Association of Metformin With the Development of Age-Related Macular Degeneration

Importance

Age-related macular degeneration (AMD) is a leading cause of blindness with no treatment available for early stages. Retrospective studies have shown an association between metformin and reduced risk of AMD.

Objective

To investigate the association between metformin use and age-related macular degeneration (AMD).

Design, Setting, and Participants

The Diabetes Prevention Program Outcomes Study is a cross-sectional follow-up phase of a large multicenter randomized clinical trial, Diabetes Prevention Program (1996-2001), to investigate the association of treatment with metformin or an intensive lifestyle modification vs placebo with preventing the onset of type 2 diabetes in a population at high risk for developing diabetes. Participants with retinal imaging at a follow-up visit 16 years posttrial (2017-2019) were included. Analysis took place between October 2019 and May 2022.

Interventions

Participants were randomly distributed between 3 interventional arms: lifestyle, metformin, and placebo.

Main Outcomes and Measures

Prevalence of AMD in the treatment arms.

Results

Of 1592 participants, 514 (32.3%) were in the lifestyle arm, 549 (34.5%) were in the metformin arm, and 529 (33.2%) were in the placebo arm. All 3 arms were balanced for baseline characteristics including age (mean [SD] age at randomization, 49 [9] years), sex (1128 [71%] male), race and ethnicity (784 [49%] White), smoking habits, body mass index, and education level. AMD was identified in 479 participants (30.1%); 229 (14.4%) had early AMD, 218 (13.7%) had intermediate AMD, and 32 (2.0%) had advanced AMD. There was no significant difference in the presence of AMD between the 3 groups: 152 (29.6%) in the lifestyle arm, 165 (30.2%) in the metformin arm, and 162 (30.7%) in the placebo arm. There was also no difference in the distribution of early, intermediate, and advanced AMD between the intervention groups. Mean duration of metformin use was similar for those with and without AMD (mean [SD], 8.0 [9.3] vs 8.5 [9.3] years; P = .69). In the multivariate models, history of smoking was associated with increased risks of AMD (odds ratio, 1.30; 95% CI, 1.05-1.61; P = .02).

Conclusions and Relevance

These data suggest neither metformin nor lifestyle changes initiated for diabetes prevention were associated with the risk of any AMD, with similar results for AMD severity. Duration of metformin use was also not associated with AMD. This analysis does not address the association of metformin with incidence or progression of AMD.

The Impact of Physical Activity on the Prevention of Type 2 Diabetes: Evidence and Lessons Learned From the Diabetes Prevention Program, a Long-Standing Clinical Trial Incorporating Subjective and Objective Activity Measures

OBJECTIVE

Across the Diabetes Prevention Program (DPP) follow-up, cumulative diabetes incidence remained lower in the lifestyle compared with the placebo and metformin randomized groups and could not be explained by weight. Collection of self-reported physical activity (PA) (yearly) with cross-sectional objective PA (in follow-up) allowed for examination of PA and its long-term impact on diabetes prevention.

RESEARCH DESIGN AND METHODS

Yearly self-reported PA and diabetes assessment and oral glucose tolerance test results (fasting glucose semiannually) were collected for 3,232 participants with one accelerometry assessment 11-13 years after randomization (n = 1,793). Mixed models determined PA differences across treatment groups. The association between PA and diabetes incidence was examined using Cox proportional hazards models.

RESULTS

There was a 6% decrease (Cox proportional hazard ratio 0.94 [95% CI 0.92, 0.96]; P < 0.001) in diabetes incidence per 6 MET-h/week increase in time-dependent PA for the entire cohort over an average of 12 years (controlled for age, sex, baseline PA, and weight). The effect of PA was greater (12% decrease) among participants less active at baseline (<7.5 MET-h/week) (n = 1,338) (0.88 [0.83, 0.93]; P < 0.0001), with stronger findings for lifestyle participants. Lifestyle had higher cumulative PA compared with metformin or placebo (P < 0.0001) and higher accelerometry total minutes per day measured during follow-up (P = 0.001 and 0.047). All associations remained significant with the addition of weight in the models.

CONCLUSIONS

PA was inversely related to incident diabetes in the entire cohort across the study, with cross-sectional accelerometry results supporting these findings. This highlights the importance of PA within lifestyle intervention efforts designed to prevent diabetes and urges health care providers to consider both PA and weight when counseling high-risk patients.

Diet quality, weight loss, and diabetes incidence in the Diabetes Prevention Program (DPP)

BACKGROUND

We evaluated whether diet quality is a predictor of weight loss and reduced diabetes risk, independent of caloric intake in the Diabetes Prevention Program (DPP) cohort, a randomized clinical trial of adults at risk for diabetes.

