we conducted a cross - sectional analysis of electronic messaging activity at group health cooperative between 1 january 2004 and 31 march 2005 . all study variables were abstracted from clinical and administrative data repositories using sas , version 8 . the study was conducted at group health cooperative  a mixed - model health care financing and delivery organization in washington and north idaho . over 300,000 members receive care through group health cooperative integrated delivery system , which includes 20 group health cooperative  owned facilities and over 500 group health cooperative physicians . beginning in august 2003 , all patients in the integrated delivery system were able to access patient web services through the mygrouphealth web site . these services include prescription refills , appointment scheduling , medical record access , and secure messaging to contact health care team members as previously described ( 6 ) . at the initial level ( registration only ) , a patient created a password - protected account on the web site . at this level , the user could not exchange personally identifiable health information with group health cooperative providers but could access discussion groups on several topics . a facilitator was employed to review all content and remove any personally identifiable content . a second , higher level of security provides access to the medical record , secure messaging , and other advanced web services . access to this security level required each patient to complete an additional step verifying the patient 's identity . at this level of security patients could obtain identity verification through an online request or in person at a group health cooperative clinic with a driver 's license or a passport . patient services on the mygrouphealth web site the study was restricted to diabetic patients aged > 18 years who were continuously enrolled in group health cooperative 's integrated group practice during the study period . patients were identified as having diabetes by three or more outpatient icd-9 diagnoses for diabetes during 2 years before the study period . we divided the study population into several groups , depending on their level of web service use ( fig . , 34% completed the process of identity verification to gain access to secure messaging and other advanced services . this group was further divided into two subgroups : members who used secure messaging at least once during the study period ( secure messaging users ) and members who had obtained identity verification but did not use secure messaging during the study period ( identity verified ) . the identity - verified group subjects were selected as the primary comparison cohort because they were expected to be most similar to the secure messaging users in terms of unmeasured characteristics ( fig . the group of patients who had no prior mygrouphealth registration or who elected to obtain only basic username and password access was designated as a secondary comparison cohort ( nonverified ) . overview of study cohorts .. three diabetes - related quality - of - care indicators were selected to assess care quality : a1c < 7% , blood pressure 130/80 mmhg , and ldl cholesterol < 100 mg / dl ( 7 ) . message threads , rather than individual messages , were used to quantify secure messaging activity . a thread was defined as the set of messages related to an original message by successive replies . a prior analysis of patient - provider messaging patterns at group health cooperative has suggested that a message thread is most conceptually similar to a single episode of clinical care . for example , during 2004 , 96% of all threads contained 5 or fewer messages , 86% spanned 3 calendar days , and 99.7% contained fewer than 10 messages ( 8) . patient age and sex were abstracted from administrative databases . twelve adjusted diagnostic groups were selected a priori to control for medical comorbidity ( 9 ) . icd-9 data were used to generate a count of complications to control for diabetes severity ( 10 ) . depression severity was modeled as an ordinal variable with four levels ( g. simon , personal communication ) . a history of depression was defined by three or more outpatient visits with an icd-9 diagnosis of depression in the year before the study . moderate depression was defined by any diagnosis of depression by a psychiatrist or other mental health specialist , and severe depression was defined by any inpatient mental health admission . insurance was grouped into the following three categories : commercial , medicare , or medicaid . members with medicaid insurance were grouped with members in washington state 's basic health plan  an insurance program for low - income individuals not qualifying for medicaid . primary care provider ( pcp ) participation in secure messaging was measured as a percent of total outpatient encounters . low neighborhood socioeconomic status was defined as a neighborhood where at least 20% of the population earned < 20,000 usd per year or at least 25% of adults aged > 25 years had less than a high - school education ( 11 ) . census data were further used to determine rural or urban residence , and home address records were used to calculate the distance from home to clinic . provider 's sex and specialty , quintile rank of age , the proportion of secure messaging threads that were provider initiated , and the average provider response time were abstracted from administrative databases . multivariable regression models were used to examine the association between secure messaging use and care quality . a second set of models was generated to examine the association between secure messaging use and the number of outpatient visits . the patient was the unit of analysis for all regression models , with clustering by pcp . log - linear models were used to estimate relative risks ( rrs ) or rate ratios . models were adjusted for age , sex , overall medical comorbidity , diabetes severity , depression severity , insurance , and pcp 's age , sex , and participation in secure messaging . to ensure a flexible specification and minimize residual confounding , age neighborhood - level racial / ethnic and socioeconomic status measures were not significant in preliminary models and were dropped from the final models . generalized estimating equations were used to estimate regression coefficients ( 12 ) , and the huber - white robust sandwich estimator was used for variance estimates ( 13 ) . the wald tests were used to assess the significance of explanatory variables , using two - sided p values evaluated at the 0.05 significance level . the study was restricted to diabetic patients aged > 18 years who were continuously enrolled in group health cooperative 's integrated group practice during the study period . patients were identified as having diabetes by three or more outpatient icd-9 diagnoses for diabetes during 2 years before the study period . we divided the study population into several groups , depending on their level of web service use ( fig . , 34% completed the process of identity verification to gain access to secure messaging and other advanced services . this group was further divided into two subgroups : members who used secure messaging at least once during the study period ( secure messaging users ) and members who had obtained identity verification but did not use secure messaging during the study period ( identity verified ) . the identity - verified group subjects were selected as the primary comparison cohort because they were expected to be most similar to the secure messaging users in terms of unmeasured characteristics ( fig . the group of patients who had no prior mygrouphealth registration or who elected to obtain only basic username and password access was designated as a secondary comparison cohort ( nonverified ) . three diabetes - related quality - of - care indicators were selected to assess care quality : a1c < 7% , blood pressure 130/80 mmhg , and ldl cholesterol < 100 mg / dl ( 7 ) . message threads , rather than individual messages , were used to quantify secure messaging activity . a thread was defined as the set of messages related to an original message by successive replies . a prior analysis of patient - provider messaging patterns at group health cooperative has suggested that a message thread is most conceptually similar to a single episode of clinical care . for example , during 2004 , 96% of all threads contained 5 or fewer messages , 86% spanned 3 calendar days , and 99.7% contained fewer than 10 messages ( 8) . twelve adjusted diagnostic groups were selected a priori to control for medical comorbidity ( 9 ) . icd-9 data were used to generate a count of complications to control for diabetes severity ( 10 ) . depression severity was modeled as an ordinal variable with four levels ( g. simon , personal communication ) . a history of depression was defined by three or more outpatient visits with an icd-9 diagnosis of depression in the year before the study . moderate depression was defined by any diagnosis of depression by a psychiatrist or other mental health specialist , and severe depression was defined by any inpatient mental health admission . insurance was grouped into the following three categories : commercial , medicare , or medicaid . members with medicaid insurance were grouped with members in washington state 's basic health plan  an insurance program for low - income individuals not qualifying for medicaid . primary care provider ( pcp ) participation in secure messaging was measured as a percent of total outpatient encounters . low neighborhood socioeconomic status was defined as a neighborhood where at least 20% of the population earned < 20,000 usd per year or at least 25% of adults aged > 25 years had less than a high - school education ( 11 ) . census data were further used to determine rural or urban residence , and home address records were used to calculate the distance from home to clinic . provider 's sex and specialty , quintile rank of age , the proportion of secure messaging threads that were provider initiated , and the average provider response time were abstracted from administrative databases . multivariable regression models were used to examine the association between secure messaging use and care quality . a second set of models was generated to examine the association between secure messaging use and the number of outpatient visits . the patient was the unit of analysis for all regression models , with clustering by pcp . log - linear models were used to estimate relative risks ( rrs ) or rate ratios . models were adjusted for age , sex , overall medical comorbidity , diabetes severity , depression severity , insurance , and pcp 's age , sex , and participation in secure messaging . to ensure a flexible specification and minimize residual confounding , age was modeled using linear splines . neighborhood - level racial / ethnic and socioeconomic status measures were not significant in preliminary models and were dropped from the final models . generalized estimating equations were used to estimate regression coefficients ( 12 ) , and the huber - white robust sandwich estimator was used for variance estimates ( 13 ) . the wald tests were used to assess the significance of explanatory variables , using two - sided p values evaluated at the 0.05 significance level . thirty - four percent of the study cohort completed the process of identity verification for use of advanced web services including secure messaging ( n = 5,274 ) ( overall study cohort included 15,427 subjects ) . of the patients who obtained identity verification , 55% went on to use secure messaging ( n = 2,924 ) . secure messaging users participated in an average of 5.3 threads , consisting of 11.8 individual messages . altogether the mean age of the secure