The American Journal of Managed Care June 2011
Better Continuity of Care Reduces Costs for Diabetic Patients
Table 1 presents the characteristics of the study sample in 2001. The mean age of subjects was 60.65 years with the majority of patients being female, and 0.86% of them were of low-income status according to the government’s strict definition of the poverty line in Taiwan. With regard to the health status of patients, the average number of physician visits for any condition in the previous year was 28.42, which was higher than the national average of 15 visits, and the hospitalization rate in the previous year was 15.87%. Additionally, 47.23% of the study sample had a diabetes complication severity index score of 0, whereas 25.10% had a score of 2 or higher.
The study variables according to year are presented in Table 2. The COCI scores remained stable (0.64-0.66) from 2001 to 2006. In terms of healthcare utilization during this time period, the rate of diabetes-related hospitalizations increased from 13.59% to 20.64%, and the rate of ED visits increased from 6.67% to 11.95%. Additionally, diabetes-related pharmaceutical expenses increased from New Taiwan (NT) $16,428 to NT $23,728, and total diabetes-related healthcare expenses increased from NT $28,785 to NT $49,776 (NT $33 equaled $1 in 2001).
Table 3 presents results from the GEE models, which examined effects of COCI on the likelihood of diabetes-related hospitalization and ED visit. Patients with high or medium COCI scores were less likely to be hospitalized for diabetes-related conditions than were those with low COCI scores (odds ratio [OR] 0.26, 95% confidence interval [CI] 0.25, 0.27, and OR 0.58, 95% CI 0.56, 0.59, respectively). We also found that patients with high or medium COCI scores were less likely to have diabetes-related ED visits compared with patients with low COCI scores (OR 0.34, 95% CI 0.33, 0.36, and OR 0.64, 95% CI 0.62, 0.66, respectively).
Results from the GEE models concerning the effect of COCI on diabetes-related pharmaceutical and diabetes-related total healthcare expenses are listed in Table 4. Patients with high or medium COCI scores incurred lower pharmaceutical expenses than did patients with low COCI scores (ß –0.14, P <.001; ß –0.06, P <.001). Patients with high or medium COCI scores tended to incur lower diabetes-related total healthcare expenses than did patients with low COCI scores (ß –0.53, P <.001; ß –0.29, P <.001).
The Figure presents the mean predicted expenses, including diabetes-related pharmaceutical expenses and diabetesrelated total healthcare expenses, which were significantly different among the low, medium, and high COCI groups. With regard to pharmaceutical expenses, patients with low COCI scores spent NT $4155 more than did patients with high COCI scores. In terms of total healthcare expenses, we calculated a larger savings (NT $24,314) for patients with high COCI scores versus patients with low COCI scores.
We conducted 2 sensitivity analyses to improve the robustness of this study. First, we used the other 2 commonly used indicators of continuity of care to examine the association. The usual provider continuity index was defined as the number of outpatient visits to the most frequently seen physician divided by the total number of outpatient visits.28 The usual provider continuity index would therefore always be larger than zero, with a higher value corresponding to a higher continuity of care. In addition, the sequential continuity index was defined as the portion of consecutive visit pairs at which the same provider is seen.34 This score also ranges from 0 to 1, with a higher value representing a better continuity-of-care status. We found that the results were similar to those obtained using COCI (eAppendix A and eAppendix B, available at www.ajmc.com). Second, we also examined whether the effect of the COCI on healthcare utilization and healthcare expense was independent of the number of physician visits. We stratified the number of physician visits into 3 tertiles (low-visit, medium-visit, and high-visit groups) and found almost similar results within each group (eAppendix C and eAppendix D, available at www.ajmc.com).
We examined the effects of continuity of care on healthcare utilization and healthcare expenses for patients with DM by calculating COCI scores for diabetes-related visits. The COCI scores ranged from 0.64 to 0.66, which were higher than the COCI scores for all physician visits among the general public reported in a previous study.6 Findings from our analysis showed that better continuity of care was significantly associated with a lower likelihood of diabetes-related hospitalizations and ED visits. This study also found that better continuity of care for DM was significantly associated with lower diabetes-related pharmaceutical expenses and diabetesrelated total healthcare expenses.