METHODS

This secondary analysis included 2914 participants with available data (964 intensive lifestyle (ILS), 977 metformin, 973 placebo). Dietary intake was assessed using a 117-item food frequency questionnaire. Diet quality was quantified using the Alternative Healthy Eating Index 2010 (AHEI). AHEI ranges from 0 to 110, with higher scores corresponding to higher quality diets. ILS participants had greater improvement (p < 0.001) in AHEI over 1-year (4.2 ± 9.0) compared to metformin (1.2 ± 8.5) and placebo (1.4 ± 8.4). We examined the association between AHEI change and weight change from baseline to 1-year using linear regression, and that between 1-year AHEI change and incident diabetes, using hazard models over an average 3 years follow-up. Models were evaluated within treatment group and adjusted for relevant characteristics including caloric intake, physical activity, BMI and AHEI. Models testing incident diabetes were further adjusted for baseline fasting and 2 h glucose.

RESULTS

An increase in AHEI score was associated with weight loss in ILS [β per 10-point increase (SE) -1.2 kg (0.3, p < 0.001)], metformin [- 0. 90 kg (0.2, p < 0.001)] and placebo [- 0.55 kg (0.2, p = 0.01)]. However, AHEI change was not associated with incident diabetes in any group before or after adjustment for weight change.

CONCLUSIONS

Controlling for weight, diet quality was not associated with diabetes incidence but helps achieve weight loss, an important factor in diabetes prevention.

Provider Preference for Growth Charts in Tracking Children with Obesity

A web-based survey of pediatric care providers revealed differences in their preference for clinical charts that monitor growth in children with obesity. These findings are attributed to pediatric specialty training. Very few providers believe the currently available Centers for Disease Control and Prevention 2000 body mass index-for-age charts adequately track growth in children with obesity.

Abstract A23: Cancer outcomes in the diabetes prevention program outcomes study

Numerous observational studies have reported decreased cancer incidence and cancer-related mortality in patients with diabetes receiving standard doses of metformin. A recent meta-analysis of these studies suggested a 31% reduction in overall cancer incidence, summary relative risk (0.69; 95% confidence interval, 0.52-0.90), in subjects taking metformin as compared with other antidiabetic drugs. Separate meta-analyses of studies that adjusted for BMI or time-related bias suggested an attenuation of this signal, but still showed a significant reduction in cancer incidence. However, studies published to date are limited by the observational nature of the data and the randomized controlled trials that have been used to examine metformin's potential as an anti-cancer agent in patients with diabetes have had insufficient follow-up for cancer endpoints. These data also do not address the cancer risk in non-diabetic populations, in which the cancer preventive potential of metformin is unknown.

The Diabetes Prevention Program (DPP) was a national multi-center, randomized, placebo-controlled clinical trial, which enrolled 3234 participants between 1996 and 1999, designed to investigate whether intensive lifestyle modification or treatment with metformin (850mg twice a day) delayed or prevented the onset of type 2 diabetes in a high risk population. The DPP and its follow up study, the Diabetes Prevention Program Outcomes Study (DPPOS), provide a unique opportunity to examine the role of metformin and lifestyle intervention in reducing cancer incidence in an overweight adult population with impaired glucose regulation, before the onset of diabetes. The National Cancer Institute Division of Cancer Prevention, in collaboration with the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) and the DPPOS investigators, proposed a study to examine the hypothesis that metformin and/or lifestyle intervention can modify total cancer incidence and/or obesity-related cancer incidence (breast, colorectal, endometrium, pancreas, lower esophagus, gall-bladder, and kidney) in DPP/DPPOS participants.

The DPPOS protocol and consent were modified to allow collection of data to support the inclusion of cancer incidence as an endpoint of interest in the study. Participants complete a cancer risk questionnaire that includes family history of cancer, cancer screening activities, and use of aspirin and NSAIDs including dose and frequency. The participants who previously reported a cancer diagnosis, through the SAE reporting process and/or an annual questionnaire, or during a subsequent follow-up visit, are asked to provide physician information to obtain medical records for case adjudication. This protocol will allow for the examination of the effect of metformin and lifestyle intervention on cancer incidence in an initially pre-diabetic population potentially through a median of 20 years of follow-up.

Data from this study will compare incidence of total and obesity-related cancers between the original treatment groups; assess cancer (total and obesity-related) incidence by metformin exposure across all treatment groups, using a “met-years” variable, and explore subgroups to investigate effect modification by sex, age group, race/ethnicity, diabetes status, or weight loss at 1 year or mean weight loss since study baseline.

Citation Format: Brandy M. Heckman-Stoddard, Jill P. Crandall, Sharon L. Edelstein, Richard F. Hamman, Philip C. Prorok, Anne Ryan, Dana Dabelea, Helen P. Hazuda, Edward Horton, Mary A. Hoskin, Susan Jeffries, William C. Knowler, Kieren J. Mather, Susana M. Shapiro, Farzana L. Walcott, Leslie G. Ford. Cancer outcomes in the diabetes prevention program outcomes study. [abstract]. In: Proceedings of the Thirteenth Annual AACR International Conference on Frontiers in Cancer Prevention Research; 2014 Sep 27-Oct 1; New Orleans, LA. Philadelphia (PA): AACR; Can Prev Res 2015;8(10 Suppl): Abstract nr A23.

