Diabetes mellitus type 1 is an autoimmune disease that destroys the beta cells of the pancreas, leading to insulin deficiency. The resulting hyperglycemia can lead to microvascular and macrovascular disease. The microvascular complications include retinopathy, nephropathy, and neuropathy. The macrovascular complications include coronary artery disease, peripheral vascular disease with amputation, stroke, and renal disease. The disease usually manifests early in life, although it can also occur in adulthood.
Diabetes mellitus type 2 is a familial hyperglycemia that occurs primarily in adults but can also occur in children and adolescents. It is caused by an insulin resistance whose etiology is multiple and not totally understood. The net result of the insulin resistance is to initially cause a compensatory hyperinsulinemia. Subsequently, the beta cells of the pancreas fail to meet the compensatory need, less insulin secretion occurs than is required for the adequate elimination and utilization of glucose, and hyperglycemia results. Dyslipidemia and hypertension are common in patients with type 2 diabetes, and about 80 percent of patients with type 2 diabetes are obese (LaPorte et al., 1995). The complications arising from this condition are the same as those described for type 1 diabetes mellitus. Because of the later age of onset in persons with type 2 compared to type 1 diabetes, evidence of clinically significant microvascular complications is less.
Estimates of prevalence have increased over the years in part due to more stringent diagnostic criteria as well as the continued rise in obesity.
In 1997, the diagnostic criterion for a diagnosis of diabetes was lowered from a fasting glucose tolerance test result of 140 mg/dL to 126 mg/dL (American Diabetes Association, 1997). Based on the diagnostic criteria of a fasting glucose tolerance test of 110 to 126 mg/dL as impaired glucose tolerance and greater than or equal to 126 mg/dL as diabetes, 18.4 percent or 6.3 million people age 65 or older have diabetes. Approximately 40 to 45 percent of persons age 65 years or older have either type 2 diabetes or impaired glucose tolerance. Diabetes is the seventh leading cause of death in the United States, and more than 187,000 persons died from the disease and its complications in 1995 (HCFA, 1999).
Individuals with diabetes mellitus, regardless of type, typically have several risk factors associated with increased morbidity and mortality. The risk factors include abnormal fasting glucose, postprandial glucose, hemoglobin A1c (HbA1c), low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, triglycerides, microalbuminuria, blood pressure, a procoagulant state, and abdominal obesity.
EVIDENCE THAT A CHANGE IN RISK FACTORS CHANGES MORBIDITY AND MORTALITY
A series of long-term, randomized, controlled trials shows the effect of tight glucose and HbA1c control on complications of the disease and are described below.
Diabetes Control and Complications Trial
Investigators in the Diabetes Control and Complications Trial (DCCT), a randomized controlled trial, followed 1,400 patients with type 1 diabetes, between the ages of 15 and 39 years, for 7 years to determine what effect normalizing blood glucose and HbA1c had on chronic complications of the disease (DCCT Research Group, 1993). The study showed a sustained difference in the levels of glucose and HbA1c between the conventionally treated group and the tightly controlled experimental group. The trial was stopped after 7 years because of the significant lowering of microvascular complication rates in the experimental group compared to the conventionally treated control group. Microvascular disease was defined as retinopathy, neuropathy, and urinary albumin excretion. All three end points showed a significant difference. Macrovascular disease events in diabetes usually include myocardial infarction, sudden death, stroke, and peripheral vascular disease. While the DCCT study lacked the statistical power to detect a difference in macrovascular disease in this relatively young population with type 1 diabetes, a trend toward a lower
incidence of macrovascular end points was suggested in the tightly controlled group.
Stockholm Diabetes Intervention Study
This small randomized clinical trial of 102 patients with type 1 diabetes included a group that was treated intensively and a group with usual care (Reichard et al., 1993). The patients’ age at baseline was 30 ± 8 years in the intensive group and 32 ± 7 years in the standard group. The intensive group had extensive educational intervention, including blood glucose monitoring, and most of the patients (82 percent) took at least three insulin injections daily. The standard treatment group continued with routine diabetes care. The patients were followed for 7.5 years. As in the DCCT, intensive glucose control led to a decreased incidence of microvascular complications (retinopathy, nephropathy, and neuropathy). Macrovascular end points were not assessed.
