The objective of this study was to describe the burden of multiple chronic diseases on the patient and the ambulatory health care system. Our results demonstrate three key trends. First, while the burden of disease on the patient, as measured by mean number of ambulatory health care visits per year, was higher for those with multiple chronic diseases, the overall impact on the primary health care system was relatively small. Second, across all disease counts and ages there were many more visits to primary health care physicians compared to specialist physicians. This trend was evident even among the most elderly patients who, with age, had ever-increasing visits to primary health care physicians, while the number of visits to specialist physicians declined. Third, we found that, while the number of primary health care visits increased with age, the elderly with no diseases had many fewer visits per year, compared to younger adults with multiple chronic diseases.
Our findings confirm what other research has suggested about the high burden of chronic disease on the individual patient [3, 4, 11]. Recently, the Canadian Institute for Health Information reported results of a national survey that found more than twice the rate of reported visits to a family doctor among seniors with three or more diseases, compared to seniors with only one chronic disease . Using data from the 2005 Canadian Community Health Survey, those with multiple chronic diseases represented 12% of the population but they accounted for 24% of all primary health care visits and 25% of all specialist consultations . In that study the mean annual number of consultations with a family doctor was 4.0 in general population, 3.1 for those with no diseases, 4.7 with 1 disease and 7.4 for those with three or more diseases; estimates that are very close to our results.
Importantly, our study demonstrates that patients with multiple chronic diseases do not drive overall primary health care use in Ontario because prevalence of multiple chronic diseases in the population remains low. The majority of primary health care visits continue to be made by adults who have no or one disease. Future research could assess time trends to see if this pattern is changing, given the predicted rise in the prevalence of multiple chronic diseases with the aging population.
We acknowledge that a number of important chronic diseases were excluded from this study, such as depression and joint disease. This may have resulted in an overestimation of the number of persons with no or one disease. Although the exclusion of these diseases may change prevalence estimates and the associated number of visits, we do not believe this has an impact on the patterns of health care utilization we found. If anything, our results are an underestimation of the overall burden of multiple chronic diseases on the primary health care system. Validation studies for the ascertainment methods for additional chronic diseases in the Ontario databases are an ongoing effort at ICES.
Canada has a strong primary health care system and primary health care providers act as gatekeepers to specialist services. Thus, it was not surprising to see that there were more primary health care visits in our study, particularly among the very elderly. The lower rate of specialist visits in the very elderly can be explained by factors such as fewer new disease diagnoses that require specialist consultation and primary care provider or patient preference for less intervention and testing. Our results are different from a U.S. study of Medicare beneficiaries where the burden of care for non-elderly patients (<65 years) with high levels of morbidity fell disproportionately on primary health care but this pattern did not hold for the elderly who had more specialist compared to primary health care visits . This may, in part, be due to the broader age categories used in the American study but could also reflect a real difference in the use of specialist and primary health care services in these two countries. The appropriate number of visits to primary health care and specialist services is difficult to establish but this research points to the continued need for a robust primary health care workforce.
Recent attention has focused on determining the relative impact of age and chronic disease burden on health system utilization . In their 2011 report, the Canadian Institute for Health Information used data from the Canadian Survey of Experiences With Primary Health Care to report on the impact of chronic diseases . In that study, the total number of chronic diseases was more important than age in predicting the annual number of health care visits made by seniors. In each of the age groups (65 to 74 years, 75 to 84 years, and 85 years and older), those with three or more reported chronic diseases had nearly three times the total number of primary health care visits compared to seniors with no reported chronic diseases. We report on the impact of age and disease count by looking at annual mean number of primary health care visits and find that, at a patient level, primary health care visits increased with both the number of diseases and also with age. The relative importance of these two factors (age and number of diseases) should be explored in future studies using statistical modeling.
This study has limitations common to all research using administrative data. These databases were constructed to serve a billing role and, thus, while they are rich in information, they were not created for research or disease ascertainment. To limit errors in our disease estimates we have used highly validated definitions of chronic diseases, but we acknowledge the possibility of over and under-ascertainment of disease. Furthermore, we estimated primary health care service use exclusively by looking at the number of visits and did not look at other health care services controlled by primary care, such as outpatient laboratory and diagnostic testing or number of prescriptions. Future research could explore these services to see if the patterns we identified hold.