Short and long-term lifestyle coaching approaches used to address diverse participant barriers to weight loss and physical activity adherence

Background

Individual barriers to weight loss and physical activity goals in the Diabetes Prevention Program, a randomized trial with 3.2 years average treatment duration, have not been previously reported. Evaluating barriers and the lifestyle coaching approaches used to improve adherence in a large, diverse participant cohort can inform dissemination efforts.

Methods

Lifestyle coaches documented barriers and approaches after each session (mean session attendance = 50.3 ± 21.8). Subjects were 1076 intensive lifestyle participants (mean age = 50.6 years; mean BMI = 33.9 kg/m²; 68% female, 48% non-Caucasian). Barriers and approaches used to improve adherence were ranked by the percentage of the cohort for whom they applied. Barrier groupings were also analyzed in relation to baseline demographic characteristics.

Results

Top weight loss barriers reported were problems with self-monitoring (58%); social cues (58%); holidays (54%); low activity (48%); and internal cues (thought/mood) (44%). Top activity barriers were holidays (51%); time management (50%); internal cues (30%); illness (29%), and motivation (26%). The percentage of the cohort having any type of barrier increased over the long-term intervention period. A majority of the weight loss barriers were significantly associated with younger age, greater obesity, and non-Caucasian race/ethnicity (p-values vary). Physical activity barriers, particularly thought and mood cues, social cues and time management, physical injury or illness and access/weather, were most significantly associated with being female and obese (p < 0.001 for all). Lifestyle coaches used problem-solving with most participants (≥75% short-term; > 90% long term) and regularly reviewed self-monitoring skills. More costly approaches were used infrequently during the first 16 sessions (≤10%) but increased over 3.2 years.

Conclusion

Behavioral problem solving approaches have short and long term dissemination potential for many kinds of participant barriers. Given minimal resources, increased attention to training lifestyle coaches in the consistent use of these approaches appears warranted.

Dietary intake in the diabetes prevention program cohort: baseline and 1-year post randomization

PURPOSE

To describe usual dietary intake assessment at baseline and 1-year post-randomization in the ethnically diverse Diabetes Prevention Program cohort.

METHODS

Participants were randomized to Lifestyle Modification, Metformin, or Placebo. Usual diet was assessed by a modified, previously validated food frequency interview.

RESULTS

Complete data were available for 2934 subjects (90.7% of those randomized). Baseline median estimated energy intake was 7676 kJ/d (1828 kcal/d) and 8585 kJ/d (2044 kcal/d) for women and men, respectively. The median percent of energy from fat ranged from 30.6% for Asian American men to 37.5% for American Indian men and women. After 1 year among the Lifestyle group, the median change in total energy and percent energy from fat was -1897 kJ/d (-452 kcal/d) and -6.6%, respectively. For the Metformin and Placebo groups, change in median total energy was -1235 kJ/d (-294 kcal/d) and-1051 kJ/d (-250 kcal/d), respectively, and change in median percent energy from fat was -0.8% and-0.8%, respectively (p < 0.001 for differences between groups, adjusted for gender and ethnicity).

CONCLUSIONS

One-year post-randomization, significant differences in dietary intake were observed in the Lifestyle compared with the Metformin or Placebo group, and these were consistent with the general intent of the DPP lifestyle modification intervention.

Achieving weight and activity goals among diabetes prevention program lifestyle participants

OBJECTIVE

The Diabetes Prevention Program (DPP) showed that intensive lifestyle intervention reduced the risk of diabetes by 58%. This paper examines demographic, psychosocial, and behavioral factors related to achieving weight loss and physical activity goals in the DPP lifestyle participants.

RESEARCH METHODS AND PROCEDURES

Lifestyle participants (n = 1079; mean age = 50.6, BMI = 33.9, 68% female, and 46% from minority groups) had goals of 7% weight loss and 150 min/wk of physical activity. Goal achievement was assessed at the end of the 16-session core curriculum (approximately week 24) and the final intervention visit (mean = 3.2 years) as a function of demographic, psychosocial, and behavioral variables.

RESULTS

Forty-nine percent met the weight loss goal and 74% met the activity goal initially, while 37% and 67%, respectively, met these goals long-term. Men and those with lower initial BMI were more likely to meet activity but not weight loss goals. Hispanic, Asian, and Native Americans were more likely to meet the long-term activity goals, and whites were more likely to meet the initial weight loss goal. In multivariate analyses, meeting the long-term weight loss goal and both activity goals increased with age, while psychosocial and depression measures were unrelated to goal achievement. Dietary self-monitoring was positively related to meeting both weight loss and activity goals, and meeting the activity goal was positively related to meeting the weight loss goal. Participants who met initial goals were 1.5 to 3.0 times more likely to meet these goals long-term.

DISCUSSION

Success at meeting the weight loss and activity goals increased with age. Initial success predicted long-term success. Self-monitoring and meeting activity goals were related to achieving and sustaining weight loss.