Diabetes Mellitus Type 2: A Literature Critique
Discussion
Rationale for the topic
Diabetes is Australia’s fastest growing chronic disease (Diabetes Australia, 2012). It is the sixth leading cause of death in Australia. Up to 60% of cases of type 2 diabetes are preventable. This makes diabetes a topic of utmost public health significance. Implementation of public health measures could reduce the incidence of diabetes, which will not only result in savings for the health budget, but also increase participation and productivity in the workforce and, most importantly, lead to better health outcomes and quality of life for Australians (Diabetes Australia, 2012). This is why I chose this topic.
Prevalence and Public Health Significance of Diabetes Mellitus type 2
Diabetes Mellitus type 2 has become one of the most significant global health issues. The International Diabetes Federation reports that about 8% of the world’s population has diabetes, and another 6.4% has impaired glucose tolerance (International Diabetes Federation, 2011). 1.7 million deaths in the Western Pacific Region were attributed to diabetes in 2012.
In Australia, it is estimated that 280 people develop diabetes daily. The 2005 Australian Diabetes, Obesity and Lifestyle Study showed that 1.7 million Australians have diabetes; however, alarmingly, up to half of these cases remain undiagnosed (Diabetes Australia, 2012).
Within Australian regions, diabetes prevalence is noted to be greater among Indigenous Australian women compared to men, in the Northern Territory's Top End compared to Central Australia, among Torres Strait Islanders compared to Aboriginals, among older (≥35 years) compared to younger (<35 years) age groups, and in remote compared to urban areas (Minges et al., 2011).
Predictions for the future prevalence of diabetes also show an increasing trend. By 2030, the global diabetes prevalence is expected to reach 9.9% (International Diabetes Federation, 2011). By 2031, it is estimated that 3.3 million Australians will have type 2 diabetes (DiabetesAustralia, 2012). Obesity, which is strongly associated with diabetes, is also predicted to increase in prevalence by 0.4 - 0.8% per year in Australia: by the year 2025, one-third of 5-19 year olds and 83% of males and 75% of females above 20 years are predicted to be overweight or obese (Haby, Markwick, Peeters, Shaw, & Vos, 2012). The World Health Organization predicts that diabetes deaths will double between 2005 and 2030 (World Health Organization, 2013).
Diabetes mellitus 2 is of crucial public health significance not simply because of its high and increasing prevalence. The enormous expenses involved in the management of diabetes and its complications at the national level, could be reduced through interventions aimed at preventing diabetes and delaying its complications. The insidious nature of diabetes allows it to remain undetected and cause organ damage for years before it is recognized; for this reason its screening is important, at least in some high risk groups. Diabetes has a chronic and unremitting course, so that if not treated early, it slowly causes irreversible organ damage and early death. Many of its risk factors (discussed below) are preventable, so that public health interventions can genuinely reduce the risk of developing diabetes. The cutoff for abnormal blood glucose has been estimated from epidemiological studies, and blood glucose levels just under the cutoff are considered ‘prediabetes’ – individuals who are on the verge of diabetes, and are likely to develop it if they do not modify their risk factors (Bergman et al., 2012). Further, the myriad of morbidities and eventual complications resulting from diabetes are so serious – heart disease, stroke, infections requiring amputations, pregnancy complications – that interventions at a public health level is necessary to reduce human suffering, and promote productivity of the workforce.
Possible public health interventions include setting policies that promote healthy nutritional and agricultural policies, encourage physical activity, and make diabetes prevention affordable for all citizens at high risk. There is a need to develop more cost-effective interventions that can meet individual needs and be offered at the community and clinical levels (Bergman et al., 2012).
Some public health measures are already being taken. Government support for diabetes patients includes access to medical services through the Medicare Benefits Schedule, and provision of medicines through the Pharmaceutical Benefits Scheme. The National Diabetes Services Scheme has been created to assist diabetes patients with self-managing their condition. The Type 1 Diabetes Insulin Pump Program also provides a subsidy for young patients under 18 years of age for purchasing an insulin pump. A web-based registration portal has been developed, to monitor the quality of healthy lifestyle programs in different areas. A 3-year Diabetes Care Project pilot project has been initiated, to coordinate multidisciplinary education and care for diabetes patients (Australian Government Department of Health and Ageing, 2012).
