Effect of number and type of antidiabetes medications on adherence and glycemia of ambulatory type 2 diabetes patients in southwestern Nigeria
Main Article Content
Keywords
Medication Adherence, Blood Glucose, Polypharmacy, Health Knowledge, Attitudes, Practice, Nigeria, Diabetes Mellitus Type 2,
Abstract
Objective: To determine the influence of number and type of antidiabetes medications on adherence and glycemia of ambulatory type 2 diabetes patients in southwestern Nigeria.
Methods: A cross-sectional study using pre-tested structured questionnaire among 176 consented patients recruited from the endocrinology clinics of two teaching hospitals between November, 2010 and January, 2011; and a retrospective review of case notes of the cohort for details of prescribed medications and blood glucose values. Descriptive statistics were used to summarize the data. Tests of proportions were evaluated using Chi-square or Fisher’s exact test as appropriate. The differences in mean fasting blood glucose (FBG) between and among categorical variables were compared using student t-test and ANOVA respectively, with p<0.05 considered significant.
Results: Mean number of prescribed medications was 4.6±1.4. Almost two thirds 103 (60.6%) were placed on >4 medications. Adherence was better among patients on >4 medications compared to those on ≤4 medications (p=0.05). However, patients on >4 medications were mostly older adults (>60 years of age), and they were in the majority (66.7%) who had tertiary education compared to 33.3% of those on ≤4 medications who had tertiary education (p=0.02). Adherence rates to antidiabetes medications were in the ranking of oral antidiabetes medications (OAM) alone (50.0%) > insulin plus OAM (44.0%) > insulin alone (41.7%) with no significant difference (p=0.77). There was a significant difference in mean FBG among patients on >4 medications (172.1 ±61.1mg/dL) versus (198.8 ±83.8mg/dL) among those on ≤4 medications (p=0.02).
Conclusion: Prescribing more than four medications is linked to improved adherence and glycemic outcome. However, age and educational background of patients are important factors that need to be considered when prescribing multiple medications for type 2 diabetes.
References
1. Drass J, Kell S, Osborn M, Bausell B, Corcoran J Jr, Moskowitz A, Fleming B. Diabetes care for Medicare beneficiaries. Attitudes and behaviors of primary care physicians. Diabetes Care. 1998;21(8):1282-1287.
2. Fincham JE, Wertheimer AI. Using the health belief model to predict initial drug therapy defaulting. Soc Sci Med. 1985;20(1):101-105.
3. Smith MC. Predicting and detecting noncompliance. In: Social and Behavioural Aspect of Pharmaceutical Care. Smith MC, Wertheimer AI eds. New York, NY: Pharmaceutical Products Press. 1996.
4. World Health Organization. Adherence to long-term therapies: Evidence for action. WHO 2003. Geneva. Switzerland. Available at http://www.who.int/chp/knowledge/publications/adherence_report/en/index.html (Accessed 2012, March 20).
5. Osterberg L, Blaschke T. Adherence to medication. N Engl J Med. 2005;353(5):487-497.
6. Wild S, Roglic G, Green A, Sicree R, King H. Global prevalence of diabetes: estimates for the year 2000 and projections for 2030. Diabetes Care. 2004;27(5):1047-1053.
7. World Health Organization. Prevention of diabetes mellitus. Report of a WHO Study Group. WHO Technical Report series 844, Geneva;WHO:1994.
8. Amos AF, McCarty DJ, Zimmet P. The rising global burden of diabetes and its complication, estimates and projection to the year 2010. Diabet Med. 1997;14(Suppl 5):S1-S85.
9. Unwin N, Sobugivi E, Alberto KGMM. Type 2 diabetes: the challenge of preventing a global epidemic. Diabetes International. 2001;11:4-8.
10. Shams ME, Barakat EA. Measuring the rate of therapeutic adherence among outpatients with type 2 diabetes mellitus in Egypt. Saudi Pharm J. 2010;18(4):225-232. doi: 10.1016/j.jsps.2010.07.004
11. Schechter CB, Walker EA. Improving Adherence to Diabetes Self-management Recommendations. Diabet Spectr. 2002;15(3):170-175. doi: 10.2337/diaspect.15.3.170
12. Vermeire E, Royen PV, Coenen S, Wens J, Denekans J. The adherence of type 2 diabetes patients to their therapeutic regimens: a qualitative study from the patients’ perspective. Pract Diabet Int. 2003;20(6):209-214.
