Hypoglycemia and Fibromyalgia
Hypoglycemia (also referred to as low blood sugar, or low blood glucose) occurs when blood glucose levels drop below normal thresholds. Glucose is a vital source of energy for the body and is most abundant in dietary sources of carbohydrates. Examples of high-carbohydrate foods include bread, potatoes, rice, tortillas, cereal, milk, and fruit. After eating, glucose is absorbed into the blood where it is then transported to the body’s cells. The hormone known as insulin then helps cells use the glucose for energy production. If more glucose than needed is consumed, the excess can be stored as glycogen in the liver and muscles, or as fat stored in fat cells.
Normal blood glucose levels for non-diabetic individuals range from 70 to 99mg/dL upon waking or fasting, and between 70 and 140 mg/dL after meals. In diabetics, optimal pre-meal blood glucose levels should range from 70 to 130 mg/dL and be lower than 180 mg/dL one to two hours following the start of a meal. When blood levels of glucose start to fall, the pancreas releases a hormone known as glucagon, which signals the liver to release stored glucose back into the bloodstream. Incidents of hypoglycemia can occur suddenly and are usually quickly resolved by eating or drinking a small amount of a carbohydrate-rich food. However, if it is not treated, hypoglycemia can lead to confusion, clumsiness, shaking, dizziness, anxiety, difficulty speaking, and fainting. In severe cases, it can result in seizures, coma, or death.
Hypoglycemia is most often experienced as a side effect of diabetes treatment; however, it can occur in individuals without the disease. There are two types of hypoglycemia that can arise. The first is called reactive hypoglycemia (also known as postprandial hypoglycemia). This type of hypoglycemia occurs within four hours of eating meals. The second type is known as fasting hypoglycemia (or postabsorptive hypoglycemia), and is frequently the result of an underlying disease process. The symptoms of both types of non-diabetic hypoglycemia are similar to their diabetic counterpart, and include sweating, shakiness, dizziness, hunger, lightheadedness, sleepiness, confusion, difficulty speaking, and anxiety.
Reactive hypoglycemia occurs in approximately 30% of young women, mainly in those who are obese and under age 45. Reactive hypoglycemia is typically diagnosed by physical exam, assessing signs and symptoms, taking a blood sample while the patient is symptomatic and having it analyzed at a laboratory for glucose level, and determining if the symptoms improve after the blood glucose level returns to 70mg/dL or above. Blood glucose below 70 mg/dL at the time symptoms present – and experiencing relief from symptoms after eating – confirms a diagnosis of reactive hypoglycemia.
The causes of reactive hypoglycemia are not very well understood. Some research suggests that certain individuals may be more sensitive to the effects of the hormone epinephrine, which is responsible for many of the symptoms of hypoglycemia. Other researchers think that deficient glucagon production may be to blame. Nevertheless, a few causes of reactive hypoglycemia are known. They include gastric or stomach surgery, as well as certain rare enzyme deficiencies that are usually diagnosed early in life.
Reactive hypoglycemia can be relieved by enacting several behavioral modifications, including: 1) eating small meals or snacks approximately every three hours; 2) increasing physical activity; 3) consuming a variety of foods, including proteins (lean meat, poultry, or fish), starchy foods like whole-grain breads and potatoes, fruits and vegetables, and dairy products; 4) consuming foods that are high in fiber; and 5) limiting intake of high-sugar foods.
Fasting hypoglycemia is diagnosed by a blood glucose level below 50 mg/dL following an overnight fast, between meals, or after physical exercise. It can be caused by a number of factors, including medications, illnesses, alcohol consumption, hormonal deficiencies, and certain cancers. Medications that can lead to fasting hypoglycemia include high doses of aspirin, sulfa medications (commonly used to treat bacterial infections), pentamidine (used to treat pneumonia), and quinine (used to treat malaria). Hypoglycemia that results from excessive alcohol intake can be extremely severe and in some cases fatal, as alcohol impairs the liver’s ability to raise blood glucose levels. Illnesses that can cause fasting hypoglycemia include those that affect the liver, heart or kidneys, sepsis (overwhelming systemic infection), and starvation. For illness-related fasting hypoglycemia, treating the underlying illness will reverse the hypoglycemia. In children, hormonal deficiencies can cause fasting hypoglycemia, but they are rarely causal factors for adults. Insulin-producing pancreatic tumors can also lead to fasting hypoglycemia.