Risk factors for Diabetes Mellitus type 2
Being overweight and/or obese increases the risk of developing Type 2 diabetes. Lack of exercise and a sedentary lifestyle, are so strongly associated with obesity that lack of exercise can be considered a diabetes risk factor. Tobacco smoking increases the risk of developing Type 2 diabetes and diabetes-associated complications (Australian Institute of Health and Welfare, 2013). High total cholesterol levels are also associated with diabetes. Intensive lifestyle interventions can produce sustained weight loss, as well as and improvements in fitness, glycemic control, and CVD risk factors in individuals with type 2 diabetes (Wing, 2010). In children, childhood obesity and lack of physical activity are leading to increasing rates of diabetes type 2 as well (World Health Organization, 2013). Diabetes is also associated with older age. Diabetes prevalence in Australia peaks in those 75 years of age and older (Diabetes Australia, 2008). However, in the Indigenous populations, peak prevalence is in the 35–55 year old age-group, indicating a strong genetic component here (Minges et al., 2011).
A positive family history increases the risk of diabetes; indeed, variations in genes (regulating fasting blood glucose and insulin levels) have been found to be associated with diabetes mellitus 2. the diabetes type 2 phenotype is highly concordant among monozygous twins, less so among dizygous (DZ) twins. Overall, evidence indicates there is significant heterogeneity within the diabetes phenotype, with no particular gene mutations associated (Hamman, 2009). Around 20 single nucleotide polymorphisms associated with type 2 diabetes have been identified (Talmud et al., 2010). Some of these genes include ADCY5, PROX1, GCK, GCKR and DGKB-TMEM195 (Dupuis et al., 2010). Mutations in the glucokinase gene, insulin and insulin receptor genes, the adenosine deaminase gene, the glucose transporter system (especially GLUT 2 and GLUT 4), islet amyloid polypeptide (amylin), and older protein markers such as haptoglobin, Gc, and others are also implicated (Hamman, 2009).
Pancreatitis, if severe and damaging most of the pancreas, can also result in the development of diabetes type 2 (Diabetes Australia, 2008). The strongest risk factors for pancreatitis include gallstones and alcoholism, therefore, alcoholism is also indirectly linked to diabetes type 2 (Diabetes Australia, 2008).
Abnormal sleeping times, both too short ( < 6 hours) and too long ( > 9 hours), are associated with a higher risk of developing type 2 diabetes (Chaput, Després, Bouchard, Astrup, & Tremblay, 2009).
Hypertension is also a risk factor for diabetes mellitus (Raphael et al., 2010). It greatly increases the risk of complications in diabetes patients, such as cardiovascular disease, kidney disease and diabetic eye disease. Prolonged diabetes duration and poor glycemic control in diabetics also greatly increases the risk of these complications (Yau et al., 2012).
Diets low in whole grains and other sources of fiber are associated with diabetes (Whiting, Unwin, & Roglic, 2010). A high fiber diet, with increased consumption of fruits and vegetables, is recommended to reduce the risk of developing Type 2 diabetes (Australian Institute of Health and Welfare, 2013).
Gestational diabetes is diabetes mellitus during pregnancy. Abnormal glucose control can have adverse effects on the baby, which creates concerns for this condition. Risk factors for developing gestational diabetes includes obesity, body mass index > 30 kg/m2, having had a previous baby weighing more than 4 kg, particular ethnic groups (Hispanic, African, or native American), having a first degree relative with diabetes, having metabolic syndrome, and higher maternal age (Bottalico, 2007). Gestational diabetes is also a risk factor for developing chronic diabetes mellitus 2 (Diabete sAustralia, 2008).