This randomized controlled trial in Japan (Ohkubo et al., 1995) studied the effect of multiple insulin injections versus conventional insulin injections in 110 middle-aged patients with type 2 diabetes. The appearance and progression of retinopathy, nephropathy, and neuropathy were evaluated every 6 months over a 6-year period. The group with the tight control had significantly lower HbA1c values and developed fewer microvascular complications. Although the study lacked the statistical power to measure the effect on macrovascular disease, the trend was for fewer events in the tightly controlled group.
Veterans Affairs Diabetes Feasibility Trial
Investigators in this pilot study randomized 153 men with type 2 diabetes to either conventional or intensive insulin therapy (Abraira et al., 1997). The mean age was 60 ± 6 years and the length of diagnosis of non-insulin-dependent diabetes mellitus was 7.8 ± 4.0 years. While the standard treatment was one injection each morning, intensive insulin therapy was a stepped plan with up to multiple insulin injections as necessary to attain near normal glycemia. Despite a 2 percent absolute HbA1c difference in glycemic control between the two groups, which were followed for an average of 27 months, the trial reported no significant difference in cardiovascular events (when adjusted for baseline characteristics). Cardiovascular events were defined as myocardial infarction, stroke, and
sudden death. This pilot study did not have the statistical power to come to a definite conclusion concerning macrovascular end points.
United Kingdom Prospective Diabetes Study
The United Kingdom Prospective Diabetes Study (UKPDS) was a large, multicenter randomized control trial in which 3,867 patients with type 2 diabetes were followed for 10 years (UKPDS Group, 1998). The median age of patients was 54 years at baseline, with a range of 48 to 60 years. The study compared the effects of intensive blood glucose control with either sulfonylureas, insulin, or conventional treatment on both microvascular and macrovascular complications. Treatment for all groups included a standard diet, exercise prescription, and/or drugs as needed to attain the designated level of blood glucose control for each group. The aim in the intensive group was a fasting plasma glucose (FPG) of less than 108 mg/dL. The aim in the conventional group was the best achievable FPG with diet or exercise alone. Drugs were added in the conventional group only if there were hyperglycemic symptoms or FPG of at least 270 mg/dL. To assess differences between conventional and intensive treatment the study focused on three aggregate end points:
any diabetes-related end point (sudden death, death from hyperglycemia or hypoglycemia, fatal or nonfatal myocardial infarction, angina, heart failure, stroke, renal failure, amputation, vitreous hemorrhage, retinopathy requiring photocoagulation, blindness in one eye, or cataract extraction);
diabetes-related death (defined as death from myocardial infarction, stroke, peripheral vascular disease, renal disease, hyperglycemia or hypoglycemia, and/or sudden death); and
All analyses included the intention-to-treat model, where all patients assigned to a particular protocol are followed to the end as part of that group, whether they carry out the intervention or not. Over 10 years, HbA1c was 7.0 percent in the intensive group and 7.9 percent in the conventional group. Compared to the conventional group, the risk in the intensive group was 12 percent lower for any diabetes-related end point, 10 percent lower for any diabetes-related death, and 6 percent lower for all-cause mortality. There was a 25 percent reduction in microvascular end points in the intensive compared to the conventional group (p = 0.0099). Tighter control significantly reduced the development of retinopathy and nephropathy, and was borderline with regard to neuropathy. Epidemiological analysis of the UKPDS data showed a continuous rela-
tionship between the risk of microvascular complications and glycemia. For every percentage point decrement in HbA1c (e.g., 9 to 8 percent), a 35 percent reduction in the risk of microvascular complications occurred. The effect of tighter control on macrovascular disease resulted in a nonsignificant trend, with a 16 percent reduction in the risk of combined fatal or nonfatal myocardial infarction and sudden death in the intensively treated group. Tight control of blood pressure (<134/82 mm Hg) had a profound effect on both micro- and macrovascular complications in both the intensive and the conventional treatment groups, significantly reducing strokes, diabetes-related deaths, heart failure, microvascular complications, and visual loss. This landmark study confirms that for inpatients with type 2 diabetes, lowering blood glucose is definitely beneficial in reducing macrovascular complications and reemphasizes the importance of blood pressure control in patients with diabetes mellitus.