13. Haynes RB, Yao X, Degani A, Kripalani S, Garg A, McDonald HP. Interventions for enhancing medication adherence. Cochrane Database Syst Rev. 2005;(4):CD000011. doi:10.1002/14651858
14. Cramer JA. Relationship between medication compliance and medical outcomes. Am J Health Syst Pharm. 1995;52(14 Suppl 3):S27-S29.
15. Dunbar-Jacob J, Erlen JA, Schlenk EA, Ryan CM, Sereika SM, Doswell WM. Adherence in chronic disease. Annu Rev Nurs Res. 2000;18:48-90.
16. National Pharmaceutical Council. Noncompliance with medical regimens: detection and intervention. Qual Thr Res. 1992;2(3):1-20.
17. Maddigan SL, Feeny DH, Johnson JA. Health related quality of life deficits associated with diabetes and comorbities in a Canadian national population health survey. Qual Life Res. 2005;14(5):1311-1320.
18. Vermeire E, Wens J, Van Royen P, Biot Y, Hearnshaw H, Lindenmeyer A. Interventions for improving adherence to treatment recommendations in people with type 2 diabetes mellitus Cochrane Database Syst Rev. 2005;(2):CD003638.
19. Morgan CL, Currie CJ, Peters JR. Relationship between diabetes and mortality: a population study using record linkage. Diabetes Care. 2000;23(8):1103-1107.
20. Andersson DK, Svärdsudd K. Long-term glycemic control relates to mortality in type 2 diabetes. Diabetes Care. 1995;18(12):1534-43.
21. The Diabetes Control and Complications Trial Research Group. The effect of intensive treatment of diabetes on the development and progression of long-term complications in insulin-dependent diabetes mellitus. N Engl J Med. 1993;329(14):977-986.
22. Lim PC, Lim K. Evaluation of a pharmacist-managed diabetes medication therapy adherence clinic. Pharm Pract. 2010;8(4):250-254.
23. United Kingdom prospective Diabetes Study Group. Intensive blood glucose control with sulfonylurea or insulin compared with conventional treatment and risk of complication in patients with type 2 diabetes (UKPDS 33). Lancet. 1998;352(9131):837-853.
24. Stratton IM, Adler AI, Neil HA, Matthews DR, Manley SE, Cull CA, Hadden D, Turner RC, Holman RR. Association of glycaemia with macrovascular and microvascular complications of type 2 diabetes (UKPDS 35): prospective observational study. BMJ. 2000;321(7258):405-412.
25. Glasgow RE. Compliance to diabetes regimens. Conceptualization, complexity, and determinants. In: Patient Compliance in Medical Practice and Clinical Trials. Cramer JA, Spiker B (eds). Raven Press: New York, NY;1994.
26. Horne R. Adherence to medication: a review of the existing literature. In: Adherence to treatment in medical conditions. Myers LB, Midence K (eds). Harwood Academic Press: Amsterdam; 1998.
27. Blackwell B. Drug therapy. Patient compliance. N Engl J Med. 1973;289(5):249-252.
28. American Diabetes Association. Standards of medical care in diabetes 2006. Diabet Care 2006;29 (Suppl 1):S4-S42.
29. Kroenke K, Pinholt EM. Reducing polypharmacy in the elderly: a controlled trial of physician feedback. J Am Geriatr Soc. 1990;38(1):31-36.
30. Sica DA. Rationale for fixed-dose combinations in the treatment of hypertension: the cycle repeats. Drugs. 2002;62(3):443-462.
31. Bakris GL. The role of combination anti-hypertensive therapy and the progression of renal disease hypertension: looking toward the next millennium. Am J Hypertens. 1998;11(10):158S-162S.
32. Grant RW, Cagliero E, Murphy-Sheehy P, Singer DE, Nathan DM, Meigs JB. Comparison of hyperglycemia, hypertension, and hypercholesterolemia management in patients with type 2 diabetes. Am J Med. 2002;112(8):603-609.
33. Adisa R, Alutundu MB, Fakeye TO. Factors contributing to nonadherence to oral hypoglycemic medication among ambulatory type 2 diabetes patients in southwestern Nigeria. Pharm Pract. 2009;7(3):163-169.
