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Sumamo E, Ha C, Korownyk C, et al. Lifestyle Interventions for Four Conditions: Type 2 Diabetes, Metabolic Syndrome, Breast Cancer, and Prostate Cancer [Internet]. Rockville (MD): Agency for Healthcare Research and Quality (US); 2011 May 26.
This publication is provided for historical reference only and the information may be out of date.
Lifestyle Interventions for Four Conditions: Type 2 Diabetes, Metabolic Syndrome, Breast Cancer, and Prostate Cancer [Internet].
Show detailsThe Coverage and Analysis Group at the Centers for Medicare and Medicaid Services requested this report from The Technology Assessment Program at the Agency for Healthcare Research and Quality (AHRQ). AHRQ assigned this report to the University of Alberta Evidence-based Practice Center (Contract Number: 290-2007-10021-I).
Background
Chronic diseases are the major cause of death and disability worldwide. The World Health Organization (WHO) reported that 88 percent of deaths in the United States in 2002 were attributable to chronic disease.1 Heart disease, cancer, and stroke alone accounted for 55 percent of all deaths in the U.S. in 2005.28
Prevention of the onset or progression of chronic disease is often promoted as the gold standard1 although the optimal interventions to achieve this have not been well documented in the literature. In particular, the benefit of lifestyle interventions in the prevention of chronic disease progression or recurrence has not been fully established.
A number of lifestyle behaviors have been identified as contributors to overall morbidity and mortality of chronic disease. Among these, physical activity and diet have been identified as two modifiable risk factors that may impact onset or progression of disease. The evidence for this comes largely from population based studies which report that adhering to a healthier lifestyle, including dietary and physical components, resulted in a lower risk of all-cause mortality. A 10-year cohort study reported that adhering to a Mediterranean diet and physical activity among other modifiable risk factors resulted in lower risk of all-cause mortality, including mortality from coronary heart disease (CHD), cardiovascular disease (CVD), and cancer.29 Other longitudinal studies also report that a healthy lifestyle at older ages is related to a delay in the deterioration of health status and a reduced mortality risk.30
Ecological data further suggest that improved dietary intake has been beneficial in decreasing the burden of chronic disease, particularly CHD.2–4 A recent systematic review supports this association.5
Despite the demonstrated benefit of improved diet and physical activity in the prevention of certain chronic diseases, the benefits of lifestyle modifications in preventing progression or recurrence of disease is not as well documented. In addition, it remains unclear if additional lifestyle interventions beyond diet and physical activity have proven benefit, how effective interventions are in modifying risk factors, and which diseases in the spectrum of chronic disease, if any, would benefit.
In theory, lifestyle interventions have significant potential for benefit, as more than one-third of all adults do not meet recommendations for aerobic physical activity based on the 2008 Physical Activity Guidelines for Americans.31 Dietary habits are not much better. Only 24 percent of American adults reported eating five or more servings of fruits and vegetables per day32 despite evidence from cohort studies of an inverse association between fruit and vegetable intake and risk for both CHD33 and stroke.34 Finally, obesity has become a major health concern. In the U.S. one in every three adults is obese.35 Large prospective cohort studies have shown that the risk of death from all causes, CVD, cancer, and other diseases increases throughout the range of moderate and severe overweight persons.36,37
Magnitude and Importance of Conditions
Type 2 Diabetes
Type 2 diabetes is defined as a metabolic disorder that is characterized by high blood glucose in the context of insulin resistance and relative insulin deficiency.38 There are an estimated 23.6 million people in the U.S. with diabetes; 90 to 95 percent of these have type 2 diabetes. The total health care costs associated with diabetes in the U.S. in 2007 was estimated to be $174 billion.6 The prevalence of self-reported diabetes increased by 49 percent over a 10-year period in the U.S., from 4.9 percent in 1990 to 7.3 percent in 2000.39 Global estimates of diabetes prevalence suggest that without significant intervention, the burden of diabetes will continue to grow significantly in the next few decades.40
Type 2 diabetes is a major cause of morbidity and mortality. Diabetes was the seventh leading cause of death in the U.S. in 20066 and CVD accounted for more than 65 percent of all diabetic deaths.7 Diabetes is also the leading cause of kidney failure, nontraumatic lower-extremity amputations, and blindness among adults in the U.S.8
