Dataset Information

Six-Year Incidence and Progression of Age-Related Macular Degeneration in Kenya: Nakuru Eye Disease Cohort Study.

ABSTRACT:

Importance

The incidence of age-related macular degeneration (AMD) is unknown in Africa.

Objective

To estimate the 6-year cumulative incidence and progression of AMD in older adults (≥50 years old) in Nakuru, Kenya.

Design, setting, and participants

This study assessed a population-based cohort with 6-year follow-up of 4414 participants who had a complete assessment. Random cluster sampling with probability proportionate to size procedures was used to select a representative, cross-sectional sample of adults 50 years and older from January 26, 2007, through November 11, 2008. A 6-year follow-up was undertaken from January 7, 2013, through March 12, 2014. On both occasions, a comprehensive ophthalmic examination was performed that included logMAR visual acuity, digital retinal photography, and grading of images at Moorfields Eye Hospital Reading Centre. Data were collected on general health and risk factors.

Main outcomes and measures

Incident AMD in participants with no AMD at baseline and progression from early to late AMD.

Results

A total of 1453 of the 2900 individuals (50.1%) at risk for AMD were followed up after 6 years (mean [SD] age, 60.7 [8.2] years; 635 female [49.5%]; 799 Kikuyu [62.3%], 324 Kalenjin [25.3%], and 159 other [12.4%]); 1282 had data on AMD status at follow-up. Of these, 202 developed early AMD, and no participants developed late AMD. The 6-year weighted (for loss to follow-up) cumulative incidence of early AMD was 164.2 per 1000 persons (95% CI, 136.7-195.9 per 1000 persons). Two individuals with baseline early AMD from the 142 at risk had developed late AMD at follow-up, with a 6-year cumulative incidence of progression from early to late AMD of 24.5 per 1000 persons (95% CI, 5.0-111.7 per 1000 persons). Cumulative incidence of AMD increased with age (≥80 years old vs 50-59 years old: 1.8; 95% CI, 0.9-3.5) and was higher in women (female vs male: 1.6; 95% CI, 1.2-2.1) and persons with diabetes (diabetes vs no diabetes: 1.7; 95% CI, 1.0-2.8).

Conclusions and relevance

In Kenya, more than 100 000 estimated new cases of AMD, mainly early AMD, will develop every year in individuals 50 years or older, although a 50% loss to follow-up and wide CIs for progression to late AMD limit definitive conclusions from these findings.

SUBMITTER: Bastawrous A

PROVIDER: S-EPMC5710264 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundDiseases of the posterior segment of the eye, including age-related macular degeneration (AMD), have recently been recognised as the leading or second leading cause of blindness in several African countries. However, prevalence of AMD alone has not been assessed. We hypothesized that AMD is an important cause of visual impairment among elderly people in Nakuru, Kenya, and therefore sought to assess the prevalence and predictors of AMD in a diverse adult Kenyan population.Methods and findingsIn a population-based cross-sectional survey in the Nakuru District of Kenya, 100 clusters of 50 people 50 y of age or older were selected by probability-proportional-to-size sampling between 26 January 2007 and 11 November 2008. Households within clusters were selected through compact segment sampling. All participants underwent a standardised interview and comprehensive eye examination, including dilated slit lamp examination by an ophthalmologist and digital retinal photography. Images were graded for the presence and severity of AMD lesions following a modified version of the International Classification and Grading System for Age-Related Maculopathy. Comparison was made between slit lamp biomicroscopy (SLB) and photographic grading. Of 4,381 participants, fundus photographs were gradable for 3,304 persons (75.4%), and SLB was completed for 4,312 (98%). Early and late AMD prevalence were 11.2% and 1.2%, respectively, among participants graded on images. Prevalence of AMD by SLB was 6.7% and 0.7% for early and late AMD, respectively. SLB underdiagnosed AMD relative to photographic grading by a factor of 1.7. After controlling for age, women had a higher prevalence of early AMD than men (odds ratio 1.5; 95% CI, 1.2-1.9). Overall prevalence rose significantly with each decade of age. We estimate that, in Kenya, 283,900 to 362,800 people 50 y and older have early AMD and 25,200 to 50,500 have late AMD, based on population estimates in 2007.ConclusionsAMD is an important cause of visual impairment and blindness in Kenya. Greater availability of low vision services and ophthalmologist training in diagnosis and treatment of AMD would be appropriate next steps. Please see later in the article for the Editors' Summary.

Project description:PurposeTo report the natural history of untreated neovascular age-related macular degeneration (nAMD) regarding subsequent macular atrophy.DesignProspective cohort within a randomized, controlled trial of oral micronutrient supplements.ParticipantsAge-Related Eye Disease Study (AREDS) participants (55-80 years) who demonstrated nAMD during follow-up (1992-2005), prior to anti-vascular endothelial growth factor (VEGF) therapy.MethodsColor fundus photographs were collected at annual study visits and graded centrally for late age-related macular degeneration (AMD). Incident macular atrophy after nAMD was examined by Kaplan-Meier analysis and proportional hazards regression.Main outcome measuresIncident macular atrophy after nAMD.ResultsOf the 4757 AREDS participants, 708 eyes (627 participants) demonstrated nAMD during follow-up and were eligible. The cumulative risks of incident macular atrophy after untreated nAMD were 9.6% (standard error, 1.2%), 31.4% (standard error, 2.2%), 43.1% (standard error, 2.6%), and 61.5% (standard error, 4.3%) at 2, 5, 7, and 10 years, respectively. This corresponded to a linear risk of 6.5% per year. The cumulative risk of central involvement was 30.4% (standard error, 3.2%), 43.4% (standard error, 3.8%), and 57.0% (standard error, 4.8%) at first appearance of atrophy, 2 years, and 5 years, respectively. Geographic atrophy (GA) in the fellow eye was associated with increased risk of macular atrophy (hazard ratio [HR], 1.70; 95% confidence interval [CI], 1.17-2.49; P = 0.006). However, higher 52-single nucleotide polymorphism AMD genetic risk score was not associated with increased risk of macular atrophy (HR, 1.03; 95% CI, 0.90-1.17; P = 0.67). Similarly, no significant differences were observed according to SNPs at CFH, ARMS2, or C3.ConclusionsThe rate of incident macular atrophy after untreated nAMD is relatively high, increasing linearly over time and affecting half of eyes by 8 years. Hence, factors other than anti-VEGF therapy are involved in atrophy development, including natural progression to GA. Comparison with studies of treated nAMD suggests it may not be necessary to invoke a large effect of anti-VEGF therapy on inciting macular atrophy, although a contribution remains possible. Central involvement is present in one third of eyes at the outset (similar to pure GA) and increases linearly to half at 3 years.

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