Demographics and lifestyles
The patients in the well-controlled and in the inadequately-controlled diabetic groups were similar in terms of age distribution, gender, smoking status, family history of early-onset myocardial infarction and family history of diabetes. Subjects in the inadequately-controlled diabetic group were less likely to do regular physical exercise (62.8% vs. 76.2%, P=0.002) and more likely to have daily alcohol consumption (7.2% vs. 3.2%, P=0.041) than those in the well-controlled glycaemic group (as shown in Table 2). However, as shown in Table 3, the multivariate logistic regression model analysis showed that only regular physical exercise (> 3 times/week) was independent factor negatively related to inadequately glycaemic control (OR: 0.523, 95% confidence interval (CI): 0.318-0.860).
Clinical characteristics including systolic and diastolic blood pressure, HDL-cholesterol and overt diabetic complications were similar in the well-controlled and the inadequately-controlled diabetic groups. However, as shown in Table 2, the subjects in the inadequately-controlled diabetic group were more likely to have BMI ≥ 24.0 kg/m2 (61.8% vs. 48.0%; P=0.003), disease duration of >10 years (29.5% vs. 18.5%, P <0.001), LDL-cholesterol level ≥3.12 mmol/L (75.8% vs. 62.1%, P=0.002), triglycerides level ≥1.70 mmol/L (77.8% vs. 59.3%, P <0.001) and lower level of HOMA-β (27.8 vs. 51.9, P <0.001). In the multivariate logistic regression model analysis, BMI ≥ 24.0 kg/m2 (OR: 3.234, 95% CI: 1.972-5.305), longer disease duration (5-10 years vs. ≤ 5 years, OR: 1.488, 95% CI: 0.849-2.609; > 10 years vs. ≤5 years, OR: 3.066, 95% CI: 1.735-5.427) and triglycerides level ≥1.70 mmol/L (OR: 2.633, 95% CI: 1.584-4.377) were independent factors positively related to inadequate glycaemic control; whereas, higher level of HOMA-β (OR: 0.219, 95% CI: 0.149-0.320) negatively related to inadequate glycaemic control as shown in Table 3.
Treatment strategies and hypoglycemic experience
The therapeutic approach was left to the discretion of the attending physician. In this cohort, patients received OAD alone to control hyperglycaemia. Of the 455 patients, 149 (32.8%) received monotherapy of OAD, 211 (48.8%) patients were treated with dual-OAD therapy, and 78 (18.4%) with ≥triple-OAD therapy. In particular, sulfonylureas/glinides combined with metformin were the most common type of combination therapy (25.9%). There was no statistical difference in the number of OAD between the inadequately-controlled diabetic group and the well-controlled glyaemic group. Likewise, there was no significant difference between the two groups with regard to concomitant medications of angiotensinconverting enzyme inhibitors/angiotensin receptor inhibitors, calcium antagonist, statins or fibrates. However, subjects in the inadequately-controlled diabetic group were more likely not to visit medical practitioners regularly (< once/month, 38.2% vs. 24.2%, P=0.004) during the past 6 months before the index visit (Table 2). In the multivariate logistic regression model analysis, regular medical visit was related to optimal glycaemic control (once or twice/month vs. <once/month, OR: 0.473, 95% CI: 0.267-0.839; >twice/month vs. <once/month, OR: 0.523, 95% CI: 0.303-0.904). In addition, subjects in the inadequately-controlled diabetic group had less hypoglycemic event and less fear of hypoglycemia, compared with those with ideal glycemic control. In the multivariate logistic regression model analysis, the HFS scores were negatively related to the poor glycemic outcome (0-8 vs. ≤0, OR: 0.707, 95% CI: 0.406-1.231; >8 vs. ≤0, OR: 0.444, 95% CI: 0.260-0.759).
Principal axis factor analysis with varimax rotation was conducted to assess disease duration, TG, BMI, HOMA-β and HFS-II scores, which was continuous variants and statistic significant in the multiple linear regression. We identified two dominant factors that explained 52.64% of the total variance of data. After rotation, the first and the second factors accounted for 31.22% and 21.42% of the variance, respectively (Table 4). In the first factor, called lipid factor, BMI and triglycerides had positive loading. In the second factor, called mental health factor (HFS-II scores) had positive loading.
