ORIGINAL ARTICLE

Pdf version

RISK FACTORS FOR DIABETIC RETINOPATHY IN DIABETICS SCREENED USING FUNDUS PHOTOGRAPHY AT A PRIMARY HEALTH CARE SETTING IN EAST MALAYSIA

Table 3: Adjusted¹ Odds Ratio for Factors associated with diabetic retinopathy

¹Each odds ratio is adjusted for all other variables in the table

DISCUSSION

As about 20% of the patients were Sarawak native (Bidayuh, Iban and other natives) of which very little data were available for this ethnic group, our study found that the prevalence of retinopathy of the native were comparable to the other ethnic group.

The proportion of patients with DR in our study was 23.7%. This was much lower than the prevalence found in other hospital based studies^11,12 and some community base studies^20-22 in Malaysia, where DR were detected in 31-50% of the patients studied. This could be due to our study reported findings from a primary health care centre where fundus photography was done for screening of asymptomatic patients with diabetes. This group of patients might have less complication as patients with complications might have been referred to referral centres in hospitals. This figure was comparable with the prevalence range of 10.5-26.2% found in other population based studies in India and United Kingdom,^23-25 but it is lower compared to other community based studies in Singapore and China.^26-27 The Singapore study²⁶ were on patients being referred from the primary health care centres to the hospital, this group of patients may have been screened earlier before being referred, so the possibility of DR is higher. Secondly, the differences of the racial composition in these studies^26,27 where majority were Chinese whereas in our study, there were almost equal combination of Chinese, Malay and native, may have contributed to the differences. Although it was not statistically significant, the proportion of natives found to have DR were lower in our study. Further study is needed to explore these differences. NPDR was the commonest form of DR seen in our study which is consistent with other studies.^25-28

Previous studies had found that patients with a longer duration of diabetes has a higher risk of developing DR.^26-27,29-34 We also found association between the duration of DM and the presence of DR. The odds of developing DR was 2.5 times higher for a patient with duration of diagnosis between five to 10 years when compared to a patients with <5 years of diabetes and the odds of developing DR increased 1.2 to 1.9 times with each increase of five years. Another local study¹² and studies from Singapore, Thailand and China found similar trend in association of duration of DM with the risk of developing DR.^26,27,34 However, Thailand’s study³⁴ shown much lower odds ratio of DR development at the similar interval of disease duration. Better control of diabetes among patients in tertiary centres in the Thailand study³⁴ may be the contributing factor for the differences.

We found an inverse relationship between BMI and DR. Patients with lower BMI were more likely compared to obese and overweight to develop DR. Similar inverse relationship was reported in other studies in India.^23,35 However, the association of BMI and DR has not been consistently demonstrated in all studies. Study in China found no significant association of BMI and DR.²⁷ In some studies conducted in developed countries, higher BMI is associated with DR subjects with T2DM.^36,37

Visual loss was associated with higher risk of DR in our study. Study in India also showed higher percentage of moderate to severe visual loss among patients with PDR.²⁸

In our study, the control of systemic hypertension and separate analysis of systolic and diastolic BP was found not significantly associated with the presence of DR in the multivariate analysis. This is inconsistent with another local hospital base study where hypertension were reported to be associated with higher risk of DR.¹² The low proportion of patients with BP at >140/90 mmHg (35.5%) in this study may have contributed to the differences in our findings.

Other studies found association of renal impairment, cardiovascular diseases and anaemia with DR.^5-7 The small number of patients reported with these risk factors from our study could have contributed to the negative findings.

Other studies reported higher HbA_1c levels positively associated with NPDR, PDR and macular oedema.^29,30 The disproportionately low numbers of patients with optimal HbA_1c may have contributed to the insignificant association of HbA_1c to the presence of DR in this study. Serum lipids have been found inconsistently associated with DR in various studies.^38-41 Although majority of our patients had dyslipidemia, but we could not find any significant association of serum lipids with DR. The negative findings of this association found from our study add further evidence to the inconsistency of this association.

There were some limitations in our study. Firstly, the cross-sectional nature of the study cannot provide temporal information for the significant associations reported. Secondly, we did not have the information of the blood glucose level in our patients. Thirdly, socio economic and psychosocial factors, health care access and utilisation factors which was not assessed in this study, may modified the relationship between the known risk factors and risk of having DR.⁴² Fourthly, our fundus photography included only the standard 2-fields out of the standard 7-fields. These could have underestimated the actual prevalence of DR. Finally, the relatively small number of people with proliferative DR and macular oedema limits our ability to assess associations with these subtypes of DR.

In summary, this study provides data on risk factors associated with DR in a mixed ethnic population including native in Borneo Islands at a primary health care setting. We confirm associations of DR with diabetic duration, BMI and visual loss. Our data provide preliminary findings to help to improve the preventive strategies at the primary health care setting. Ideally, according to the guideline,¹⁶ all patients with diabetes should have screening fundus examination done at least once a year. However, data from the latest National Health Survey found that more than half of patients with known DM had never undergone an eye examination.⁴³ In the constraint of time and facilities, a selection of patients with higher risk factors like longer duration of disease, lower BMI and those who had moderate visual loss for priority of earlier screening may be a better strategy to enable the detection of patients with DR earlier.