The COCI scores using only diabetes-related visits in these years (0.64-0.66) are higher than the scores calculated using all visits (0.35-0.36). Under Taiwan’s NHI, patients can visit a specialist without referral; a high COCI score implies that many diabetic patients tend to see the same doctors for diabetes care. The COCI scores tend to be much lower for visits for all conditions, indicating poorer continuity of care in general. However, COCI scores are difficult to interpret in absolute numbers and should not be compared with other findings from different healthcare systems.
In terms of the effects of continuity of care on healthcare utilization, our findings were similar to those of previous studies focusing on patients with diabetes. Knight et al found that better continuity of care by family physicians was associated with decreased hospitalization among the elderly with diabetes in Canada.13 A study by Lin et al found that a higher level of continuity of care was associated with a lower risk of hospitalization for diabetic complications among patients with diabetes in Taiwan.14 By using a longitudinal study analysis to account for repeated measures from the same patients, this study enhanced the robustness of previous findings. Furthermore, we also found that better continuity of care may lead to a lower likelihood of diabetes-related ED visits. The findings imply that increased continuity of care for DM may result in better healthcare outcomes.
Previous studies have shown that better continuity of care is associated with lower healthcare expenses in general. Weiss et al found that longer relationships between physicians and patients were associated with a lower cost of inpatient and outpatient care for the elderly in the United States.35 Raddish et al reported a negative relationship between continuity of care and prescription costs for 5 target diseases in the United States.36 Similarly, De Maeseneer et al reported significant effects of continuity of care on total healthcare costs in family practices in Belgium.37 Our study contributes to this current literature by focusing on expenses related to diabetes care.
We found that diabetic patients with a high level of continuity of care incurred lower annual expenses for medications and healthcare overall, spending NT $4155 less (approximately $126) for medications and NT $24,314 less (approximately $737) for healthcare overall than did those patients with a low level of continuity of care in Taiwan. The reduced pharmaceutical and healthcare expenses could be explained by the ongoing relationship between the healthcare provider and the patient, which may improve guideline adherence,9 reduce unnecessary laboratory testing and test repetition,38,39 and avoid polypharmacy.40 Additionally, reduced healthcare expenses may be associated with fewer hospital admissions or ED visits that result from poor control of diabetes. However, determining the mechanism of this effect is beyond the scope of this study and is worthy of further exploration.
Limitations to this study need to be addressed. First, we did not include certain patient characteristics that may simultaneously affect both the continuity of care and healthcare outcomes; these include socioeconomic variables and healthseeking behaviors. However, we used a longitudinal analysis technique that was able to account for the time-invariant, unobserved patient characteristics, thus increasing the robustness of the findings. Second, this study utilized NHI claims data, which do not contain information about self-paid physician visits. We assumed that the proportion of such visits would be minimal with respect to total healthcare visits in Taiwan. Finally, there are some unique aspects of Taiwan’s healthcare system and thus the results may not be generalizable to other populations.
In conclusion, in a healthcare system with universal coverage and a high level of access to care, this study indicates that better continuity of care is associated with less healthcare utilization and lower healthcare expenses for diabetic patients. Improving the continuity of care might be beneficial for patients with DM.
The authors would like to thank National Health Research Institutes for providing the data sets for our study.
Author Affiliations: From Institute of Health Policy & Management (CCC, SHC), College of Public Health, National Taiwan University, Taiwan.
Funding Source: The study was supported by a grant from the National Science Council (NSC98-2410-H-002-054) in Taiwan.
Author Disclosures: The authors (CCC, SHC) report no relationship or financial interest with any entity that would pose a conflict of interest with the subject matter of this article.
Authorship Information: Concept and design (CCC, SHC); acquisition of data (SHC); analysis and interpretation of data (CCC, SHC); drafting of the manuscript (CCC, SHC); critical revision of the manuscript for important intellectual content (CCC, SHC); statistical analysis (CCC, SHC); provision of study materials or patients (CCC, SHC); obtaining funding (SHC); administrative, technical, or logistic support (CCC); and supervision (SHC).
Address correspondence to: Shou-Hsia Cheng, PhD, Institute of Health Policy & Management, National Taiwan University, 17 Xu-Zhou Road, Taipei, Taiwan 100. E-mail: firstname.lastname@example.org.
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