34. Cramer JA. A systematic review of adherence with medications for diabetes. Diabetes Care. 2004;27(5):1218-1224.
35. United Kingdom Prospective Diabetes Study Group. Effect of intensive blood-glucose control with metformin on complications in overweight patients with type 2 diabetes (UKPDS 34). Lancet. 1998;352(9131):854-865.
36. The Creative Research Systems. The complete survey software solution since 1982. Research Aids. Available at http://www.surveysystem.com/sscal.html (Accessed 2011, December 26).
37. Morisky DE, Green LW, Levine DM. Concurrent and predictive validity of a self-reported measure of medication adherence. Med Care. 1986;24(1):67-74.
38. Shalansky SJ, Levy AR, Ignaszewski AP. Self-reported Morisky Score for identifying nonadherence with cardiovascular medications. Ann Pharmacother. 2004;38(9):1363-1368.
39. Vik SA, Maxwell CJ, Hogan DB, Patten SB, Johnson JA, Romonko-Slack L. Assessing medication adherence among older persons in community settings. Can J Clin Pharmacol. 2005;12(1):e152-e164.
40. Fulton MM, Allen ER. Polypharmacy in the elderly: a literature review. J Am Acad Nurse Pract. 2005;17(4):123-132.
41. Fraizer SC. Health outcomes and polypharmacy in elderly individuals: an integrated literature review. J Gerontol Nurs. 2005;31(9):4-11.
42. Bjerrum L, Rosholm JU, Hallas J, Kragstrup J. Methods for estimating the occurrence of polypharmacy by means of a prescription database. Eur J Clin Pharmacol. 1997;53(1):7-11.
43. Grant RW, Devita NG, Singer DE, Meigs JB. Polypharmacy and medication adherence in patients with type 2 diabetes. Diabetes Care. 2003;26(5):1408-1412.
44. Blonde L. Management of type 2 diabetes: update on new pharmacological options. Manag Care. 2000;9(8 Suppl):11-17.
45. Brown AF, Mangione CM, Saliba D, Sarkisian CA; California Healthcare Foundation/American Geriatrics Society Panel on Improving Care for Elders with Diabetes. Guidelines for improving the care of the older person with diabetes mellitus. J Am Geriatr Soc. 2003;51(5 Suppl Guidelines):S265-S280.
46. Bethel MA, Sloan FA, Belsky D, Feinglos MN. Longitudinal incidence and prevalence of adverse outcomes of diabetes mellitus in elderly patients. Arch Intern Med. 2007;167(9):921-927.
47. Patel I, Chang J, Shenolikar RA, Balkrishman R. Medication adherence in low income elderly type 2 diabetes patients: a retrospective cohort study. Int J Diabet Mellit. 2010;2(2):122-124.
48. Knowler WC, Barrett-Connor E, Fowler SE, Hamman RF, Lachin JM, Walker EA, Nathan DM; Diabetes Prevention Program Research Group. Reduction in the incidence of type 2 diabetes with lifestyle intervention or metformin. N Engl J Med. 2002;346(6):393-403.
49. Wing RR, Hamman RF, Bray GA, Delahanty L, Edelstein SL, Hill JO, Horton ES, Hoskin MA, Kriska A, Lachin J, Mayer-Davis EJ, Pi-Sunyer X, Regensteiner JG, Venditti B, Wylie-Rosett J; Diabetes Prevention Program Research Group. Achieving weight and activity goals among diabetes prevention program lifestyle participants. Obes Res. 2004;12(9):1426-1434.
50. McCulloch DK, Munshi M. Treatment of type 2 diabetes mellitus in the elderly patients. Available at http://www.uptodate.com/contents/treatment-of-type-2-diabetes-mellitus-in-the-elderly-patient (Accessed 2011 November 15).
51. Kenreigh CA, Wagner LT. Medication Adherence: A Literature Review. Available at www.mediscape.com/viewarticle/514164 (Accessed 2012 December 27).
52. Lutfey KE, Wishner WJ. Beyond "compliance" is "adherence". Improving the prospect of diabetes care. Diabetes Care. 1999;22(4):635-639.
53. McNabb WL. Adherence in diabetes. Can we define it and can we measure it? Diabetes Care. 1997;20(2):215-218.
54. Haran C. A Passage to insulin: natural progression or failure? Available at www.heathology.com/focus_article.asp?f=diabetes & b=heathology & C= diabetes_insulin (Accessed 2012, February 24).
55. Thompson CJ, Cummings JF, Chalmers J, Gould C, Newton RW. How have patients reacted to the implication of DCCT? Diabetes Care. 1996;19(8):876-879.
