midlevel providers . these findings suggest mechanisms for well - described improvements in quality of treatment seen with higher continuity of care . they should be taken into consideration in the design and evaluation of novel health care delivery models , such as patient - centered medical homes , and in quality improvement in traditional care settings .
objectivestudies have shown that patients without a consistent primary care provider have inferior outcomes . 
 however , little is known about the mechanisms for these effects . this study aims to determine whether primary care physicians ( pcps ) provide more frequent medication intensification , lifestyle counseling , and patient encounters than other providers in the primary care setting.research design and methodsthis retrospective cohort study included 584,587 encounters for 27,225 patients with diabetes and elevated a1c , blood pressure , and/or ldl cholesterol monitored for at least 2 years . 
 encounters occurred at primary care practices affiliated with two teaching hospitals in eastern massachusetts.resultsof the encounters documented , 83% were with pcps , 13% were with covering physicians , and 5% were with midlevel providers . in multivariable analysis , 
 the odds of medication intensification were 49% ( p < 0.0001 ) and 26% ( p < 0.0001 ) higher for pcps than for covering physicians and midlevel providers , respectively , whereas the odds of lifestyle counseling were 91% ( p 
 < 0.0001 ) and 21% ( p = 0.0015 ) higher . during visits with acute complaints , covering physicians were even less likely , by a further 52% ( p < 0.0001 ) , to intensify medications , and midlevel providers were even less likely , by a further 41% ( p < 0.0001 ) , to provide lifestyle counseling . compared with pcps , 
 the hazard ratios for time to the next encounter after a visit without acute complaints were 1.11 for covering physicians and 1.19 for midlevel providers ( p < 
 0.0001 for both).conclusionspcps provide better care through higher rates of medication intensification and lifestyle counseling . 
 covering physicians and midlevel providers may enable more frequent encounters when pcp resources are constrained .