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Diabetes: Combined Diet and Physical Activity Promotion Programs to Prevent Type 2 Diabetes Among People at Increased Risk

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What the CPSTF Found

About The Systematic Review

The CPSTF finding is based on evidence from a systematic review of 53 studies that described 66 programs (search period January 1991 - February 2015).

The review was conducted on behalf of the CPSTF by a team of specialists in systematic review methods, and in research, practice and policy related to diabetes prevention and control.

Context

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Summary of Results

Detailed results from the systematic review are available in the CPSTF Finding and Rationale Statement pdf icon [PDF - 684 kB].

The systematic review included 53 studies that described 66 programs.

  • Among populations at increased risk of type 2 diabetes, combined diet and physical activity promotion programs led to improvements in health outcomes and risk factors for type 2 diabetes and cardiovascular disease compared with usual care.
    • The proportion of people who developed type 2 diabetes decreased by a median of 11 percentage points (16 studies).
    • The proportion of people who achieved normal blood sugar (normoglycemia) increased by a median of 12 percentage points (6 studies).
    • Body weight was reduced by an average of 2.2% (24 studies).
    • Fasting blood glucose was reduced (improved) by an average of 2.2 mg/dL (17 studies) and hemoglobin A1c (a measure of long-term glucose levels) was reduced (improved) by an average of 0.08 percentage points (8 studies).
    • Blood pressure (17 studies) and cholesterol levels (13 studies) also were improved.
  • The effect on mortality was unclear. Mortality was reduced by 2 to 10 percentage points (2 studies) or by 0.6 per 1000 person-years (1 study) over 3 to 23 years of follow-up. However, this benefit was statistically significant in only one study, and in that study, only among women.
  • Regardless of program features, almost all programs led to weight loss, reduced risk of diabetes, or both. However, among 12 studies with direct comparisons, more intensive programs (based on features such as number of sessions, individual sessions, and additional personnel) resulted in greater weight loss and lower rates of diabetes than less intensive programs. Across studies, more effective programs provided:
    • Individual (vs. group) exercise sessions,
    • Individual (vs. group) diet sessions, or
    • Diet counselors
  • In studies of programs that used protocols outlined by the U.S. Diabetes Prevention Program (DPP) study or Finnish Diabetes Prevention Study (DPS), or modifications of them, participants lost more weight (3% of initial body weight) than participants in programs not based on DPP or DPS (1.6% of initial body weight). Reductions in risk of developing diabetes were similar between studies of different programs.

Summary of Economic Evidence

Detailed results from the systematic review are available in the CPSTF Finding and Rationale Statement pdf icon [PDF - 684 kB].

An economic review of 28 studies (search period January 1985 - April 2015) shows that combined diet and physical activity promotion programs for people at increased risk for type 2 diabetes are cost-effective. All monetary values reported are in 2013 U.S. dollars.

Cost of programs:

  • All programs: median $653 per participant (12 studies)
  • Group-based programs: median $417 per participant (8 studies)
  • Programs that translated the U.S. DPP into community or primary care settings: median $424 per participant (8 studies)

Cost-effectiveness of the program (from the health system perspective, which included only the direct medical costs of the programs and healthcare costs averted, based on either data collected in actual programs or estimates from simulation models):

  • Cost per quality-adjusted life year (QALY) saved:
    • All programs: median $13,761 (16 studies)
    • Group-based programs: median $1,819 (5 studies)
    • Individual-based programs: median $15,846 (5 studies)
  • Cost per disability-adjusted life year (DALY) averted:
    • $21,195 and $50,707 (2 studies)
  • Cost per life year gained (LYG):
    • Median $2,684 (6 studies)

The variation in program costs per participant is partly explained by the number of sessions, delivery mode of the core sessions (individual vs. group), setting (clinical trial vs. community or primary care), and type of personnel used (health professionals vs. trained laypeople).

The variation in cost-effectiveness is partially explained by variation in cost and effectiveness of the programs, program delivery modes, patient follow-up times, and delivery settings.

Applicability

The CPSTF finding is applicable to men and women in the United States who are at increased risk for type 2 diabetes, regardless of race/ethnicity, socioeconomic level, setting (urban or rural). The finding applies to programs offered through healthcare and community-based settings.

Evidence Gaps

Additional research and evaluation are needed to answer the following questions and fill existing gaps in the evidence base.

  • How does program effectiveness vary by population demographics (e.g., race/ethnicity, SES, educational attainment, age, cognitive or physical disabilities)?
  • How effective are programs delivered via the Internet, email, apps, or social networking?
  • What is the relative effectiveness of individual and group sessions?
  • What are effective structures for the maintenance phase of these programs to help participants continue their improvements to diet and physical activity following completion of the core phase?
  • What are long-term effects of community-based programs on diabetes incidence, weight loss, other diabetes risk factors, morbidity, and mortality?
  • What are recruitment and attrition rates? Why don’t all referred clients follow-up and why do some participants drop out? What are effective strategies to recruit and retain clients?

Economic Review

  • What are the economic costs and benefits of programs implemented in community and primary care settings? Evaluations should include group-based programs delivered by trained laypeople.
  • What are the costs of identifying and recruiting eligible individuals to participate?
  • What are the costs associated with program implementation in community or primary care settings, and how can they be lowered? Costs include start-up costs, costs of program delivery (by program duration and setting), and costs to different stakeholders and society as a whole.
  • What are long-term economic benefits of a program? What are actual heath care expenditures averted in total, by expenditure category? Ideally, an assessment would follow an intervention cohort and its comparison group for a long period of time.

Study Characteristics

  • Programs lasted from three months to six years (median 12 months).
    • The core period lasted between one month and five years (median 6 months).
    • Maintenance periods (in 28 programs) lasted between four and 68 months, with a median of 12 months.
  • Programs provided between 0 (virtual sessions only) and 72 sessions, with a median of 15 sessions.
    • During the core period, there were between 0 (virtual only) and 72 sessions, with a median of 10 sessions.
    • During the maintenance period (in 28 programs), there were between 0 (virtual only) and 24 sessions, with a median of 6 sessions. In some programs, the maintenance period contacts were by telephone or email only.
  • Programs used individual face-to-face meetings (40 programs included individual diet sessions, 41 programs included individual exercise sessions), group meetings (diet: 41 programs, exercise: 39 programs), or both (diet: 24 programs, exercise: 24 programs). Five programs were conducted via web-tools, social networking, email, text messaging, video, or a combination of these, with no in-person sessions.
  • Sessions were led by different combinations of trained diet counselors including dietitians, nutritionists, or others (37 programs); trained exercise counselors including physical trainers or others (26 programs); nurses (15 programs); physicians or psychologists (8 programs); and trained laypeople (13 programs).
  • Programs included specific weight loss goals (42 programs), diet goals (19 programs), and physical activity goals (32 programs).
  • Programs included individually tailored plans for diet (16 programs) and physical activity (23 programs).
  • Studies were conducted in the United States (21 studies), Europe (17 studies), and other countries.

Publications

Pronk NP. Systematic review with meta analysis: structured diet and physical activity programmes provide strong evidence of effectiveness for type 2 diabetes prevention and improvement of cardiometabolic health. Evidence-Based Medicine. 2015.