56. Adibe MO, Aguwa CN, Ukwe CV, Okonta JM, Udeogaranya PO. Outpatient utilization of antidiabetic drug in the southeastern Nigeria. Int J Drug Dev Res. 2009;1(1):27-36.
57. Yusuff KB, Obe O, Joseph BY. Adherence to antidiabetic drug therapy and self management practices among type 2 diabetes in Nigeria. Pharm World Sci. 2008;30(6):876-883. doi: 10.1007/s11096-008-9243-2
58. Johnson SB: Methodological issues in diabetes research: measuring adherence. Diabetes Care. 1992;15(11):1658-1667.
59. MacLaughlin EJ, Raehl CL, Treadway AK, Sterling TL, Zoller DP, Bond CA. Assessing medication adherence in the elderly: which tools to use in clinical practice? Drugs Aging. 2005;22(3):231-255.
60. Gehi AK, Ali S, Na B, Whooley MA. Self-reported medication adherence and cardiovascular events in patients with stable coronary heart disease: the heart and soul study. Arch Intern Med. 2007;167(16):1798-1803.
2. Fincham JE, Wertheimer AI. Using the health belief model to predict initial drug therapy defaulting. Soc Sci Med. 1985;20(1):101-105.
3. Smith MC. Predicting and detecting noncompliance. In: Social and Behavioural Aspect of Pharmaceutical Care. Smith MC, Wertheimer AI eds. New York, NY: Pharmaceutical Products Press. 1996.
4. World Health Organization. Adherence to long-term therapies: Evidence for action. WHO 2003. Geneva. Switzerland. Available at http://www.who.int/chp/knowledge/publications/adherence_report/en/index.html (Accessed 2012, March 20).
5. Osterberg L, Blaschke T. Adherence to medication. N Engl J Med. 2005;353(5):487-497.
6. Wild S, Roglic G, Green A, Sicree R, King H. Global prevalence of diabetes: estimates for the year 2000 and projections for 2030. Diabetes Care. 2004;27(5):1047-1053.
7. World Health Organization. Prevention of diabetes mellitus. Report of a WHO Study Group. WHO Technical Report series 844, Geneva;WHO:1994.
8. Amos AF, McCarty DJ, Zimmet P. The rising global burden of diabetes and its complication, estimates and projection to the year 2010. Diabet Med. 1997;14(Suppl 5):S1-S85.
9. Unwin N, Sobugivi E, Alberto KGMM. Type 2 diabetes: the challenge of preventing a global epidemic. Diabetes International. 2001;11:4-8.
10. Shams ME, Barakat EA. Measuring the rate of therapeutic adherence among outpatients with type 2 diabetes mellitus in Egypt. Saudi Pharm J. 2010;18(4):225-232. doi: 10.1016/j.jsps.2010.07.004
11. Schechter CB, Walker EA. Improving Adherence to Diabetes Self-management Recommendations. Diabet Spectr. 2002;15(3):170-175. doi: 10.2337/diaspect.15.3.170
12. Vermeire E, Royen PV, Coenen S, Wens J, Denekans J. The adherence of type 2 diabetes patients to their therapeutic regimens: a qualitative study from the patients’ perspective. Pract Diabet Int. 2003;20(6):209-214.
13. Haynes RB, Yao X, Degani A, Kripalani S, Garg A, McDonald HP. Interventions for enhancing medication adherence. Cochrane Database Syst Rev. 2005;(4):CD000011. doi:10.1002/14651858
14. Cramer JA. Relationship between medication compliance and medical outcomes. Am J Health Syst Pharm. 1995;52(14 Suppl 3):S27-S29.
15. Dunbar-Jacob J, Erlen JA, Schlenk EA, Ryan CM, Sereika SM, Doswell WM. Adherence in chronic disease. Annu Rev Nurs Res. 2000;18:48-90.
16. National Pharmaceutical Council. Noncompliance with medical regimens: detection and intervention. Qual Thr Res. 1992;2(3):1-20.
17. Maddigan SL, Feeny DH, Johnson JA. Health related quality of life deficits associated with diabetes and comorbities in a Canadian national population health survey. Qual Life Res. 2005;14(5):1311-1320.
18. Vermeire E, Wens J, Van Royen P, Biot Y, Hearnshaw H, Lindenmeyer A. Interventions for improving adherence to treatment recommendations in people with type 2 diabetes mellitus Cochrane Database Syst Rev. 2005;(2):CD003638.