With regard to improving overall morbidity and mortality, there is good evidence that improving glycemic control decreases the risk of microvascular complications41 while the impact on macrovascular outcomes is less clear.42–44 A recent study suggested that early intensive glycemic control may improve macrovascular outcomes over the long term.45 Tight blood pressure control has been demonstrated to decrease the risk of microvascular and macrovascular disease in patients with type 2 diabetes.46
Obesity or increased body mass index (BMI) is one of the strongest predictors in the development of type 2 diabetes,47–52 and is also an independent risk factor for CVD. Research suggests that patients with diabetes with increased weight have an increased lifetime risk of CVD.53,54 A recent review demonstrated that weight loss in individuals with type 2 diabetes led to significant reductions in a number of CVD risk factors.55 Furthermore, evidence from retrospective chart reviews and observational studies suggests that reductions in weight significantly decrease premature mortality in diabetic patients.56,57
With regard to dyslipidemia, plasma values for low-density lipoprotein (LDL) cholesterol have been reported to be a predictor of cardiovascular events in patients with diabetes. Patients with a plasma level of LDL cholesterol of approximately 3.89 mmol/L (150 mg/dL) are at a 2-fold greater risk for experiencing a cardiovascular event than the diabetic patient whose plasma value for LDL cholesterol is 1.81 mmol/L (70 mg/dL). A number of trials have demonstrated that lipid lowering therapy, regardless of baseline levels, results in decreased cardiovascular events and mortality in diabetic patients.58,59
Participation in regular, moderate intensity physical activity has been reported to decrease glycosylated hemoglobin (HbA1c)60,61 and is associated with improvements in cardiovascular risk profile.62 More importantly, low cardiorespiratory fitness and physical inactivity are independent predictors of all-cause mortality,63 whereas increased physical activity, including regular walking, has been associated with substantially reduced risk for cardiovascular events in individuals with type 2 diabetes.64
Metabolic Syndrome
The metabolic syndrome is defined as a constellation of interrelated metabolic risk factors that directly promote the development of CVD and type 2 diabetes. The most widely recognized metabolic risk factors are dyslipidemia, elevated plasma glucose, and hypertension. Significant debate exists regarding the clinical utility of metabolic syndrome to predict CVD and type 2 diabetes. Prediabetes, which includes impaired fasting glucose (IFG) and impaired glucose tolerance (IGT), has been suggested to be equally effective in identifying those at risk of developing type 2 diabetes.
Diagnostic criteria for metabolic syndrome have evolved over the years. The WHO task force on diabetes first suggested insulin resistance as the dominant cause of the metabolic syndrome in 1998.65 In 2001, alternate criteria for the diagnosis of the syndrome were introduced by the National Cholesterol Education Program (NCEP) Adult Treatment Panel III (ATP III). ATP III criteria made the presence of three of the following five factors the basis for diagnosing metabolic syndrome: abdominal obesity, elevated triglycerides, reduced HDL-C (high density lipoproteins-cholesterol), elevated blood pressure, and IFG.66 The most current criteria for the metabolic syndrome in the U.S. comes from American Heart Association (AHA)/National Heart, Lung, and Blood Institute (NHLBI) update of the NCEP criteria. The criteria maintain the ATP III criteria except for minor modifications in cut off values.67
The evolving definition of metabolic syndrome has resulted in some inconsistency in the literature. Therefore, our operational definition of metabolic syndrome included metabolic syndrome, insulin resistance, prediabetes, IFG, IGT, syndrome X, dysmetabolic syndrome X, and Reaven syndrome. Our goal was to include populations identified to be at increased risk of developing CVD and/or type 2 diabetes. One recent meta-analysis including 43 cohorts (172,573 individuals) reported that NCEP-defined metabolic syndrome conveyed a relative risk (RR) of 1.78 for CVD events and death.13 Other data suggest that there is little or no association with metabolic syndrome and vascular risk in elderly populations.68 In addition, the diagnosis of metabolic syndrome has been reported to increase the risk for type 2 diabetes by about 2-fold.69 However, several studies have shown that fasting glucose concentration is as good, if not better, than metabolic syndrome in predicting onset of type 2 diabetes.68,70,71
IFG and IGT are frequently associated with metabolic abnormalities. One meta-analysis reported that compared with normoglycemic people, the RR for diabetes in people with IGT was 6.35 (95% CI: 4.87, 7.82), and 4.66 (95% CI: 2.47, 6.85) for IFG.72 In addition, IFG and IGT are associated with a modest increase in the risk for CVD (RR = 1.2).73
Approximately 64 million or 25 percent of adults in the U.S. were estimated to have metabolic syndrome in 2000.9 More recently, the Centers for Disease Control suggests that 34 percent of adults in the U.S. met the diagnostic criteria of metabolic syndrome between 2003–2006.12 As of 2011, the American Diabetes Association estimated that 57 million people in the U.S. had prediabetes,10 many of whom would overlap with metabolic syndrome.
