Diabetes



Diabetes



Barbara J. Ehrmann


Introduction


Diabetes mellitus is a prevalent disease, especially among the elderly. In the last 15 years alone, the prevalence of diagnosed diabetes cases has increased by 82%, mostly because of the increase in obesity. Age-related changes involving decreased insulin sensitivity in the peripheral tissues and reduced insulin control of hepatic glucose output, coupled with physical inactivity and increased obesity, contribute to higher incidences of abnormal glucose tolerance in the older population.


It is estimated that the prevalence of diabetes for all age groups worldwide was 8.3% in 2011 and will be 9.9% in 2030. The International Diabetes Federation (2013) reports the total number of people with diabetes in 2013 to be 382 million and has estimated that this number will rise to 582 million in 2035. The increasing proportion of individuals who are older than 65 years of age is an important demographic influence.


Diabetes is more prevalent in certain populations, for example Native American/Native Alaskans, Hispanic/Latino Americans and African Americans. Approximately 25.8 million people in the United States of America, or 8.3% of the total US population, have diabetes mellitus. Of those aged 65 or above, 10.9 million, or 26.9%, have diabetes. It is estimated that one-third of these individuals are unaware of their disease. Further, it is estimated that 79 million adults have impaired glucose tolerance (IGT), or prediabetes, a condition that often precedes diabetes mellitus. Diabetes mellitus is a serious disease that causes a wide range of complications. In 2007 the total cost of diabetes in the US was $174 billion, $40 billion of which resulted from indirect costs because of disability, work loss or premature mortality (National Diabetes Fact Sheet, 2011).


Classification and diagnosis of diabetes mellitus


Diabetes mellitus is characterized by hyperglycemia. There are four clinical classes of diabetes including type 1, type 2, other specific types of diabetes (genetic defects in ß-cell function or insulin action, disease of exocrine pancreas, drug- or chemically induced diabetes) and gestational diabetes mellitus (GDM). For the purposes of this chapter, discussion will focus on type 1 and type 2 diabetes (see Table 46.1).



In 2009, the American Diabetes Association (ADA) modified the diagnostic criteria for the classification of impaired fasting glucose (IFG) to include both fasting glucose and hemoglobin a1c (a1c) levels. a1c or glycosylated hemoglobin is a measure of blood sugar control which measures a person’s average glucose level over the previous 2–3 months. This shows the amount of glucose that is attached to the red blood cells, which is proportional to the amount of glucose in the blood.


There are three ways to diagnose diabetes, each of which must be confirmed on a subsequent day unless there are definitive symptoms of hyperglycemia, such as excess thirst and urination (polydipsia and polyuria), and unexplained weight loss accompanied by increased or normal food intake. The criteria for the diagnosis of diabetes include the following: (i) fasting plasma glucose (FPG) of greater than 126 mg/dl (fasting is defined as no caloric intake for at least 8 hours); (ii) 200 mg/dl or higher on an oral glucose tolerance test (OGTT) with 75 g of glucose; (iii) a1c of 6.5% higher (used for diagnosis of type 2 diabetes only). FPG is the preferred test for diagnosing diabetes in nonpregnant adults. Other common presenting symptoms of diabetes include poor wound healing, fatigue, vaginal yeast infections and blurred vision (American Diabetes Association, 2013a).



Hyperglycemia that is not sufficient to meet the diagnostic criteria for diabetes is categorized as IFG, IGT or prediabetes. IFG is defined as a FPG between 100 mg/dl and 125 mg/dl. IGT is defined as an OGTT between 140 mg/dl and 199 mg/dl. Prediabetes, type 2, is also diagnosed with an a1c between 5.7 and 6.4% (American Diabetes Association, 2013a).