Hypoglycemia and Fibromyalgia
Little scientific research is available regarding hypoglycemia and fibromyalgia, although anecdotal reports suggest that hypoglycemia – in particular reactive hypoglycemia – is common among individuals with fibromyalgia. The fact that reactive hypoglycemia is highly prevalent among obese women who are under age 45 (a demographic profile that also describes many fibromyalgia patients), lends credibility to these anecdotal reports.
One research study has indirectly investigated various hormones in fibromyalgia patients who underwent controlled (i.e., laboratory-induced) hypoglycemia for the purposes of a research study. This 1999 study by Adler et al. compared various hormone levels between fibromyalgia patients and healthy controls following controlled decreases of blood glucose to induce hypoglycemia. The 15 fibromyalgia patients were all females who met the 1990 American College of Rheumatology criteria for the diagnosis of fibromyalgia; the 13 control subjects were healthy, premenopausal women. Following the controlled glucose decreases, the women with fibromyalgia demonstrated a significant 30% reduction in their epinephrine response to hypoglycemia. In addition, this epinephrine response was inversely associated with the fibromyalgia patients’ overall health status as measured by the Fibromyalgia Impact Questionnaire (FIQ). Based on their findings, the researchers concluded that individuals with fibromyalgia may have an impaired ability to respond to hypoglycemia via the body’s natural epinephrine pathway (Adler et al., 1999).
Despite the lack of research regarding hypoglycemia and fibromyalgia, certain subset of the literature pertaining to hypoglycemia and glucose metabolism may be of interest to fibromyalgia patients. This is largely due to the fact that several symptoms associated with hypoglycemia (regardless of type), as well as glucose metabolism, are also common among fibromyalgia patients. These include cognitive impairment (similar to the “fibro fog” experienced by fibromyalgia patients) and sleep disturbances.
A 1996 study was undertaken to measure the effects of controlled hypoglycemia on the visual accuracy, visual contrast sensitivity, ability to judge distances, cognitive functioning, and visual processing rates of non-diabetic healthy individuals. The study evaluated twenty subjects, of whom 18 were male and 2 were female. Following the controlled hypoglycemia challenges, the researchers found that general cognitive functioning, visual contrast sensitivity, and visual processing rates were significantly impaired during the times when the participants were hypoglycemic. No changes were seen with regard to visual accuracy and distance-judging ability. In their discussion, the authors of this study state that their findings are of the most relevant importance to insulin-dependent diabetic individuals, who may be at an increased risk for disrupted information processing due to visual impairments that result from hypoglycemia (McCrimmon et al., 1996). In addition, this study was conducted with a small sample size comprised primarily of healthy male participants, therefore any generalizations or extrapolations of the findings to other populations (such as females with fibromyalgia) should be done with extreme caution, and further research into this area is warranted. Nevertheless, the observation in this study that cognitive functioning is impaired during episodes of hypoglycemia may be of interest and relevance to fibromyalgia patients who struggle with blood glucose control.
Several studies have demonstrated an association between sleep quality and the ability of the body to adequately regulate blood glucose levels. Some have examined glucose levels under controlled, experimental conditions (Scheen et al., 1996), while others have used more subjective measures to assess sleep quality, including the use of validated sleep quality questionnaires, depression rating scales, and laboratory testing to determine average blood glucose levels over a period of time (van Dijk et al., 2011). Overall, a majority of studies have looked at the impact of glucose control on sleep quality in diabetic individuals. Despite the wide variations in study design, measures, and participant characteristics, a number of studies have revealed consistent associations between sleep disorders and impaired glucose metabolism (Punjabi, 2009). However, the means by which sleep quality and glucose interact with each other have yet to be determined. Nevertheless, a small body of literature supports the hypothesis that effectively treating sleep disorders (such as insomnia and obstructive sleep apnea) can result in improvements in glucose metabolism (Punjabi, 2009). Although no studies were identified that related specifically to the impact of glucose metabolism and/or hypoglycemia on sleep quality in fibromyalgia, the ongoing research into this area holds promise for fibromyalgia patients, who almost universally suffer from severely disturbed sleep.