This Chinese cohort of 455 outpatients with T2DM showed that nearly a half (45.5%) of the subjects had inadequate glycaemic control (HbA1c level ≥ 6.5%), with mean HbA1c level of 6.7%. Univariate analysis indicated that alcohol addiction, physical inactivity, longer disease duration, higher BMI, lower HOMA-β index, less frequency of medical visit, worse lipid profiles (LDL-cholesterol, triglycerides) were significantly associated with inadequate glycaemic control. However, disease duration, BMI, HOMA-β, plasma triglyceride level, frequency of medical visit, physical activity and HFS score were found to be the independent determinants of glycaemic control using a multivariate logistic regression analysis. There were more chance of hypoglycemia and more psychological worry of hypoglycemia in the group on target of HbA1c level less than 6.5%.
Sample and representative of the population
The present study reflected the current real-world outcomes of a group of outpatients with mild-to-moderate T2DM with shorter disease duration and taking OAD only, who were from a selection of high-ranking university or municipal hospital-based settings in the most economically advanced metropolises in this country, and under the specialists’ care for at least 6 months, and showed the overwhole optimistic outcome of the average HbA1c level of 6.7%. Our results extended previous evidence showing continuous improvement of diabetes control during the past decade in China.21 However, since the study was not designed to be representative of all Chinese patients with T2DM, the results should not be extrapolated into all patients with T2DM in China. The Diabcare-China surveys which enrolled 2246 diabetic patients with mean age of 59.7 years and mean diabetes duration of 8.7 years in 30 urban hospitals in 2006 showed that only 11.5% of the subjects obtained optimal glycaemic control defined as HbA1c level <6.5%, with mean HbA1c of 7.6%. In the Diabcare-China surveys, the subjects were those with longer duration (8.7 years); of whom 37% were treated with insulin and 5% were Type 1 diabetes. It has been shown that insulin requirement was also a factor of disease severity and was a predictor of poor glycaemic control.12 The discrepancy of the outcome of glycaemic control in the two Chinese studies was mainly ascribed to differences of the enrolled subjects. Surveys for a panoramic overview of the status of diabetes care in China should be performed based on large-scale cross-sectional population-based epidemiological study on a stratified randomly selected sample, including diabetic patients from remote rural areas, who are in lower socioeconomic status, poor access/quality of medical care and lack of basic knowledge on diabetes.
Possible causes of inadequate glycaemic control and clinical implications
As for the effects of OAD in real-life medical practice, these results showed that even in the most economically developed cities in China, and with the efforts for at least six months by the specialists who had been equipped with the updated knowledge and skills on diabetes, there were still a half of patients who were not able to achieve optimal glycaemic control recommended by the international guidelines. We sought to explore barriers to inadequate glycaemic control, which may provide clues for future clinical improvements of diabetes care.
First of all, an association between longer disease duration and inadequate glycaemic control has been found in our study, which is in accordance with many previous studies.9,11,12 The fact that the longer someone had been diagnosed with diabetes, the harder it was to maintain glycaemic control highlighted the inevitable progressive β-cell failure. We observed that overweight and low HOMA-β were related to inadequate glucose control. It could be inferred that the primary defects of peripheral insulin resistance and impaired insulin secretion may be involved in the process of diabetes and determine its outcomes. The progressive β-cell failure undermines the long-term effectiveness of most OAD therapies. Findings from the UKPDS indicated that about a half of the patients failed to response to sulfonylureas therapy alone by the 6th year.22 In a prospective, population-based study using retrospective observational data, Brown et al23 found that the average patient accumulated nearly 10 years of excess glycaemia burden of HbA1c >7.0% from diagnosis until the initiation of insulin therapy. Early initiation of insulin treatment can compensate for the decline in β-cell function and stop the vicious cycle of glucotoxicity to β-cell, resulting in long-term outcome improvement in patients with T2DM. In this study, 18.4% of subjects with HbA1c >6.5% received combination therapy of triple- or quadruple-OAD who should be supposed to receive insulin treatment earlier. The relation between higher BMI and inadequate glycaemic control may also reflect the adverse effects of many OAD therapies, especially high-dose sulfonylureas; as well as general indifference of weight control in our real-life practice of diabetes management. Therefore, the results reinforces the recommendation of meformin as the first-choice drug in the treatment of T2DM by many guidelines. And we can anticipate that both glucagon-like peptide type 1 (GLP-1) receptor agonists and dipeptidyl peptidase 4 inhibitor will be encouraging, exp. in both weigh control and long-term glycaemic outcome.24
In our study, 68.1% of the subjects with HbA1c ≥6.5% were <8%. We have not observed any particular OAD therapeutic option was superior to another regimen. From the view that the relative contribution of postprandial blood glucose excursions is predominant in fairly controlled patients,25 we may deduce the contribution of postpranial blood glucose in these poorly-controled subjects. Only when both fasting and postprandial blood glucose achieve their targets can the patients approach their HbA1c goal of <7%. A prospective study of intensive glucose control therapy among 164 patients with a baseline HbA1c ≥ 7.5% lends support to this concept.26 In that study, therapy was first targeted at fasting blood glucose of <5.6 mmol/L and then postprandial blood glucose of <7.8 mmol/L. Of patients who achieved the fasting target, 64% had HbA1c ≤7%; of patients who achieved both fasting and postprandial plasma glucose targets, 94% reached this HbA1c goal. Therefore, monitoring blood glucose including postprandial status and adjustment of the OAD with those targeting postprandial glucose excursions will provide extra benefits for improvement of diabetes outcome in these outpatients.