In Australia, the ethnic groups at higher risk are Aboriginals and Torres Strait Islanders (Diabetes Australia, 2008).
Impaired fasting glycaemia (IFG) is an intermediate condition in the transition between normal glycemic control and diabetes. People with IFG are at increased risk of progressing to diabetes mellitus type 2, although it is not inevitable and can be controlled through interventions to reduce weight, and increase physical activity (World Health Organization, 2013).
Environmental and Social Determinants of Diabetes Mellitus type 2
As the prevalence of diabetes is rising alarmingly, there is an urgent need to identify and characterize its determinants beyond the basic risk factors outlined above.
The case for environmental determinants for diabetes emerged from the observation that a rapid increase in the prevalence and incidence of diabetes type 2 was occurring in populations undergoing rapid westernization, such as the South Pacific and American Indians (Hamman, 2009). This ‘westernization’ consisted of decreases in physical activity; alterations in dietary intake toward more calories, fat, and less complex carbohydrates; and urbanization. It was noted that diabetes would decrease abruptly in a population during times of decreased caloric intake. A higher intake of dietary fiber is also associated with lower fasting insulin levels, while high-fat diets have been associated with obesity and with undiagnosed diabetes. There is also some evidence of dietary alcohol contributing to diabetes. A consistent relationship is demonstrated between higher physical activity and lower incidence of insulin resistance and diabetes type 2. Thus, diet and physical activity are seen as the major environmental determinants for diabetes type 2 (Hamman, 2009). Obesity is a known risk factor – as an environmental determinant, the duration of obesity and distribution of it, are environmental determinants. It is excess abdominal obesity, correlating with visceral fat, which is associated with diabetes type 2.
Among social determinants, socio-economic position has been studied in terms of educational level, type of occupation and amount of income. Diabetes was initially considered a ‘disease of affluence’: it was thought that high-income households would have more diabetes due to greater access to food. This concept is now under controversy. In low- and middle-income countries, the prevalence of diabetes tends to be higher in urban than in rural areas, and a higher prevalence of diabetes in groups of high socioeconomic status (Whiting et al., 2010). But, in most high-income countries, the prevalence and incidence is inversely related to socioeconomic position. A recent systematic review has even shown that low socio-economic position, in high- as well as in low-income countries, is associated with the development of diabetes type 2. The greatest evidence for these determinants comes from high-income countries, while further studies are needed in low-income countries.
It is postulated that low socio-economic position leads to type 2 diabetes due to lack of access to health-care services and information, lack of availability of healthy foods and places to exercise, lack of economic and occupational opportunities, as well as individual lifestyle choices. Greater levels of long-term stress also affect the entire neuroendocrine system, causing endocrine disturbances that may lead to type 2 diabetes. Higher stress in low socio-economic positions thus may contribute to the association with diabetes (Agardh, Allebeck, Hallqvist, Moradi, & Sidorchuk, 2011). Among socio-economic determinants, education level is the most consistently associated with increased risk of disease. In Canada, research showed that individuals living more often in poverty over a 12 year period, had a 41% greater chance of developing type 2 diabetes compared to those not living in poverty (Raphael et al., 2010).
Adverse early childhood experiences, such as malnutrition and poverty have been found to be important predictors of the onset of type 2 diabetes in later life (Raphael et al., 2010).
Conclusions
Diabetes mellitus type 2 is a growing global epidemic, affecting about 8% of the world’s population and the 6th leading cause of death in Australia. Diabetes is a heterogenous condition, with genetic, environmental and social determinants. Its major risk factors are obesity and lack of physical activity; abnormal cholesterol levels, low-fiber diet, hypertension, impaired glucose tolerance, and smoking are also associated with it. Its social determinants include low socio-economic position (low education and low monthly income) and social stresses. Up to 60% of diabetes cases are preventable through the modification of determinants such as physical activity and diet. Public health programs are therefore needed to address at-risk populations for diabetes to reduce new cases, as well as to maximize treatment for diabetes so that its long-term complications can be prevented.
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