THE ROLE OF NUTRITION INTERVENTION IN THE MANAGEMENT OF DIABETES
Nutrition intervention is considered an essential component in the management of diabetes. For this reason, it has been provided to participants in both control and intervention groups of studies designed to evaluate the impact of improved glycemic control on the development of diabetic complications in both patients with type 1 and 2 diabetes (DCCT Research Group, 1993; UKPDS Group, 1998). While there are few studies in which nutrition intervention is the only variable (Bitzen et al., 1988; Franz et al., 1995; Kulkarni et al., 1998), many studies have demonstrated the effectiveness of multidisciplinary patient education which includes a nutrition component on glycemic control (Agurs-Collins et al., 1997; García and Suárez, 1996; Gilden et al., 1989; Glasgow et al., 1992).
While these studies demonstrate improved outcomes, it is difficult to tease out benefits specifically attributable to the nutritional component of the education. Researchers have studied diabetes patient education extensively. Three meta-analyses have shown that patient education is effective in improving knowledge, skills, psychosocial adjustment, and metabolic control (Brown, 1988, 1990; Padgett et al., 1988). Overall, evidence from many types of studies involving nutrition therapy in the management of diabetes is supportive of nutrition intervention. The American Diabetes Association has recognized the value of medical nutrition therapy and considers it an essential component of diabetes management (American Diabetes Association, 1999b).
Nutrition Intervention in Trials of Intensive Management
In the DCCT study, the control and intervention groups both received counseling by a dietitian. However, while the control group received nutrition counseling every 6 months, the intensive management group received nutrition counseling every month. In the DCCT, several behaviors were shown to be associated with lower HbA1c levels among patients with type 1 diabetes randomized to intensive insulin therapy (Delahanty and Halford, 1993). Within the intensively managed group, those who reported following their prescribed diets had average HbA1c levels 0.9 percent lower than those who did not follow their meal plan. Adjusting food and/or insulin resulted in significantly lower HbA1c levels. This substudy on 687 patients provides evidence that dietary behaviors positively alters indicators of glycemic control when used in combination with appropriate insulin management (Delahanty and Halford, 1993).
In the UKPDS study, all treatment and control groups received nutritional advice from a dietitian every 3 months. Initial monthly clinic visits resulted in an average weight loss of 5 kg after 3 months (UKPDS Group, 1995).
Nutrition Intervention as a Component of Diabetes Education
García and Suárez (1996) described a continuing interactive educational model for elderly patients with diabetes. Elderly individuals who had previously attended the Diabetes Basic Information Course at the National Institute of Endocrinology in Havana, Cuba were invited to participate in small interactive groups (≤15 participants) with no more than two health professionals over a period of 5 years. The health professionals included an endocrinologist, health educator, teaching nurse, dietitian, podiatrist, and social worker. A total of 148 elderly individuals (mean age 72 years) along with many spouses attended the monthly sessions. Data showed a significant increase in diabetes self management knowledge and skills (p < 0.001), a reduction in body weight (p < 0.01), and a reduction in the need for medication (p < 0.05). Overall, mean levels of HbA1c declined from 12.4 percent to 7.9 percent after 5 years (p < 0.02). The need for emergency services declined from 97 percent in the year before the course to less than 2 percent after 5 years (p = 0.000). In addition, the social support and education received through this interactive model overall resulted in patients feeling “less sick, depressed and isolated” (García and Suárez, 1996).