ACKNOWLEDGEMENT

The authors would like to thank the staffs of KKJM, and SN Asmarlina binti Che Aris for their assistance and support in conducting the study. We would also like to acknowledge the Director General of Health of Malaysia, the Department of Health, Ministry of Health, Sarawak, Malaysia and Universiti Malaysia Sarawak. We would also like to extend our thanks to Prof KG Rampal for his statistical guidance.

REFERENCES

1. Wild S, Roglic G, Green A, et al. Global prevalence of diabetes: estimates for the year 2000 and projections for 2030. Diabetes Care. 2004;27(5):1047-53. [PubMed] [Full text]
2. King H, Aubert RE, Herman WH. Global burden of diabetes, 1995-2025: prevalence, numerical estimates, and projections. Diabetes Care. 1998;21(9):1414-31. [PubMed]
3. National Institute of Health Malaysia. The Third National Health and Morbidity Survey (NHMS III). 2006.
4. Klein R, Klien BE. Vision disorders in diabetes. In: Harris MI, Catherine CC, Stern MP, et al. editors. Diabetes in America. 2nd ed. National Diabetes Data Group, National Institute of Health, National Institute of Diabetes and Digestive and Kidney Disease. Bethesda: The National Diabetes Information Clearinghouse (NDIC); 1995. p. 293-338.
5. Dowse GK, Humphrey AR, Collins VR, et al. Prevalence and risk factors for diabetic retinopathy in the multiethnic population of Mauritius. Am J Epidemiol. 1998;147(5):448-57. [PubMed] [Full text]
6. Ranil PK, Raman R, Rachepalli SR, et al. Anemia and diabetic retinopathy in type 2 diabetes mellitus. J Assoc Physicians India. 2010;58:91-4. [PubMed]
7. Chew EY, Mills JL, Metzger BE, et al. Metabolic control and progression of retinopathy. The Diabetes in Early Pregnancy Study. National Institute of Child Health and Human Development Diabetes in Early Pregnancy Study. Diabetes Care. 1995; 18(5):631-7. [PubMed]
8. Klein R, Klein BE, Moss SE. Visual impairment in diabetes. Ophthalmology. 1984;91(1):1-9. [PubMed]
9. Goh PP, National Eye Database Study Group. Status of diabetic retinopathy among diabetics registered to the Diabetic Eye Registry, National Eye Database, 2007. Med J Malaysia. 2008;63 Suppl C:24-8. [PubMed]
10. Wan Nazaimoon WM, Letchuman R, Noraini N, et al. Systolic hypertension and duration of diabetes mellitus are important determinants of retinopathy and microalbuminuria in young diabetics. Diabetes Res Clin Pract. 1999;46(3):213-21. [PubMed]
11. Shriwas SR, Rahman Isa AB, Reddy SC, et al. Risk factors for retinopathy in diabetes mellitus in Kelantan, Malaysia. Med J Malaysia. 1996;51(4):447-52. [PubMed]
12. Tajunisah I, Nabilah H, Reddy SC. Prevalence and risk factors for diabetic retinopathy - a study of 217 patients from University of Malaya Medical Centre. Med J Malaysia. 2006;61(4):451-6. [PubMed]
13. The Official Portal of the Sarawak Government. About Sarawak. [Online] [Link]
14. Practise Guidelines for Diabetes Mellitus Type 2 (NIDDM). The Malaysian Consensus 2000. Kuala Lumpur: Ministry of Health Malaysia.
15. Asian-Pacific Type 2 Diabetes Policy Group. Type 2 Diabetes. Practical Targets and Treatment. 3rd ed. 2002. [Full text]
16. Ministry of Health Malaysia. Clinical Practice Guidelines. Management of Type 2 Diabetes Mellitus, 3rd ed. 2004. [Full text]
17. Academy of Medicine of Malaysia. Clinical Practice Guidelines on Management of Obesity. 2004. [Full text]
18. American Academy of Ophthalmology. International Clinical Diabetic Retinopathy Disease Severity Scale. 2002. [Online][Full text]
19. American Academy of Ophthalmology. International Clinical Diabetic Macular Edema Disease Severity Scale. 2002. [Online][Full text]
20. Haireen AH, Khoo EM. A comparison study between direct ophthalmoscopy and fundus camera in detecting diabetic retinopathy. Wonca Asia-Pacific Regional Conference; 4-7 June 2009; Hong Kong.
21. Keah SH, Chng KS. Prevalence of diabetic retinopathy in a primary care setting using digital retinal imaging technology. Malaysian Family Physician. 2006;1(1):19-22. [Full text]
22. Yang YF, Chong HH, Yang YK. Diabetic retinopathy in the community. Med J Malaysia. 2001;56(1):104-5. [PubMed]
