Dataset Information

Six-Year Incidence of Blindness and Visual Impairment in Kenya: The Nakuru Eye Disease Cohort Study.

ABSTRACT:

Purpose

To describe the cumulative 6-year incidence of visual impairment (VI) and blindness in an adult Kenyan population. The Nakuru Posterior Segment Eye Disease Study is a population-based sample of 4414 participants aged ?50 years, enrolled in 2007-2008. Of these, 2170 (50%) were reexamined in 2013-2014.

Methods

The World Health Organization (WHO) and US definitions were used to calculate presenting visual acuity classifications based on logMAR visual acuity tests at baseline and follow-up. Detailed ophthalmic and anthropometric examinations as well as a questionnaire, which included past medical and ophthalmic history, were used to assess risk factors for study participation and vision loss. Cumulative incidence of VI and blindness, and factors associated with these outcomes, were estimated. Inverse probability weighting was used to adjust for nonparticipation.

Results

Visual acuity measurements were available for 2164 (99.7%) participants. Using WHO definitions, the 6-year cumulative incidence of VI was 11.9% (95%CI [confidence interval]: 10.3-13.8%) and blindness was 1.51% (95%CI: 1.0-2.2%); using the US classification, the cumulative incidence of blindness was 2.70% (95%CI: 1.8-3.2%). Incidence of VI increased strongly with older age, and independently with being diabetic. There are an estimated 21 new cases of VI per year in people aged ?50 years per 1000 people, of whom 3 are blind. Therefore in Kenya we estimate that there are 92,000 new cases of VI in people aged ?50 years per year, of whom 11,600 are blind, out of a total population of approximately 4.3 million people aged 50 and above.

Conclusions

The incidence of VI and blindness in this older Kenyan population was considerably higher than in comparable studies worldwide. A continued effort to strengthen the eye health system is necessary to support the growing unmet need in an aging and growing population.

SUBMITTER: Bastawrous A

PROVIDER: S-EPMC5102568 | biostudies-literature | 2016 Nov

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Six-Year Incidence of Blindness and Visual Impairment in Kenya: The Nakuru Eye Disease Cohort Study.

Bastawrous Andrew A Mathenge Wanjiku W Wing Kevin K Rono Hillary H Gichangi Michael M Weiss Helen A HA Macleod David D Foster Allen A Burton Matthew J MJ Kuper Hannah H

Investigative ophthalmology & visual science 20161101 14

<h4>Purpose</h4>To describe the cumulative 6-year incidence of visual impairment (VI) and blindness in an adult Kenyan population. The Nakuru Posterior Segment Eye Disease Study is a population-based sample of 4414 participants aged ≥50 years, enrolled in 2007-2008. Of these, 2170 (50%) were reexamined in 2013-2014.<h4>Methods</h4>The World Health Organization (WHO) and US definitions were used to calculate presenting visual acuity classifications based on logMAR visual acuity tests at baseline ...[more]

PMID: 27820953

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Project description:ImportanceThe incidence of age-related macular degeneration (AMD) is unknown in Africa.ObjectiveTo estimate the 6-year cumulative incidence and progression of AMD in older adults (≥50 years old) in Nakuru, Kenya.Design, setting, and participantsThis 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 measuresIncident AMD in participants with no AMD at baseline and progression from early to late AMD.ResultsA 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 relevanceIn 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.