Gilden and colleagues (1989) demonstrated improvement in quality of life outcomes for older patients and their spouses. They evaluated the
outcomes of 45 older male patients who ranged in age from 65 to 82 years (mean age 70 years) following 6 weeks of diabetes education (one session per week). A multidisciplinary team including a diabetologist, nurse-educator, dietitian, psychologist, podiatrist, and social worker administered the program. Results indicated a reduction in stress that correlated with their increase in knowledge (p < 0.05) and their improved diet-related quality of life (p < 0.02). The decrease in stress level was still apparent 6 months later (p < 0.01). Their perceived quality of life with regard to lifestyle modifications such as diet and exercise increased (p < 0.01) and was still evident after 6 months (Gilden et al., 1989).
The Diabetes Care for Older Adults Project was a 3-year randomized clinical trial that compared an intensive team care program to conventional therapy in 103 participants with a mean age of 70 years. Diabetes education and social support were provided by an interdisciplinary team consisting of a clinical nurse specialist, a dietitian, both of whom were certified diabetes educators (CDE), and a social worker. Glycosylated hemoglobin dropped an average of 3.2 percentage points in the treatment group versus 1.0 percentage point in the control group after an 18-month intervention period in which groups met 12 times (Funnell et al., 1997; Halter et al., 1993).
Glasgow and colleagues (1992) studied 102 patients over the age of 60 with type 2 diabetes in a crossover intervention using a multidisciplinary team that included a registered dietitian. Results demonstrated a significantly greater reduction in caloric intake and percent of calories from fat in the intervention group compared to the control group who received delayed intervention. In this crossover study, the intervention resulted in a decline in HbA1c from 6.8 percent to 6.3 percent. The HbA1c rebounded to 6.7 percent during the subsequent control period. When control patients crossed over to the intervention, their HbAlc declined from 7.4 percent to 6.4 percent (Glasgow et al., 1992).
In a randomized control trial, researchers randomly assigned 64 overweight African-American patients (55–79 years) with type 2 diabetes to one of two groups. Subjects participated in either one individual and eighteen group sessions given by a registered dietitian or in a “usual” care program, which included one group meeting and two follow-up mailings. Topics focused on nutrition and exercise interventions. The intensive intervention participants had significantly greater decreases in HbA1c (–1.6 compared to –2.4 percent, p < 0.01) and an average of 2 to 2.5-kg reduction in weight (p = 0.006) compared to controls (Agurs-Collins et al., 1997).
Impact of the Intensity of Nutrition Intervention on Glycemic Control
Franz and associates (1995) completed a randomized trial in 179 persons, 38 to 76 years of age, with type 2 diabetes, comparing the usual nutrition care of one visit to a more intensive nutrition intervention of at least three visits led by a dietitian. The results demonstrated that any nutrition intervention provided by dietitians resulted in significant improvements in medical and clinical outcomes, with FPG decreasing by 50 to 100 mg/dL and HbA1c dropping by 1 to 2 percentage points. Both groups demonstrated improvement in diabetes control, with the more intensive nutrition intervention reducing FPG by 10.5 percent and the usual care by 5.3 percent. A similarly treated but nonrandomized control group who had no contact with a dietitian resulted in HbAlc levels showing no improvement during the same 6-month period of study (8.2 versus 8.4 percent) (Franz et al., 1995). In a prospective randomized trial, Kulkarni et al. (1998) also compared the use of a more intensive nutrition intervention in patients with type 1 diabetes to a control group who received standard nutrition intervention. At 3 months, the HbA1c improved in 88 percent of the participants who had received the more intensive nutrition intervention and in 53 percent of those receiving the standard nutrition intervention. The patients who received the more intensive nutrition intervention also achieved greater decrements in HbA1c levels than the usual care patients (–1.00 versus –0.33, p < 0.05). Both of these studies demonstrate that regardless of the intensity of the nutrition intervention, improvements in blood glucose levels can be achieved with nutrition therapy. In addition, these studies indicate that when practice guidelines are used, increasing the intensity of the nutrition therapy by both time spent and the number of visits, greater improvements in glycemic control result.
