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.

Novel hMLH1 and hMSH2 germline mutations in African Americans with colorectal cancer

CONTEXT

Germline mutations of the DNA mismatch repair (MMR) genes hMLH1 and hMSH2 have been shown to cosegregate with the colorectal cancer phenotype in multiple hereditary nonpolyposis colorectal cancer (HNPCC) pedigrees. However, the frequency of these mutations among African American patients with colorectal cancer is unknown.

OBJECTIVE

To investigate the frequency of germline alterations of the DNA MMR genes hMLH1 and hMSH2 among African Americans affected by HNPCC and early-age onset colorectal cancer.

DESIGN, SETTING, AND PATIENTS

Forty unrelated African American HNPCC and early-age onset colorectal cancer patients (8 women, 3 men) were identified from the cancer registry at a National Cancer Institute-designated referral center, 11 of whom were available for and agreed to study participation from January 1997 to February 1998. The mean age of the subjects was 44 years. An additional 50 age- and sex-matched African Americans without personal or family history of colorectal, endometrial, ovarian, urinary tract, or upper gastrointestinal tract malignancy were also studied as a polymorphism control population. In all subjects, genomic DNA was amplified by polymerase chain reaction for all hMLH1 and hMSH2 exons and screened using single-strand conformation polymorphism (SSCP) analysis. Samples demonstrating significant SSCP shifts underwent automated nucleotide sequencing analysis.

MAIN OUTCOME MEASURE

Frequency of hMLH1 and hMSH2 germline alterations in the affected and control subjects.

RESULTS

Germline hMLH1 and hMSH2 mutations were detected in 3 (27%) of the African American colorectal cancer probands studied. Each mutation was novel. Two hMLH1 (an A-->T transversion at codon 26 and a GG-->AT substitution across codons 177 and 178) mutations and 1 hMSH2 mutation (a C-->T transition at codon 389) were identified in 3 female study subjects. Six other hMLH1 and hMSH2 alterations were detected but were presumed to be polymorphisms. Neither missense mutation (at codons 26 and 389) was detected in the control population.

CONCLUSIONS

The results of our analysis support an association between the 3 mutations reported and predisposition to colorectal cancer. Further studies are needed to define DNA MMR gene-associated colorectal cancer in African Americans, an understudied population at increased risk of fatal colorectal cancer.

The foster carer experience in Ireland: findings from a postal survey

Findings from a postal survey of foster carers in a region of Ireland are reported. While a majority of the respondents seem broadly contented in their role, it is clear that some are experiencing difficulties of different kinds. Problems experienced by different minorities of these foster carers included concerns with the level of administrative and professional support, worries about being parted from the child, and problems in the relationship with the child's biological parents. Responses on motivations to foster suggest a high level of altruistic motivation. The possible implication of these and other findings are discussed.