Many risk factors for the development of metabolic syndrome or prediabetes have been proposed, one of which is obesity11 which has increased in incidence alongside the metabolic syndrome over the past decade.12,74 Additional risk factors include increasing age12,13 and physical inactivity.14
Since patients may be at high risk of developing diabetes for a number of reasons, proposed strategies for reducing cardiovascular risk involve the management of multiple risks. Lifestyle changes have traditionally been encouraged as first-line management,75 particularly with regards to the modifiable underlying risk factors76 including obesity77,78 and physical inactivity.
Breast Cancer
Breast cancer is defined as the development of malignant cells in the breast which usually originate from the ducts or lobules of the breast. The National Cancer Institute estimates that in 2010 there will be 209,060 new cases of breast cancer diagnosed, with 40,230 deaths.15 Based on current incidence rates, one out of eight women in the U.S. will be diagnosed with breast cancer during their lifetime. Survival and recurrence rates depend on a number of factors including stage of the cancer at diagnosis.
Estimates of 5-year cumulative incidence of recurrence of early-stage breast cancer following polychemotherapy regimens range from 25 percent (age 50) to 29 percent (age 50–69), rising to 36 to 44 percent by 10 years, Recurrence rates are lower for node-negative breast cancer.15
Risk factors for the recurrence of breast cancer have not been well delineated. Many epidemiological studies suggest a correlation with obesity and increased incident breast cancer risk.16–18 The Women’s Health Initiative observational study found that women weighing more than 82.2 kg had a relative risk of breast cancer of 2.85 (95% CI: 1.81, 4.49) compared with those weighing less than 58.7 kg.79 There is also a body of epidemiological evidence suggesting that increased physical activity reduces incident breast cancer.19 A recent systematic review found that physical activity could reduce the incidence of breast cancer in postmenopausal women by 20 to 80 percent.20
A number of studies have demonstrated the impact of obesity on prognosis in breast cancer.80 A recent systematic review of 43 studies reported a pooled hazard ratio (HR) of 1.33 (95% CI: 1.21, 1.47) for breast cancer specific survival in obese versus non-obese women.81 The benefit of weight loss on prevention of breast cancer recurrence or survival has not been demonstrated.
Some studies have shown a reduction in overall mortality with increased physical activity after breast cancer diagnosis.82–84 Decreased breast cancer recurrence and improved breast cancer specific survival have not been as well addressed, however, a recent systematic review of six studies reported that post-diagnosis physical activity reduced breast cancer deaths by 34 percent (HR = 0.66, 95% CI: 0.57, 0.77), all-cause mortality by 41 percent (HR = 0.59, 95% CI: 0.53, 0.65), and disease recurrence by 24 percent (HR = 0.76, 95% CI: 0.66, 0.87).84 Exercise has also been shown to improve quality of life in breast cancer survivors.85
The role of nutrition in preventing recurrence of breast cancer remains unclear.86 Two recent randomized controlled trials (RCTs) reported conflicting results in recurrence of breast cancer with a low fat diet.87,88
Evidence of benefit of individual lifestyle factors in preventing breast cancer recurrence is limited, and at times remains controversial.89 Many questions remain regarding the benefit of comprehensive lifestyle interventions in modifying suspected risk factors and the consequent impact on disease recurrence.