messaging cohort was 58 years , whereas the mean age of the nonmessaging subgroups was 63 years ( table 2 ) . among the subgroup with at least 12 secure messaging threads per year , 77% had high or very high expected resource use compared with 44% of the identity - verified cohort . population characteristics data are % or means  sd . * patients with no mygrouphealth web site registration or only basic username / password registration . patients who registered to use the mygrouphealth web site and completed secondary identity verification but never used secure messaging . sixty - four percent of pcps with high secure messaging use were female compared with 37% of pcps with low secure messaging use ( table 3 ) . ten percent of pcps with high secure messaging use and 32% of pcps with low secure messaging use had panels of over 2,000 patients . unadjusted rrs are presented in table 4 ( model a ) . in multivariable models , the rate of a1c < 7% was 36% higher in patients with the highest rate of secure messaging use ( 12 threads per year ) compared with that in the nonmessaging identity - verified comparison cohort ( rr 1.36 [ 95% ci 1.161.58 ] ) ( table 4 ) . in contrast , secure messaging use was not associated with control of blood pressure < 130/80 mmhg . there was a small but statistically significant association between secure messaging and ldl cholesterol < 100 mg / dl . for all three quality measures , the nonmessaging identity - verified cohort had slightly better outcomes than the nonmessaging non - verified cohort . model b is adjusted for age , sex , overall medical comorbidity , diabetes severity , depression severity , insurance type , pcp 's participation in secure messaging , pcp 's age , pcp 's sex , and pcp panel size . * the primary care visit rate was 32% higher among patients with high use of secure messaging compared with that in the nonmessaging comparison cohort ( rr 1.32 [ 95% ci 1.191.45 ] ) ( table 4 ) . this translates to approximately three to four additional outpatient office visits , given a baseline visit rate of nine visits per year . high secure messaging users also had more outpatient specialty visits ( 1.43 [ 1.251.64 ] ) ( table 4 ) and emergency care visits ( 1.66 [ 1.232.26 ] ) ( table 4 ) than the nonmessaging comparison cohort . in this cross - sectional study , patients who used more secure messaging had better glycemic control . care providers may have used secure messaging to recommend medication changes between in - person visits , thereby optimizing treatment regimens more quickly . medication intensification has previously been found to be the most significant predictor of variation in a1c ( 14 ) . by increasing the frequency of contact , secure messaging might also strengthen continuity of care , which has also been associated with improved glycemic control ( 15 ) . as with all observational studies , unmeasured differences between users and nonusers of secure messaging may also explain our results . users of secure messaging may have had higher health literacy , education , or other characteristics that are also found among individuals with better glycemic control . patients who engage in secure messaging may also be more engaged in self - care behaviors that promote better glycemic control . finally , it is possible that use of advanced web services other than secure messaging , which included prescription refills , appointment scheduling , and medical record access , may explain some of these results . among patients who did not use secure messaging , the cohort who had access to advanced web services exhibited slightly better control of a1c , blood pressure , and ldl cholesterol than the cohort without access . contrary to our hypothesis , we found a positive association between secure messaging use and the number of outpatient visits . two prior longitudinal studies of physicians have found electronic messaging systems to be associated with a reduction in outpatient visit rates ( 4,5 ) . these studies suggest that electronic consultations may substitute for traditional in - person office visits . patients with diabetes who use secure messaging may be more proactive with care providers both online and in person and may use secure messaging as a complement to care rather than as a substitute . secure messaging use may also raise unmet needs in this population that require further engagement either in person or through secure messaging . this is the one of the first studies to examine the association among electronic patient - provider messaging , diabetes - related health outcomes , and outpatient utilization in a large health care delivery system . although several important studies have been published in this area over the past 5 years , most are limited by small sample sizes . in contrast , a key strength of our study is its setting : a large nonprofit health care system that serves 300,000 members . limitations include the cross - sectional design of the study , the short duration of exposure to secure messaging , and potential self - selection bias . secure messaging users may have differed from nonusers by unmeasured factors such as self - efficacy , attitudes toward medical care , race , socioeconomic status , and health literacy . given the cross - sectional design of this study , it is impossible to conclude that electronic messaging caused the outcomes that we observed . randomized controlled trials or longitudinal analyses will be required to assess the causal relationship among secure messaging and utilization , care quality , and health outcomes . as physicians and health care organizations consider how and when to support electronic communication with patients , we must understand how this new care environment differs from traditional in - person care . secure messaging may serve as an important part of care for patients with diabetes and an opportunity to support them in self - management outside