In addition to add-on therapy with other OAD and/or insulin, other non-pharmacologic approaches to improve glycaemic control, such as enduring physical activity and ability in diabetes self-management, should be motivated. The present study indicated that subjects with scheduled exercises of > 3 times a week were proved to be in better glycaemic control. An observational study of 3042 adults from Greece found that increased level of physical activity may partly ameliorate the detrimental effects of overweight and obesity on insulin sensitivity; and interestingly, overweight or obese subjects but physically active had lower level of fasting insulin levels than lean, inactive individuals.27 It is well recognized that regular exercise has positive benefits through improvements in blood pressure, weigh control, insulin sensitivity, and plasma lipid profiles. Furthermore, exercise is also cost-effective, which is evidently important in China, as the extent of medical insurance coverage is still limited in this largest developing country. Barriers to regular exercise in China, in general, lie in various aspects, including the lack of effective and motivated educational programs, monitoring system, and operational guidelines in diabetes education; difficult assess to exercise facilities; and the ignorance or inertia of patients etc. Further diabetes education focusing on alerting the importance and improving the feasibility of physical activity should be reinforced.
The most intriguing finding in the present study is the association of hypertriglyceridaemia and inadequate glycaemic control. Although the intertwined and complex relationship linking diabetes and hypertriglyceridemia could not be explored by this study, we hypothesized that the increase in triglycerides may be due to insulin resistance and relative insulin deficiency which results in faulty glucose utilization, and causes hyperglycemia and mobilization of fatty acids from peripheral adipose tissue. The excess fatty acids are both mobilized for energy purpose and accumulated in the liver, which are converted to triglycerides. This phenomenon might be more evident for the Chinese population characterized by the carbohydrate-rich food. It has been demonstrated that the high plasma level of free fatty acids was related with excessive accumulation of fat in pancreatic β-cells,28 and it leads to constellation of islet derangements, including the decrease in β-cell GLUT-2 expression, enhancement of nitric oxide formation, impairment of β-cell function and apoptosis of a substantial subgroup of β-cells.29 These mechanistic studies can explain, at least in part, the association between hypertriglyceridaemia and inadequate glycaemic control. Furthermore, the accumulating evidence has shown that TG levels predicts CVD risk independently. For example, 29 studies including two separate case-control prospective cohorts from the Reykjavik and EPIC-Norfolk studies and 27 additional prospective studies, consistently indicate significant association between hypertriglycemia and the coronary heart disease risk (OR: 1.72, 95% CI: 1.56, 1.90).30 Recently, the ACCORD LIPID study has strengthen the benefits of adding fenofibrate to basic statin therapy in type 2 diabetes with elevated serum levels of triglycerides (2.3 mmol/L or higher).31 But the therapy of dyslipidaemic type 2 diabetic patients is dilatory in the real-life diabetic care in China. The common approach to the management of hypertriglyceridaemia in the setting of T2DM is to pursue aggressive lowering of plasma glucose prior to the initiation of any triglyceride-lowering drugs.32,33 In this study, the majority of patients had never received any lipid-lowering strategies, despite the fact that early initiation of lipid-lowering therapy may get additional benefits in both glycaemic control and reduced CHD risk.34
Finally, even though all the included patients were treated OAD only, symptoms of hypoglycaemia were common and reported by nearly 41.4% of all subjects, in line with the VADT study35 and previous RECAP-DM study in Europe.9 In the group of subjects with HbA1c ≤6.5%, there is higher incidence of self-reported hypoglycemic experience and higher HFS score. Both multivariate logistic regression model and factor analysis (Table 4) had confirmed the association of glycemia control and greater fear of hypoglycemia. The result reminded us the risk of hypoglymia of the intensive glycemic control and iatrogenic hypoglycemia as the limiting factor in the glycemic management of diabetes as well. Whether every subjects in group of HbA1c ≤6.5% is suitable or not needs further consideration, esp. those with recurrent hypoglycemia and severe hypoglycemia. Our challenge is seeking ways not only to lower blood glucose to near-normal values to lower the risk for long-term complications, but also at the same time to minimize hypoglycemia-associated morbidity and mortality. For a medical doctors or nurses, carefully question the patient at each visit to probe for details of episodes that the patient recognized as being caused by hypoglycemia, but also to assess whether the patient has experienced events that went unrecognized—in particular, neurologic symptoms that required the assistance of a family member but were not identified as severe hypoglycemia, and then to set an particular goal of blood control for each patient. In addition, detailed educations for the patient about symptoms and treatment of hypoglycemia will allay the fear of hypoglycemia and increase the adherence.