Prostate Cancer
Prostate cancer is defined as a malignant growth of cells in the prostate gland. It is the second leading cause of death of males in the U.S. It is estimated that 217,730 men will be diagnosed with and 32,050 will die of prostate cancer in 2010 in the U.S.21
The impact of lifestyle factors on incidence or recurrence of prostate cancer remains an area of some controversy. While ecologic studies have demonstrated a direct relationship between a country’s prostate cancer-specific mortality rate and average total calories from fat consumed by the country’s population,90,91 results from studies of the association between dietary intake of fruits and vegetables and risk of prostate cancer are not consistent.22–24
A weak association has been reported between BMI and incident prostate cancer,25 and prospective cohort studies have reported a relationship between increased BMI and more advanced prostate cancer or increased prostate cancer mortality.25,92–95 In addition, higher prostate cancer recurrence rates after radical prostatectomy or radiotherapy treatment have been reported in obese patients.96–100 The Cancer Prevention Study suggested that men who lost weight appeared to reduce their risk of prostate cancer.101
Evidence regarding physical activity in the prevention of incident prostate cancer is limited. In a 1997 review of 17 studies, 9 suggested possible benefit, 5 demonstrated no effect, and 3 reported increased risk of prostate cancer with increased exercise.26 A 2004 review suggested a probable inverse relationship between physical activity and prostate cancer incidence although the existence of conflicting evidence was noted.27 Furthermore, two large prospective cohort studies reported conflicting results regarding the benefits of exercise in prostate cancer. One study of 293,902 men found no difference in prostate cancer risk with increased exercise,102 while the other (n = 45,887) suggested a 20 percent reduction in prostate cancer incidence with increased physical activity.103
Evidence regarding effect of physical activity on recurrence or overall survivorship is lacking. One cohort study of 47,620 men suggested that among those 65 years or older vigorous physical activity was associated with decreased risk of death from cancer.104 Studies looking at the benefit of physical activity on other outcomes, including quality of life, are more prevalent. A recent systematic review of physical activity in prostate cancer survivors reported evidence of effect of physical activity on muscular fitness, physical functioning, fatigue, and health-related quality of life although it recognized the current limitations of available evidence.105
Although PSA has a number of limitations, it is generally viewed as a biomarker of disease progression in patients with a history of prostate cancer in which elevated levels may indicate early recurrence of the disease.106
The American Cancer Society recommends that men who have been diagnosed with prostate cancer should consume diets that are rich in vegetables and fruit and low in saturated fat, and pursue a physically active lifestyle. This recommendation is likely based on the assumption that there are substantial other benefits to these recommendations, most prominently decreasing CVD risk, which is the major cause of death in prostate cancer survivors.107
Objective of the Report
The objective of this report was to identify and synthesize the available evidence regarding the effect of lifestyle interventions on the management of four common chronic disease conditions: type 2 diabetes, metabolic syndrome, breast cancer, and prostate cancer. For the purpose of this review, lifestyle interventions were defined as any intervention that included an exercise component, a dietary component (not necessarily weight loss), and at least one other element, including but not limited to, counseling, stress management, behavior modification, weight loss, smoking cessation or risk factor modification.
Key Questions
- What is the evidence on the effectiveness of lifestyle interventions for type 2 diabetes mellitus, metabolic syndrome, breast cancer, and prostate cancer?
- What is the generalizability of the evidence to the Medicare population (> 65 years)?
- What is the evidence on whether specific components of the interventions, composition of the team, and/or patient characteristics contribute to better outcomes?
Analytic Framework
Figure 1 illustrates an analytic framework used to guide assessment of studies involving lifestyle interventions. The figure shows how lifestyle interventions will result in the prevention of progression to additional medication or insulin treated diabetes or future related morbidities in patients with type 2 diabetes, the prevention of progression to diabetes, heart disease, or stroke in those with metabolic syndrome, and the prevention of cancer recurrence in people previously treated for breast and prostate cancer. Adverse reactions that are directly related to the lifestyle intervention are unlikely, but are included in the framework.
Figure 1
Analytic framework for lifestyle interventions.
- Introduction - Lifestyle Interventions for Four ConditionsIntroduction - Lifestyle Interventions for Four Conditions
- Hyperthermic Isolated Limb Perfusion - Madame Curie Bioscience DatabaseHyperthermic Isolated Limb Perfusion - Madame Curie Bioscience Database
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