Types of diabetes mellitus


Type 1


Type 1 diabetes is caused by autoimmune destruction of the insulin-producing ß-cells of the pancreatic islets, resulting in insulin deficiency. As a result, these patients have an absolute need for insulin therapy. The age of onset of type 1 diabetes is most commonly during childhood or young adulthood, although it can begin at any age. In the absence of insulin replacement, patients with type 1 diabetes develop severe hyperglycemia and metabolic acidosis, which results from the excess production of ketones, by-products of fat breakdown in the absence of insulin. Diabetic ketoacidosis (DKA) is a medical emergency.


Type 2


Of all individuals with diabetes, 90–95% have type 2 diabetes. This has historically been a disease of adults, with its incidence increasing with each decade of aging. However, type 2 diabetes is increasingly being diagnosed in children and adolescents. Type 2 diabetes is associated with obesity, a family history of diabetes, a previous history of gestational diabetes, IGT and physical inactivity. Other factors associated with type 2 diabetes are race/ethnicity, with African Americans, Hispanic/Latino Americans, Native Americans and some Asian Americans and other Pacific Islanders being at particularly high risk. Type 2 diabetes is regarded as being a metabolic disorder that is linked to a modern lifestyle involving stress, excess caloric intake (particularly fat) and inadequate physical activity. From a metabolic perspective, these patients generally have the twin defects of sluggish secretion of insulin following meals (leading to poor overall insulin production with long duration) and peripheral insulin resistance (reduced cellular uptake and utilization of insulin).


Metabolic syndrome


An elevated fasting glucose is one of several risk factors that is known to increase an individual’s risk of developing heart disease, stroke and diabetes. These risk factors, grouped together, are called the ‘metabolic syndrome’. Other characteristics include obesity, particularly abdominal fat, hyperlipidemia and hypertension. The criteria for metabolic syndrome are met by having any three of the following risk factors, as recently defined by the American Heart Association and International Diabetes Federation: (i) an elevated waist circumference (abdominal obesity); (ii) an elevated triglyceride level of 150 mg/dl or greater; (iii) a reduced high-density lipoprotein (HDL – ‘good cholesterol’) level of less than 40 mg/dl for men and less than 50 mg/dl for women; (iv) an elevated blood pressure of 130/85 mmHg or higher; and (v) an elevated fasting glucose of 100 mg/dl or higher (Alberti et al., 2009). Fifty-two percent of males and 54% of females in the US over the age of 60 met the criteria for metabolic syndrome for the years 2003–2006 (Ervin, 2009).


Therapeutic intervention


Newly diagnosed diabetes


Patients newly diagnosed with diabetes mellitus have a special need for comprehensive education. Diabetes self-management education is an integral component of medical care. The onset of diabetes can be precipitated by physical and emotional stress and other illnesses and, usually, the diabetic state persists. In addition, certain medications, most notably oral or parenteral steroid therapy, can trigger the onset of diabetes mellitus or upset metabolic control in a previously diagnosed patient.



Medical treatment


Diet and exercise are the cornerstones of the treatment of type 2 diabetes mellitus and many individuals with diabetes can control their blood glucose by following a careful diet and exercise program, losing excess weight and taking oral hypoglycemic agents (medications that lower plasma glucose levels). A meta-analysis of 27 studies found reductions in a1c with aerobic and/or resistance training (Snowling & Hopkins, 2006). Generally, it is not necessary to increase food intake before exercise of short duration or low intensity. Exercise of moderate intensity may be preceded by consuming 10–15 g of carbohydrate, although this is often unnecessary.


Among adults with diagnosed diabetes, about 14% take both insulin and oral medications, 12% take insulin only, 58% take oral medications only and 16% take neither insulin nor oral medications (American Diabetes Association, 2013b).


Glycemic control in patients with type 1 and 2 diabetes is most often measured using levels of blood glycosylated hemoglobin, or hemoglobin A1c (A1c), in addition to self-monitoring of blood glucose. The A1c level reflects the mean blood glucose concentration over the previous 6–12 weeks. The ADA’s current glycemic goal for nonpregnant adults is a value of less than 7.0% (compared with a normal nondiabetic range of 4–6%).