Strength and limitations
As mentioned elsewhere,9 potential limitations of the REACP-DM study related to physician and patient selection, the observational nature of the study. The fact that the study involved a relatively small, non-probability-based sample of physicians and patients did not allow us to rule out selection bias. It is conceivable that physicians whose patients were overall less ill and more likely to achieve HbA1c goals may have been more motivated to participate in a study assessing HbA1c goal achievement in their practices. It is particularly worth mentioning that the study came from multi-centres from relatively developed areas in China, where access to medical counseling and various treatment modalities are easy to approach. Under these circumstances, it was very likely that rate of adequate glycaemic control in the study actually reflects outcome of those mild-to-moderate type 2 diabetes patients with OAD only in best-equipped medical canters. However, the strength of the study is the utilization of standardized methods and central laboratory detection of biochemical parameters including HbA1c and insulin level in this cross-sectional observation, which make regional data comparable. Furthermore, intercorrelation of variables introduces collinearity into predictive statistical models, producing unreliable estimates and making it difficult to ascertain which variables represent the dominant physiological processes.36 In our study, we use method of factor analysis, which has long been used in psychometric research to deal with this problem and has been an increasing use to analyze physiological relationships. The analysis identify two independent factors which define as lipid factor and mental health factor underlying clustering of the basic risk variables of poor glycaemic control.
In conclusion, approximately one half of these outpatients with T2DM from the medical centers in big cities in China had inadequate glycaemic control with OAD alone. The gap between current situation of glycaemic control and the recommended glycaemic targets strongly supports the necessity to promote awareness of treat-to-target treatment. Our results demonstrate improvement in diabetes control during the past decade in China and raise the question of the need for more effective educational and therapeutic approaches which should be focused on enhancing physical exercise, weight control, management of dyslipidaemia, and also minimizing the risk and fear of hypoglycemia.
The authors are grateful to all the participating medical centers for authorizing us to report this work.
The following is the complete list of all the participating medical centers of this study. (1) The People's Hospital of Peking University, Beijing; (2) Tongren Hospital, affiliated to Capital Medical University, Beijing; (3) Peking University First Hospital, Beijing; (4) Xuanwu Hospital of Capital Medical University, Beijing; (5) The Chinese People's Liberation Army General Hospital, Beijing; (6) The Second Affiliated Hospital of Dalian Medical University, Dalian; (7) The First Hospital of China Medical University; Shenyang; (8) Tianjin Medical University Metabolic Diseases Hospital, Tianjin; (9) Zhongshan Hospital of Fudan University, Shanghai; (10) Changzheng Hospital of the Second Military Medical University; Shanghai; (11) Rui Jin Hospital of Shanghai Jiao Tong University, Shanghai; (12) East Hospital of Tongji University; Shanghai; (13) Changhai Hospital of the Second Military University, Shanghai; (14) Jiangshu Province Hospital, Nanjing; (15) Shenzhen Hospital of Peking University, Shenzhen; (16) Sun Yat-sen Memorial Hospital, the Second Affiliated Hospital of Sun Yat-sen University, Guangzhou.
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Keywords:© 2011 Chinese Medical Association
type 2 diabetes mellitus; glycaemic control; haemoglobin A1c; oral antidiabetic drug; obsevational study