19. Morgan CL, Currie CJ, Peters JR. Relationship between diabetes and mortality: a population study using record linkage. Diabetes Care. 2000;23(8):1103-1107.
20. Andersson DK, Svärdsudd K. Long-term glycemic control relates to mortality in type 2 diabetes. Diabetes Care. 1995;18(12):1534-43.
21. The Diabetes Control and Complications Trial Research Group. The effect of intensive treatment of diabetes on the development and progression of long-term complications in insulin-dependent diabetes mellitus. N Engl J Med. 1993;329(14):977-986.
22. Lim PC, Lim K. Evaluation of a pharmacist-managed diabetes medication therapy adherence clinic. Pharm Pract. 2010;8(4):250-254.
23. United Kingdom prospective Diabetes Study Group. Intensive blood glucose control with sulfonylurea or insulin compared with conventional treatment and risk of complication in patients with type 2 diabetes (UKPDS 33). Lancet. 1998;352(9131):837-853.
24. Stratton IM, Adler AI, Neil HA, Matthews DR, Manley SE, Cull CA, Hadden D, Turner RC, Holman RR. Association of glycaemia with macrovascular and microvascular complications of type 2 diabetes (UKPDS 35): prospective observational study. BMJ. 2000;321(7258):405-412.
25. Glasgow RE. Compliance to diabetes regimens. Conceptualization, complexity, and determinants. In: Patient Compliance in Medical Practice and Clinical Trials. Cramer JA, Spiker B (eds). Raven Press: New York, NY;1994.
26. Horne R. Adherence to medication: a review of the existing literature. In: Adherence to treatment in medical conditions. Myers LB, Midence K (eds). Harwood Academic Press: Amsterdam; 1998.
27. Blackwell B. Drug therapy. Patient compliance. N Engl J Med. 1973;289(5):249-252.
28. American Diabetes Association. Standards of medical care in diabetes 2006. Diabet Care 2006;29 (Suppl 1):S4-S42.
29. Kroenke K, Pinholt EM. Reducing polypharmacy in the elderly: a controlled trial of physician feedback. J Am Geriatr Soc. 1990;38(1):31-36.
30. Sica DA. Rationale for fixed-dose combinations in the treatment of hypertension: the cycle repeats. Drugs. 2002;62(3):443-462.
31. Bakris GL. The role of combination anti-hypertensive therapy and the progression of renal disease hypertension: looking toward the next millennium. Am J Hypertens. 1998;11(10):158S-162S.
32. Grant RW, Cagliero E, Murphy-Sheehy P, Singer DE, Nathan DM, Meigs JB. Comparison of hyperglycemia, hypertension, and hypercholesterolemia management in patients with type 2 diabetes. Am J Med. 2002;112(8):603-609.
33. Adisa R, Alutundu MB, Fakeye TO. Factors contributing to nonadherence to oral hypoglycemic medication among ambulatory type 2 diabetes patients in southwestern Nigeria. Pharm Pract. 2009;7(3):163-169.
34. Cramer JA. A systematic review of adherence with medications for diabetes. Diabetes Care. 2004;27(5):1218-1224.
35. United Kingdom Prospective Diabetes Study Group. Effect of intensive blood-glucose control with metformin on complications in overweight patients with type 2 diabetes (UKPDS 34). Lancet. 1998;352(9131):854-865.
36. The Creative Research Systems. The complete survey software solution since 1982. Research Aids. Available at http://www.surveysystem.com/sscal.html (Accessed 2011, December 26).
37. Morisky DE, Green LW, Levine DM. Concurrent and predictive validity of a self-reported measure of medication adherence. Med Care. 1986;24(1):67-74.
38. Shalansky SJ, Levy AR, Ignaszewski AP. Self-reported Morisky Score for identifying nonadherence with cardiovascular medications. Ann Pharmacother. 2004;38(9):1363-1368.
39. Vik SA, Maxwell CJ, Hogan DB, Patten SB, Johnson JA, Romonko-Slack L. Assessing medication adherence among older persons in community settings. Can J Clin Pharmacol. 2005;12(1):e152-e164.
40. Fulton MM, Allen ER. Polypharmacy in the elderly: a literature review. J Am Acad Nurse Pract. 2005;17(4):123-132.
41. Fraizer SC. Health outcomes and polypharmacy in elderly individuals: an integrated literature review. J Gerontol Nurs. 2005;31(9):4-11.
