|ISSN No. 1606-7754 Vol.16 No.2 August 2008|
Risk factors of poor control of HBA1c and diabetic retinopathy: Paradox with insulin therapy and high values of HDL in African diabetic patients
B Longo-Mbenza,1 MM Muaka,2 G Mbenza,3 S Mbungu-Fuele,4 L Mabwa-Mbalanda,4 V Nzuzi- Babeki,4 J Mbadi-A-Sungu4
Division of Cardiology, Pathophysiology and Clinical Epidemiology1; University of Kinshasa; Division of Ophthalmology2, Army Salvation Hospital, Kinshasa, Gombe3;Lomo Medical Center, Kinshasa, Limete,4 DRC
Objective: To determine the risk factors of poor control of glycated haemoglobin and diabetic retinopathy. The agreement between poor control of glycated haemoglobin (HbA1c) >7% and poor control of glycemia ≥ 126 mg/dL to classify diabetic retinopathy was also assessed. Design, settings and methods: The study was a cross-sectional survey carried out on 300 African diabetic patients admitted to Lomo Medical Center, Kinshasa, Congo, between July 2005 and December 2007. Patients (150 type 1 and 151 type 2) were interviewed and underwent a complete medical assessment. HbA1c levels, anthropometry, blood pressure components, lipid profile, type of diabetes, severity and complications were determined for each patient. All patients were examined for evidence and severity of diabetic retinopathy by an ophthalmologist. Results: The rates of arterial hypertension, uncontrolled hypertension, poor control of HbA1c, poor control of glycemia, higher pulse pressure and diabetic retinopathy were 73.3%, 81.8%, 68%, 57%, 47.7% and 33.3%, respectively. Type 1 diabetes, diabetes duration ≥ 4 years, female sex, underweight, diabetic retinopathy, diabetic nephropathy, elevated total cholesterol and higher levels of HDL-cholesterol were significantly associated with poor control of HbA1c. There was a poor agreement of 52% and kappa statistic of 0.19 (p<0.0001) between poor control of HbA1c and poor glycemic control to classify diabetic retinopathy. In all diabetic patients, aged ≥60 years, female sex, diabetes duration ≥4 years, type 1 diabetes, higher pulse pressure, underweight, poor control of HbA1c, smoking, stroke, diabetic nephropathy and low HDL-cholesterol are significantly associated with the presence and the severity of diabetic retinopathy. However, in 87 diabetic patients with a history of intravenously administered insulin, duration diabetes ≥ 4 years and good control of HbA1c <7% are significantly associated with the presence of diabetic retinopathy. There was a J-shaped relationship between poor control of glycemia ≥126mg/dL and the severity of non proliferative diabetic retinopathy. Conclusion: Urgent and efficient diabetes care and diabetes monitoring are needed in sub-Saharan Africa.
Keywords: Africa, diabetes mellitus, glycated haemoglobin, diabetic retinopathy, risk factors
Sub-Saharan Africa (SSA) now faces a double disease burden, with emerging non communicable diseases (NCD), such as arterial hypertension, stroke, coronary heart disease and diabetes mellitus (DM) added to the challenges in infectious diseases.1 In a survey conducted in 2005 in SSA, it is estimated that 16% people had DM.2,3
The escalating prevalence of type 1 and type 2 DM, risk factors and chronic complications of DM are now established. These include 7-52% for diabetic retinopathy (DR), 6-30% for diabetic nephropathy (DN), and 1-5% for macroangiopathy.4,5 DR, DN, chronic renal failure, neuropathy, age ≥ 60 years, smoking, DM duration ≥ 4years and higher pulse pressure are identified risk factors of stroke in diabetic Africans,6 whereas higher pulse pressure is a risk factor of diabetic cardiomyopathy7 and DR8 in Africans, respectively. Ethnic differences in the prevalence and severity of DM chronic complications9 and low lipid profiles or indifferent role of dyslipidemia in the general population10 or in NCD including DM11, 12 are reported from SSA. Although genetic susceptibility may not be ruled out, lack of health care facilities to control of blood glucose, blood pressure and dyslipidemia might account for most of the differences with other populations around the world.
Lack of awareness by Africans and facilities for detection and monitoring of DM may contribute to the high prevalence of diabetic complications.13 The high cost of insulin is the most important cause of lack of access to insulin in type 1 diabetics.14 Moreover, a small percentage of type 2 diabetics require insulin when they become severely underweight and hyperglycaemic. There is, therefore, an urgent need for intravenous insulin (5-10 UI of Insulin per hour) to control hyperglycemia in these poorly controlled African diabetic patients. In the Democratic Republic of the Congo (DRC), our country, where people with type 1 DM have access to insulin for less than 25% of the time,14 the only equipment for continuous monitoring of glycated haemoglobin (HbA1c) in diabetics had been introduced in July 13th, 2005 in our LOMO MEDICAL Clinic, Kinshasa, Limete.
Data from the United Kingdom Prospective Diabetes study (UKPDS)15 and the Diabetes control and complication trial (DCCT)16 have shown that intensive control of glucose results in a 25-70% reduction in the number and severity of DM microvascular complications. In the UKPDS, control of high blood pressure (BP) reduced the risk of microvascular complications by 37% and death from type 2 DM-related disease by 32%.17 Greater reductions from those with tight blood glucose control were observed. Furthermore, compared with diet/oral antidiabetic drugs regimen, insulin treatment conferred higher risk of DR in all Congolese diabetics (OR=2 95%CI 1.2-3.5; P<0.01) in general and in female diabetics (OR=2.7 95%CI 1.4-5.4 P<0.01) and type 2 diabetics (OR=2.4 95%CI 1.4-4.1; P<0.001) in particular.8 Because the lack of data on HbA1c among Congolese diabetics, the present study was initiated with the aim of determining the association between cardiovascular disease (CVD) risk factors, nutritional status, DM duration, diabetic chronic complications with special reference to DR, insulin treatment and HbA1c. The lipid and non lipid risk factors to DM complications were also assessed.