23. Narendran V, John RK, Raghuram A, et al. Diabetic retinopathy among self reported diabetics in southern India: a population based assessment. Br J Ophthalmol. 2002;86(9):1014-8. [PubMed] [Full text]
24. Dandona L, Dandona R, Naduvilath TJ, et al. Population based assessment of diabetic retinopathy in an urban population in southern India. Br J Ophthalmol. 1999;83(8):937-40. [PubMed] [Full text]
25. Younis N, Broadbent DM, Harding SP, et al. Prevalence of diabetic eye disease in patients entering a systematic primary care-based eye screening programme. Diabet Med. 2002;19(12):1014-21. [PubMed]
26. Lim MC, Lee SY, Cheng BC, et al. Diabetic retinopathy in diabetics referred to a tertiary centre from a nationwide screening programme. Ann Acad Med Singapore. 2008;37(9):753-9. [PubMed] [Full text]
27. Wang FH, Liang YB, Peng XY, et al.Risk factors for diabetic retinopathy in a rural Chinese population with type 2 diabetes: the Handan Eye Study. Acta Ophthalmol. 2011;89(4):e336-43. [PubMed]
28. Namperumalsamy P, Kim R, Vignesh TP, et al. Prevalence and risk factors for diabetic retinopathy: a population-based assessment from Theni District, south India. Br J Ophthalmol. 2009;93(4):429-34. [PubMed]
29. Klein R, Klein BE, Moss SE, et al. The Wisconsin Epidemiologic Study of Diabetic Retinopathy. VII. Diabetic nonproliferative retinal lesions. Ophthalmology. 1987;94(11):1389-400. [PubMed]
30. Klein R, Klein BE, Moss SE, et al. The Wisconsin epidemiologic study of diabetic retinopathy. IV. Diabetic macular edema. Ophthalmology. 1984;91(12):1464-74. [PubMed]
31. Sparrow JM, McLeod BK, Smith TD, et al. The prevalence of diabetic retinopathy and maculopathy and their risk factors in the non-insulin-treated diabetic patients of an English town. Eye (Lond). 1993;7(Pt 1):158-63. [PubMed]
32. Tapp RJ, Shaw JE, Harper CA, et al. The prevalence of and factors associated with diabetic retinopathy in the Australian population. Diabetes Care. 2003;26(6):1731-7. [PubMed] [Full text]
33. The effect of intensive treatment of diabetes on the development and progression of long-term complications in insulin-dependent diabetes mellitus. The Diabetes Control and Complications Trial Research Group. N Engl J Med. 1993;329(14):977-86. [PubMed] [Full text]
34. Chetthakul T, Deerochanawong C, Suwanwalaikorn S, et al. Thailand diabetes registry project: prevalence of diabetic retinopathy and associated factors in type 2 diabetes mellitus. J Med Assoc Thai. 2006;89 Suppl 1:S27-36. [PubMed]
35. Rani PK, Raman R, Chandrakantan A, et al. Risk factors for diabetic retinopathy in self-reported rural population with diabetes. J Postgrad Med. 2009;55(2):92-6. [PubMed]
36. Effect of intensive blood-glucose control with metformin on complications in overweight patients with type 2 diabetes (UKPDS 34). UK Prospective Diabetes Study (UKPDS) Group. Lancet. 1998;352(9131):854-65. [PubMed]
37. van Leiden HA, Dekker JM, Moll AC, et al. Blood pressure, lipids, and obesity are associated with retinopathy: the hoorn study. Diabetes Care. 2002;25(8):1320-5. [PubMed] [Full text]
38. Klein BE, Moss SE, Klein R, et al. The Wisconsin Epidemiologic Study of Diabetic Retinopathy. XIII. Relationship of serum cholesterol to retinopathy and hard exudate. Ophthalmology. 1991;98(8):1261-5. [PubMed]
39. Lloyd CE, Klein R, Maser RE, et al. The progression of retinopathy over 2 years: the Pittsburgh Epidemiology of Diabetes Complications (EDC) Study. J Diabetes Complications. 1995;9(3):140-8. [PubMed]
40. Sjolie AK, Stephenson J, Aldington S, et al. Retinopathy and vision loss in insulin-dependent diabetes in Europe. The EURODIAB IDDM Complications Study. Ophthalmology. 1997;104(2):252-60. [PubMed]
41. Chew EY, Klein ML, Ferris FL 3rd, et al. Association of elevated serum lipid levels with retinal hard exudate in diabetic retinopathy. Early Treatment Diabetic Retinopathy Study (ETDRS) Report 22. Arch Ophthalmol. 1996;114(9):1079-84.[PubMed]
42. Varma R. Diabetic retinopathy: challenges and future directions. Am J Ophthalmol. 2006;141(3):539-41. [PubMed]
43. Goh PP, Omar MA, Yusoff AF. Diabetic eye screening in Malaysia: findings from the National Health and Morbidity Survey 2006. Singapore Med J. 2010;51(8):631-4. [PubMed] [Full text]