Project description:PurposeTo describe visual impairment (VI) over a 20-year period and its associations with age-related eye diseases and socioeconomic factors in the Beaver Dam Eye Study.DesignPopulation-based cohort study.ParticipantsFour thousand nine hundred twenty-six persons 43 to 86 years of age participated in the baseline examination phase from 1988 through 1990, and 3721, 2962, 2375, and 1913 persons participated in follow-up examinations each spaced 5 years apart from 1993 through 1995, 1998 through 2000, 2003 through 2005, and 2008 through 2010, respectively.MethodsBest-corrected visual acuity after refraction, assessed by the Early Treatment Diabetic Retinopathy Study protocol.Main outcome measuresIncidence of VI, defined as best-corrected visual acuity of poorer than 20/40 in the better eye in persons with one or both eyes 20/40 or better at the beginning of a 5-year interval, and incidence of severe VI, defined as best-corrected visual acuity of 20/200 or worse in the better eye in persons with one or both eyes better than 20/200 at the beginning of a 5-year interval.ResultsOverall incidence of VI between examinations (5-year interval) was 1.4% (varying from 0.1% in persons 50-54 years of age to 14.6% in those 85 years of age and older), whereas for severe VI it was 0.4% (varying from 0.0% in persons 50-54 years of age to 6.9% in those ? 85 years of age). The incidence of VI decreased for each (2003-2005 to 2008-2010; odds ratio fourth interval vs. first interval, 0.53; 95% confidence interval, 0.32-0.87; P = 0.01 period after adjustment for age, from the first 5-year interval between examinations (1988-1990 to 1993-1995) to the fourth and most recent 5-year interval ). This period effect was no longer significant after adjustment for age-related macular degeneration. Age-related macular degeneration remained the leading cause of incident severe VI (54% of eyes with incident severe VI, which was as low as 40% and as high as 57% for specific visits), with no evidence of a trend across visits. The overall frequency of VI correctable with new refraction was 38% of all eyes with VI.ConclusionsThese data provide population-based estimates that show a high (15%) 5-year incidence of VI in persons 85 years of age and older. Age-related macular degeneration remained the leading cause of severe VI in this population over the 20 years of the study.Financial disclosure(s)The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Project description:ObjectiveTo estimate the association between (1) visual impairment (VI) and (2) eye disease and 6-year mortality risk within a cohort of elderly Kenyan people.Design, setting and participantsThe baseline of the Nakuru Posterior Segment Eye Disease Study was formed from a population-based survey of 4318 participants aged ≥50 years, enrolled in 2007-2008. Ophthalmic and anthropometric examinations were undertaken on all participants at baseline, and a questionnaire was administered, including medical and ophthalmic history. Participants were retraced in 2013-2014 for a second examination. Vital status was recorded for all participants through information from community members. Cumulative incidence of mortality, and its relationship with baseline VI and types of eye disease was estimated. Inverse probability weighting was used to adjust for non-participation.Primary outcome measuresCumulative incidence of mortality in relation to VI level at baseline.ResultsOf the baseline sample, 2170 (50%) were re-examined at follow-up and 407 (10%) were known to have died (adjusted risk of 11.9% over 6 years). Compared to those with normal vision (visual acuity (VA) ≥6/12, risk=9.7%), the 6-year mortality risk was higher among people with VI (<6/18 to ≥6/60; risk=28.3%; risk ratio (RR) 1.75, 95% CI 1.28 to 2.40) or severe VI (SVI)/blindness (<6/60; risk=34.9%; RR 1.98, 95% CI 1.04 to 3.80). These associations remained after adjustment for non-communicable disease (NCD) risk factors (mortality: RR 1.56, 95% CI 1.14 to 2.15; SVI/blind: RR 1.46, 95% CI 0.80 to 2.68). Mortality risk was also associated with presence of diabetic retinopathy at baseline (RR 3.18, 95% CI 1.98 to 5.09), cataract (RR 1.26, 95% CI 0.95 to 1.66) and presence of both cataract and VI (RR 1.57, 95% CI 1.24 to 1.98). Mortality risk was higher among people with age-related macular degeneration at baseline (with or without VI), compared with those without (RR 1.42, 95% CI 0.91 to 2.22 and RR 1.34, 95% CI 0.99 to 1.81, respectively).ConclusionsVisual acuity was related to 6-year mortality risk in this cohort of elderly Kenyan people, potentially because both VI and mortality are related to ageing and risk factors for NCD.