The ADA recommends that blood pressure in patients with diabetes should be less than 140/80 mmHg. Lipid goals for patients with diabetes include a low-density lipoprotein (LDL) level of less than 100 mg/dl, triglyceride level less than 150 mg/dl and HDL level greater than 50 mg/dl (<1.1 mmol/l) (American Diabetes Association, 2013b).


Insulin therapy for type 1 diabetes


Therapy for individuals with type 1 diabetes always includes insulin. Insulin is given by subcutaneous injection or with an insulin pump, which also delivers insulin subcutaneously. Combinations of rapid-, short-, intermediate- or long-acting insulin are used, such as Humalog, Regular, NPH and glargine respectively. In most centers, patients with type 1 diabetes are treated with two or three doses per day of rapid- or short-acting insulin combined with intermediate-acting insulin. Cross-sectional studies have not documented improved control with an increasing number of insulin injections per day, showing that the number of injections alone is not sufficient to achieve optimal glycemic control. The method of using long-acting insulin (glargine) combined with rapid-acting insulin (Humalog), given before meals and snacks, provides greater flexibility but requires a knowledge of carbohydrate counting and the use of an insulin–carbohydrate ratio. Because blood glucose can fluctuate widely in patients with type 1 diabetes, it is recommended that blood glucose be monitored several times a day, before meals and at bedtime, and insulin doses adjusted accordingly.


Treatment of type 2 diabetes


Oral treatment options for patients with type 2 diabetes are diverse. Control can be achieved with diet and exercise therapy, especially if weight loss is achieved in an overweight patient. However, most type 2 patients also require some pharmacological treatment, either oral hypoglycemic medication or insulin. Oral medications include the sulfonylureas (e.g. glyburide, glipizide, chlorpropamide) and meglitinides, which increase insulin release; thiazolidinediones (rosiglitazone, pioglitazone) and biguanides (metformin), which increase target tissue sensitivity to insulin and reduce glucose production in the liver; acarbose, which slows down the absorption of carbohydrate through the intestine; and prandial glucose regulators (repaglinide), which are taken with meals and help to increase insulin release. These medications can be used alone or in combination.


Another injectable drug can be used to treat type 2 diabetes. Exenatide is a new class of drug known as an incretin memetic. Incretins, such as glucagon-like peptide (GLP-1), are produced in the small intestine and released in response to meals. GLP-1 stimulates insulin secretion and suppresses glucagon release. Exenatide is used in type 2 diabetics to increase insulin secretion when oral medications are not enough.


The United Kingdom Prospective Diabetes Study (UKPDS) showed that good glycemic control in patients with type 2 diabetes results in a reduction in the risk of microvascular disease (UKPDS, 1998). Specifically, a 1% fall in a1c was associated with a 35% reduction in microvascular complications (retinopathy, nephropathy and neuropathy). Based on the results of the UKPDS, normoglycemia is now the goal for most patients with type 2 diabetes. Although insulin may be considered for initial therapy in type 2 diabetes, especially if the patient presents with a very elevated a1c level, it is most often used when hyperglycemia persists despite the use of oral hypoglycemic agents.


Hypoglycemia


The main adverse effect of insulin or oral therapy is hypoglycemia (low blood glucose). In a patient with diabetes, symptoms of hypoglycemia generally have a rapid onset and occur when blood glucose is less than 70–80 mg/dl (Table 46.2). A severe reaction can occur below 60 mg/dl. A patient may complain of shakiness and sweating or other symptoms caused by increased epinephrine (adrenaline) release, such as tachycardia and anxiety. Deprivation of glucose in the central nervous system causes blurred vision, weakness, confusion, slurred speech and, potentially, seizure and coma, with permanent neurological damage. Symptoms of hypoglycemia may be blunted in a patient with long-standing diabetes, especially the early warning signs of nervousness, tremor and sweating. The initial symptom in patients with long-standing diabetes mellitus may be confusion.

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Jun 22, 2016 | Posted by in PHYSICAL MEDICINE & REHABILITATION | Comments Off on Diabetes

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