Bitzen and colleagues (1988) studied the effect of dietary intervention in 38 hyperglycemic patients who had never been treated by diet or medication (insulin or oral hypoglycemic agents). The participants had a mean age of 63 years. Each received a standardized meal plan by a nurse and weight reduction was advocated for all participants who were above ideal body weight (36 of 38 participants). The education was reinforced at 2- to 3-week intervals over a 10-week period. Each participant also received at least one home visit during the study period. After 10 weeks, 82 percent of participants were found to have significantly reduced both fasting blood glucose (148 mg/dL to 117 mg/dL, p < 0.001) and HbA1c (7.6 percent to 6.7 percent, p < 0.001).
PROVIDERS OF NUTRITION THERAPY FOR DIABETES
In the studies cited above, the formats for interventions varied from multiple individualized visits with dietitians to group sessions with an interdisciplinary team that included a nutrition professional. The DCCT clearly demonstrated the value of a multidisciplinary team in the care of patients with diabetes. Health professionals who contribute to the management of patients with diabetes include physicians, nurses, dietitians, pharmacists, podiatrists, exercise specialists, and social workers. In the management of care for elderly persons, the inclusion of a health professional with particular expertise in the care of elderly persons would be optimal (Fonseca and Wall, 1995).
Prior to results of the DCCT in 1992, data had been less clear regarding the impact of specific nutrition interventions. This, in part, was due to the role of the dietitian in diabetes management intensifying given the demonstrated need for dietary adherence in the DCCT. Since this landmark trial, dietitians have become more focused on individualizing nutrition therapy for patients with diabetes (Delahanty et al., 1993).
The individualized approach requires changes in the lifestyle and goals of each patient and can result in complex dietary interventions. Individualization involves a knowledge of food as it relates to culture, nutrient composition, and meal preparation. For this reason, the American Diabetes Association (1999b) has recommended that a registered dietitian, knowledgeable and skilled in implementing nutritional interventions, be the team member providing nutrition education. In addition, the American Diabetes Association (1999c) has also recommended that education be conducted in the outpatient or home setting because of less frequent and shorter acute care admissions for patients with diabetes.
MEDICARE REIMBURSEMENT FOR DIABETES SELF-MANAGEMENT TRAINING
Prior to July 1, 1998, Medicare Part B covered diabetes education only if provided to registered patients of hospital outpatient departments. These diabetes education programs were required to address diet, exercise, and blood glucose self-monitoring; establish treatment plans for insulin-dependent patients; and motivate patients to manage their conditions. Services could be provided in group or individual sessions. Like other hospital outpatient services, reimbursement was on a “reasonable cost” basis.
Section 4105(a) of the Balanced Budget Act of 1997 added a new benefit to the Medicare program for diabetes self-management training services. This legislation provided coverage for educational and training
services furnished in an outpatient setting by qualified personnel to patients with diabetes, if a physician certifies that such services are needed as part of a comprehensive plan of care. The services are paid under the Medicare physician fee schedule in amounts determined by the Secretary of Health and Human Services. The law specifies that payment may be made to “certified providers” who meet quality standards as determined through regulation, and who also are eligible to receive payment for providing other services to Medicare beneficiaries.
The new benefit has been partially implemented since July 1, 1998. Final implementation is expected early in 2000. In the interim, diabetes self-management training programs that meet the National Standards for Diabetes Self-Management Education Programs and are recognized by the American Diabetes Association, or programs that were receiving reimbursement, are considered to meet the requirements for Medicare coverage. As of October 1999, nationwide there were a total of 978 diabetes self-management education programs sites recognized by the American Diabetes Association. There are, however, widespread rural areas in which access to approved diabetes self-management training is severely limited.
To be an approved provider of diabetes self-management training services, a program must meet certain quality standards. Standards proposed by the Health Care Financing Administration include, among other things, that training be conducted by a team consisting of at least a registered dietitian and a CDE (although for an initial 3-year period a nurse may substitute for the CDE) (HCFA, 1999). Training must address 15 subject areas, including nutrition and the relationships among nutrition, exercise, medication, and blood glucose levels.
