as myocardial infarctions, are the most well-recognized and feared complication of diabetes. They are caused by atherosclerosis of the blood vessels supplying the heart. The sudden blockage of these arteries starves the heart of oxygen, resulting in the death of part of the heart muscle.
The Framingham studies of the 1970s established a strong association between heart disease and diabetes.11 Diabetes increases the risk of cardiovascular disease two- to fourfold, and these complications develop at a younger age compared to nondiabetics. Sixty-eight percent of diabetics aged sixty-five or older will die of heart disease, and a further 16 percent will die of stroke.12 Reducing the risk of macrovascular disease is therefore of primary importance. The extent of death and disability resulting from cardiovascular diseases is many times greater than that resulting from microvascular diseases.
Over the past three decades, there have been significant improvements in the treatment of heart disease, but gains for diabetic patients have lagged far behind. While the overall death rate for nondiabetic men has decreased by 36.4 percent, it has only decreased 13.1 percent for diabetic men.13
Stroke
A STROKE IS caused by atherosclerosis of the large blood vessels supplying the brain. A sudden disruption of the normal blood flow starves the brain of oxygen and a portion of the brain may die. Symptoms vary depending upon which part of the brain is affected, but the devastating impact of stroke cannot be underestimated. In the United States, it is the third leading cause of death and the biggest contributor to disability.
Diabetes is a strong independent risk factor in stroke, meaning that, on its own, diabetes increases a person’s risk of having a stroke by as much as 150–400 percent.14 Approximately a quarter of all new strokes occur in diabetic patients.15 Every year of diabetes increases the risk of stroke by 3 percent,16 and the prognosis is also far worse.
Peripheral vascular disease
PERIPHERAL VASCULAR DISEASE (PVD) is caused by atherosclerosis of the large blood vessels supplying the legs. The disruption of normal blood flow starves the legs of oxygen-carrying hemoglobin. The most common symptom of PVD is pain or cramping that appears with walking and is relieved by rest. As the blood vessels narrow and circulation worsens, pain may also appear at rest and especially at night. PVD significantly reduces mobility, which can lead to long-term disability.
Skin with a poor blood supply is more likely to be damaged and takes longer to heal. In diabetics, minor cuts or injuries to the feet may become non-healing foot ulcers. In severe cases, these areas where the skin has broken down, revealing underlying tissue, can progress to gangrene. At this point, blood supply has been greatly reduced or completely lost, the tissue dies, and amputation of the affected limb—a treatment of last resort—often becomes necessary to treat chronic infections and relieve pain.
Diabetes, along with smoking, is the strongest risk factor for PVD. Approximately 27 percent of diabetic patients with PVD will progressively worsen over a five-year period, and 4 percent of them will need an amputation.17 Patients with gangrene and those requiring amputation may never walk again, which can result in a cycle of disability. A loss of function of the limbs leads to less physical activity, which in turn leads to progressive deconditioning of the muscles. Weaker muscles lead to less physical activity, and the cycle repeats.
OTHER COMPLICATIONS
Alzheimer’s disease
ALZHEIMER’S DISEASE IS a chronic, progressive, neurodegenerative disease that causes memory loss, personality changes, and cognitive problems. It is the most common form of dementia, and the sixth leading cause of death in the United States.18 Alzheimer’s disease may reflect the inability to use glucose normally, perhaps a type of selective insulin resistance in the brain. The links between Alzheimer’s disease and diabetes have grown so strong that many researchers have suggested Alzheimer’s disease can be called type 3 diabetes.19 These arguments go far beyond the scope of this book, however.
Cancer
TYPE 2 DIABETES increases the risk of most common cancers, including breast, stomach, colorectal, kidney, and endometrial cancers. This may be related to some of the medications used to treat diabetes and will be further discussed in chapter 10. The survival rate of cancer patients with pre-existing diabetes is far worse than for nondiabetics.20
Fatty liver disease
NON-ALCOHOLIC FATTY liver disease (NAFLD) is defined as the storage and accumulation of excess fat in the form of triglycerides exceeding 5 percent of the total weight of the liver. This condition can be detected using an ultrasound to examine the abdomen. When this excess fat causes damage to the liver tissue, which can be revealed through standard blood tests, it is called non-alcoholic steatohepatitis (NASH). Current estimates suggest that NAFLD affects 30 percent and NASH 5 percent of the U.S. population; both are important causes of liver cirrhosis (irreversible scarring of the liver).21
NAFLD is virtually non-existent in recent-onset type 1 diabetes. By contrast, the incidence in type 2 diabetes is estimated at upwards of 75 percent. The central role of fatty liver is more fully explained in chapter 7.
Infections
DIABETICS ARE MORE prone to all types of infections, which are caused by foreign organisms invading and multiplying in the body. Not only are they more susceptible to many types of bacterial and fungal infections than nondiabetics, the effects also tend to be more serious. For example, diabetics have a four- to fivefold higher risk of developing a serious kidney infection.22 All types of fungal infections, including thrush, vaginal yeast infections, fungal infections of the nails, and athlete’s foot, are more common in diabetic patients.
Among the most serious infections for diabetics are those involving the feet. Despite adequate blood glucose control, 15 percent of all diabetic patients will develop non-healing foot wounds during their lifetime. Infections in these wounds often involve multiple microorganisms, making broad-spectrum antibiotic treatment necessary. However, the decreased blood circulation associated with PVD (see above) contributes to the poor wound healing. As a result, diabetics have a fifteen-fold increased risk of lower-limb amputation, and account for over 50 percent of the amputations done in the United States, excluding accidents. It is estimated that each of these cases of infected diabetic foot ulcers costs upwards of $25,000 to treat.23
There are many contributing factors to the higher rates of infection. High blood glucose may impair the immune system. As well, poor blood circulation decreases the ability of infection-fighting white blood cells to reach all parts of the body.
Skin and nail conditions
NUMEROUS SKIN AND nail conditions are linked to diabetes. Generally, they are more of an aesthetic concern than a medical one; however, they often indicate the underlying serious condition of diabetes, which requires medical management.
Acanthosis nigricans is a gray-black, velvety thickening of the skin, particularly around the neck and in body folds, caused by high insulin levels. Diabetic dermopathy, also called shin spots, are often found on the lower extremities as dark, finely scaled lesions. Skin tags are soft protrusions of skin often found on the eyelids, neck, and armpits. Over 25 percent of patients with skin tags have diabetes.24
Nail problems are also common in diabetic patients, particularly fungal infections. The nails may become yellowy-brown, thicken, and separate from the nail bed (onycholysis).