of routine visits . our findings suggest that patients with diabetes who are frequent users of electronic patient - provider messaging systems may represent a unique patient population , characterized by better glycemic control and a greater use of outpatient visits . in this cross - sectional study , patients who used more secure messaging had better glycemic control . care providers may have used secure messaging to recommend medication changes between in - person visits , thereby optimizing treatment regimens more quickly . medication intensification has previously been found to be the most significant predictor of variation in a1c ( 14 ) . by increasing the frequency of contact , secure messaging might also strengthen continuity of care , which has also been associated with improved glycemic control ( 15 ) . as with all observational studies , unmeasured differences between users and nonusers of secure messaging may also explain our results . users of secure messaging may have had higher health literacy , education , or other characteristics that are also found among individuals with better glycemic control . patients who engage in secure messaging may also be more engaged in self - care behaviors that promote better glycemic control . finally , it is possible that use of advanced web services other than secure messaging , which included prescription refills , appointment scheduling , and medical record access , may explain some of these results . among patients who did not use secure messaging , the cohort who had access to advanced web services exhibited slightly better control of a1c , blood pressure , and ldl cholesterol than the cohort without access . contrary to our hypothesis , we found a positive association between secure messaging use and the number of outpatient visits . two prior longitudinal studies of physicians have found electronic messaging systems to be associated with a reduction in outpatient visit rates ( 4,5 ) . these studies suggest that electronic consultations may substitute for traditional in - person office visits . patients with diabetes who use secure messaging may be more proactive with care providers both online and in person and may use secure messaging as a complement to care rather than as a substitute . secure messaging use may also raise unmet needs in this population that require further engagement either in person or through secure messaging . this is the one of the first studies to examine the association among electronic patient - provider messaging , diabetes - related health outcomes , and outpatient utilization in a large health care delivery system . although several important studies have been published in this area over the past 5 years , most are limited by small sample sizes . in contrast , a key strength of our study is its setting : a large nonprofit health care system that serves 300,000 members . limitations include the cross - sectional design of the study , the short duration of exposure to secure messaging , and potential self - selection bias . secure messaging users may have differed from nonusers by unmeasured factors such as self - efficacy , attitudes toward medical care , race , socioeconomic status , and health literacy . given the cross - sectional design of this study , it is impossible to conclude that electronic messaging caused the outcomes that we observed . randomized controlled trials or longitudinal analyses will be required to assess the causal relationship among secure messaging and utilization , care quality , and health outcomes . as physicians and health care organizations consider how and when to support electronic communication with patients , we must understand how this new care environment differs from traditional in - person care . secure messaging may serve as an important part of care for patients with diabetes and an opportunity to support them in self - management outside of routine visits . our findings suggest that patients with diabetes who are frequent users of electronic patient - provider messaging systems may represent a unique patient population , characterized by better glycemic control and a greater use of outpatient visits .
objectiveto test the hypothesis that electronic patient - provider messaging is associated with high care quality for diabetes and lower outpatient utilization.research design and methodswe conducted a cross - sectional analysis of electronic patient - provider messaging over a 15-month period between 1 january 2004 and 31 march 2005 . 
 the study was set at group health cooperative  a consumer - governed , nonprofit health care system that operates in washington and idaho . 
 participants included all patients aged 18 years with a diagnosis of diabetes . 
 in addition to usual care , all patients had the option to use electronic messaging to communicate with their care providers . 
 the primary outcome measures were diabetes - related quality - of - care indicators ( a1c , blood pressure , and ldl cholesterol ) and outpatient visits ( primary care , specialty care , and emergency).resultsnineteen percent of patients with diabetes used electronic messaging to communicate with their care providers during the study period ( n = 2,924 ) ( overall study cohort : 15,427 subjects ) . in multivariate models , frequent use of electronic messaging was associated with a1c 
 < 7% ( relative risk [ rr ] 1.36 [ 95% ci 1.161.58 ] ) . 
 contrary to our hypothesis , frequent use of electronic messaging was also associated with a higher rate of outpatient visits ( 1.39 [ 1.261.53]).conclusionsfrequent use of electronic secure messaging is associated with better glycemic control and increased outpatient utilization . 
 electronic patient - provider communication may represent one strategy to meet the health care needs of this unique population . 
 more research is necessary to assess the effect of electronic messaging on care quality and utilization .