The proposed regulations would allow reimbursement for 10 hours of training during a 12-month period and one follow-up training session in each subsequent year. In general, training is to be in group sessions, although individual sessions would be allowed under certain circumstances (e.g., when no group session is available) or with certification that the patient has special needs (e.g., physical impairments, severe language challenges). Patients eligible for the initial 10 training sessions would include those who, within a year before referral, (1) experienced new onset diabetes, (2) had poor glycemic control, (3) experienced a change in medication or use of insulin, (4) had high risk for complications from poor glycemic control, or (5) had experienced certain complications of the foot, eye, or kidney.
Under the proposed rule, entities eligible to provide diabetes self-management training programs include settings such as hospitals, renal dialysis facilities and clinics, and certain independent practitioners who by current law are eligible to receive Medicare reimbursement. These
health professionals include physicians, advanced practice nurses, clinical social workers, psychologists, nurse midwives, and pharmacists. Ironically, at present, the current regulation does not allow the specific health professionals who are required to provide the service (dietitians and CDEs) to bill and receive reimbursement for their services.
Payment for diabetes self-management under the Medicare physician fee schedule is proposed to be $32.62 for group sessions and $55.41 for individual sessions in 1999 (adjusted for geographic variation according to Medicare fee schedule rules). Medicare deductible and coinsurance requirements would apply; thus beneficiaries would pay 20 percent of the proposed amounts, if they had satisfied the $100 annual Part B deductible.
There is a distinct need for repeated training throughout the life of a person with diabetes. The DCCT showed that the diet adherence of a patient occurs in peaks and valleys (DCCT Research Group, 1993). The ability to attain adequate control to prevent costly complications requires continued attention to changes in the severity of the disease, weight, life style, and age. Corrective nutritional education is often necessary.
LIMITATIONS OF DATA AND FUTURE RESEARCH NEEDS
Although a number of studies support the usefulness of nutrition therapy in helping patients attain better control of diabetes and improving outcomes, the number of randomized, controlled trials that specifically explore this question are few. In addition, most of these studies involve nutritional intervention as part of an overall team approach to diabetes education. Therefore, it is not possible to dissect out the specific benefit of the nutritional intervention as a single component of therapy. In addition, it is seldom clear from the studies what type of provider is needed to effect a positive nutritional intervention in patients with diabetes. It is important to extend these studies so that the best provider mix and intensity of intervention can be determined. Additional studies focusing on special populations, such as the elderly and cultural minorities, are also indicated. There is a need for more definitive research on group versus individual formats, the number of encounters and methods needed to achieve improved clinical outcomes in weight, HgA1c levels, lipid levels, blood pressure, and patient satisfaction.
Diabetes mellitus is one of the most prevalent diseases among the U.S. population. This is especially true in the elderly, where nearly 18.4 percent of persons older than 65 have diabetes (American Diabetes Asso-
ciation, 1997). There is reasonable evidence from randomized clinical trials that nutrition intervention as part of overall diabetes education improves blood glucose and HbA1c levels in persons with diabetes, including data in substantial numbers of individuals over age 65. Although nutrition therapy is best carried out when a patient is first diagnosed, it appears to be effective at any time during the disease process and refresher therapy may be of value.
The American Diabetes Association, other national diabetes organizations, and the World Health Organization all support a recommendation for nutrition therapy in patients with diabetes mellitus.
The committee recommends that individualized nutrition therapy, provided by a registered dietitian, be a covered benefit as part of the multidisciplinary approach to the management of diabetes which includes diet, exercise, medications, and blood glucose monitoring. This recommendation is consistent with that of the American Diabetes Association (1999a).
Summary of Evidence: Nutrition Therapy for Diabetes
Recommended as part of the standard of care by the American Diabetes Association (1999a) and the World Health Organization (1994)
Supportive evidence (Agurs-Collins et al., 1997; Bitzen et al., 1988; Delahanty and Halford, 1993; Franz et al., 1995; García and Suárez, 1996; Gilden et al., 1989; Glasgow et al., 1992; Kulkarni et al., 1998)
Reasonable (DCCT Research Group, 1993; UKPDS Group, 1998)
Meta-analyses of trials:
Supportive evidence (Brown, 1988, 1990; Padgett et al., 1988)
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