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Project description:ImportanceVision loss is the third most common impairment worldwide. Although cost-effective interventions are available for preventing or curing most causes of vision loss, availability of these interventions varies considerably between countries and districts. Knowledge of the association between vision loss and socioeconomic factors is informative for public health planning.ObjectivesTo explore correlations of the prevalence of visual impairment with socioeconomic factors at country levels and to model and estimate a socioeconomic-adjusted disease burden based on these data.Design, setting, and participantsIn this cross-sectional study, the following data were collected from 190 countries and territories: the age-standardized prevalence of moderate to severe visual impairment (MSVI) and blindness from January 1 to December 31, 2010, across countries, human development index (HDI), gross domestic product (GDP) per capita, total health expenditure, total health expenditure as percentage of GDP (total health expenditure/GDP), public health expenditure as percentage of total health expenditure (public/total health expenditure), and out-of-pocket expenditure as percentage of total health expenditure (out-of-pocket/total health expenditure). Countries were divided into 4 levels (low, medium, high, and very high) by HDI. Data analysis was conducted from September 1, 2016, to July 1, 2017.Main outcomes and measuresThe correlations between prevalence data and socioeconomic indices were assessed.ResultsA strong negative association between prevalence rates of MSVI and blindness and socioeconomic level of development was observed. The mean (SD) age-standardized prevalence of MSVI decreased from 4.38% (1.32%) in low-HDI regions to 1.51% (1.00%) in very-high-HDI regions (P < .001). The national HDI level was attributable to 56.3% of global variation in prevalence rates of MSVI and 67.1% of global variation in prevalence rates of blindness. Higher prevalence rates were also associated with lower total health expenditure per capita, total health expenditure/GDP (β = −0.236 [95% CI, −0.315 to −0.157] for prevalence of MSVI; β = −0.071 [95% CI, −0.100 to −0.042] for prevalence of blindness), public/total health expenditure (β = −0.041 [95% CI, −0.052 to −0.031] for prevalence of MSVI; β = −0.014 [95% CI, −0.018 to −0.010] for prevalence of blindness), and higher percentage of out-of-pocket/total health expenditure (β = 0.044 [95% CI, 0.032-0.055] for prevalence of MSVI; β = 0.013 [95% CI, 0.009-0.017] for prevalence of blindness). Countries with increased burden of visual impairment and blindness can be easily identified by the results of the linear models. Socioeconomic factors could explain 69.4% of the global variations in prevalence of MSVI and 76.3% of the global variations in prevalence of blindness.Conclusions and relevanceBurden of visual impairment and socioeconomic indicators were closely associated and may help to identify countries requiring greater attention to these issues. The regression modeling described may provide an opportunity to estimate appropriate public health targets that are consistent with a country’s level of socioeconomic development.

Project description:ObjectiveThis study aims to estimate the incidence of severe binocular vision impairment and blindness (SVI/B) and to identify eye diseases and regional risk factors of persons with SVI/B at ages 50 years and older.MethodsWe designed an observational cohort study based on longitudinal, multifactorial, and administrative information of a random sample of 250,000 persons at ages 50+. All individuals were included in the process-produced health claims register of the Allgemeine Ortskrankenkasse in 2004, and were followed until 2015. We analyzed ten selected eye diseases and regional characteristics as risk factors for SVI/B using Cox models, adjusting for demographic characteristics and multi-morbidity.ResultsThe age-standardized incidence was 79 new diagnoses of SVI/B per 100,000 person-years (95%-CI: 76-82); 77 for males (72-82) and 81 for females (77-85). By adjusting for multiple factors, the model revealed and confirmed that individuals who were very old (Hazard ratio90+: 6.67; 3.59-12.71), male (1.18; 1.01-1.38), had multi-morbidities (three+ diseases: 3.36; 2.51-4.49), or had diabetes (1.26; 1.07-1.49) had an increased risk of SVI/B. Compared to persons without the particular eye disease (all p<0.001), persons diagnosed with secondary glaucoma had a multiple-adjusted 4.66 times (3.17-6.85) higher risk, those with retinal vascular occlusion had a 4.51 times (3.27-6.23) higher risk, and those with angle-closure glaucoma had a 4.22 times (2.60-6.85) higher risk. Population density was not a risk factor, while persons living in wealthier regions had 0.75 times (p=0.003) to 0.70 times (p<0.001) the risk of SVI/B than persons in the least wealthy regions of Germany.ConclusionThe study revealed and confirmed some profound risk factors of SVI/B at both the individual and the macro level. The sizes of the effects of the characteristics of the living context were smaller than those of the individual characteristics, especially for some severe eye diseases. While urbanity and access to health services had no effect, regional economic wealth was a risk factor for SVI/B. Future health care measures and advice by physicians should take these dimensions of inequalities in SVI/B into account.

Dataset Information

Six-Year Incidence of Blindness and Visual Impairment in Kenya: The Nakuru Eye Disease Cohort Study.

Purpose

Methods

Results

Conclusions

Publications

Six-Year Incidence of Blindness and Visual Impairment in Kenya: The Nakuru Eye Disease Cohort Study.

Similar Datasets

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