42. Bjerrum L, Rosholm JU, Hallas J, Kragstrup J. Methods for estimating the occurrence of polypharmacy by means of a prescription database. Eur J Clin Pharmacol. 1997;53(1):7-11.
43. Grant RW, Devita NG, Singer DE, Meigs JB. Polypharmacy and medication adherence in patients with type 2 diabetes. Diabetes Care. 2003;26(5):1408-1412.
44. Blonde L. Management of type 2 diabetes: update on new pharmacological options. Manag Care. 2000;9(8 Suppl):11-17.
45. Brown AF, Mangione CM, Saliba D, Sarkisian CA; California Healthcare Foundation/American Geriatrics Society Panel on Improving Care for Elders with Diabetes. Guidelines for improving the care of the older person with diabetes mellitus. J Am Geriatr Soc. 2003;51(5 Suppl Guidelines):S265-S280.
46. Bethel MA, Sloan FA, Belsky D, Feinglos MN. Longitudinal incidence and prevalence of adverse outcomes of diabetes mellitus in elderly patients. Arch Intern Med. 2007;167(9):921-927.
47. Patel I, Chang J, Shenolikar RA, Balkrishman R. Medication adherence in low income elderly type 2 diabetes patients: a retrospective cohort study. Int J Diabet Mellit. 2010;2(2):122-124.
48. Knowler WC, Barrett-Connor E, Fowler SE, Hamman RF, Lachin JM, Walker EA, Nathan DM; Diabetes Prevention Program Research Group. Reduction in the incidence of type 2 diabetes with lifestyle intervention or metformin. N Engl J Med. 2002;346(6):393-403.
49. Wing RR, Hamman RF, Bray GA, Delahanty L, Edelstein SL, Hill JO, Horton ES, Hoskin MA, Kriska A, Lachin J, Mayer-Davis EJ, Pi-Sunyer X, Regensteiner JG, Venditti B, Wylie-Rosett J; Diabetes Prevention Program Research Group. Achieving weight and activity goals among diabetes prevention program lifestyle participants. Obes Res. 2004;12(9):1426-1434.
50. McCulloch DK, Munshi M. Treatment of type 2 diabetes mellitus in the elderly patients. Available at http://www.uptodate.com/contents/treatment-of-type-2-diabetes-mellitus-in-the-elderly-patient (Accessed 2011 November 15).
51. Kenreigh CA, Wagner LT. Medication Adherence: A Literature Review. Available at www.mediscape.com/viewarticle/514164 (Accessed 2012 December 27).
52. Lutfey KE, Wishner WJ. Beyond "compliance" is "adherence". Improving the prospect of diabetes care. Diabetes Care. 1999;22(4):635-639.
53. McNabb WL. Adherence in diabetes. Can we define it and can we measure it? Diabetes Care. 1997;20(2):215-218.
54. Haran C. A Passage to insulin: natural progression or failure? Available at www.heathology.com/focus_article.asp?f=diabetes & b=heathology & C= diabetes_insulin (Accessed 2012, February 24).
55. Thompson CJ, Cummings JF, Chalmers J, Gould C, Newton RW. How have patients reacted to the implication of DCCT? Diabetes Care. 1996;19(8):876-879.
56. Adibe MO, Aguwa CN, Ukwe CV, Okonta JM, Udeogaranya PO. Outpatient utilization of antidiabetic drug in the southeastern Nigeria. Int J Drug Dev Res. 2009;1(1):27-36.
57. Yusuff KB, Obe O, Joseph BY. Adherence to antidiabetic drug therapy and self management practices among type 2 diabetes in Nigeria. Pharm World Sci. 2008;30(6):876-883. doi: 10.1007/s11096-008-9243-2
58. Johnson SB: Methodological issues in diabetes research: measuring adherence. Diabetes Care. 1992;15(11):1658-1667.
59. MacLaughlin EJ, Raehl CL, Treadway AK, Sterling TL, Zoller DP, Bond CA. Assessing medication adherence in the elderly: which tools to use in clinical practice? Drugs Aging. 2005;22(3):231-255.
60. Gehi AK, Ali S, Na B, Whooley MA. Self-reported medication adherence and cardiovascular events in patients with stable coronary heart disease: the heart and soul study. Arch Intern Med. 2007;167(16):1798-1803.