Lens opacities and mortality : the Barbados Eye Studies

Self-reported cataract surgery and 10-year all-cause and cause-specific mortality: findings from the National Health and Nutrition Examination Survey

PURPOSE

To investigate the association of self-reported cataract surgery with all-cause and cause-specific mortality using a large-scale population-based sample.

METHODS

Data from the 1999-2008 cycles of the National Health and Nutrition Examination Survey were used. A self-reported history of cataract surgery was considered a surrogate for the presence of clinically significant cataract surgery. Mortality data were ascertained from National Death Index records. Hazard ratios (HRs) and 95% confidence intervals (CIs) for survival were estimated using Cox proportional hazards regression models.

RESULTS

A total of 14 918 participants were included in the analysis. During a median follow-up of 10.8 (Interquartile range, IQR, 8.25-13.7) years, 3966 (19.1%) participants died. Participants with self-reported cataract surgery were more likely to die from all causes and specific causes (vascular disease, cancer, accident, Alzheimer's disease, respiratory disease, renal disease and others) compared with those without (all Ps <0.05). The association between self-reported cataract surgery and all-cause mortality remained significant after multiple adjustments (HR=1.13; 95% CI 1.01 to 1.26). For cause-specific mortality, multivariable Cox models showed that self-reported cataract surgery predicted a 36% higher risk of vascular-related mortality (HR=1.36; 95% CI 1.01 to 1.82). The association with other specific causes of mortality did not reach statistical significance after multiple adjustments.

CONCLUSIONS

This study found significant associations of self-reported cataract surgery with all-cause and vascular mortalities. Our findings provide potential insights into the pathogenic pathways underlying cataract.

Association between Age-related Cataract and Mortality in Sweden: A Long-term Population-based Follow-up Study

PURPOSE

To assess the relationship of age-related cataract with all-cause mortality in a Swedish population.

METHODS

Cox regression analyses were performed in a cohort of 746 residents 65-74 years of age, examined in a population survey in the rural district of Tierp, Sweden, 1984-86. To expand the sample size, 1,071 people were recruited by means of glaucoma case records established at the Eye Department in Tierp from 1978 to 2007. In this way, the cohort comprised 1,817 subjects, representing nearly 27,000 person-years at risk. The presence of cataract was determined based on retroillumination with lens opacities evident on slit-lamp examination. Information on deaths was obtained from the local population register.

RESULTS

By the conclusion of the study in April 2020, 1,633 deaths had been reported. Of these cases, 694 were affected by lens opacities or had history of cataract surgery at baseline. In multivariate analysis, including cataract, age, sex, smoking habits, cancer, diabetes, hypertension and ischemic heart disease, no association was found between cataract and mortality (hazard ratio 0.99; 95% confidence interval 0.90-1.10). Adjustment for participation in the population survey had no effect on the estimate.

CONCLUSION

In this long-term follow-up study of subjects 65-74-years-old in Sweden, cataract was not associated with all-cause mortality.

Age-related cataract and 10-year mortality: the Liwan Eye Study

PURPOSE

To explore the association between age-related cataract and 10-year mortality in an adult population in urban China.

METHODS

A total of 1405 participants aged 50 years or older were examined at baseline in the Guangzhou Liwan Eye Study. All participants were invited to attend a 10-year follow-up visit. Cataract cases were defined as either having visible lens opacity confirmed with direct ophthalmoscope under pupil dilation or previous history of cataract surgery. Visual impairment (VI) was defined as a visual acuity of 20/40 or worse in the better-seeing eye with habitual correction if worn. Body mass index (BMI) was based on anthropometric data. A brief questionnaire regarding family income, educational attainment and medical history of systemic disease was administered. Mortality rates were compared using the log-rank test and Cox proportional hazards regression models.

RESULTS

Among 1405 participants examined at baseline, 957 participants (68.1%) had visible lens opacity or history of cataract surgery. After 10 years, 320 (22.8%) participants died. The 10-year mortality rate was significantly higher in participants with cataract than in those without (30.1% versus 7.14%, log-rank p < 0.05). After adjusting for age, gender, family income, educational attainment, BMI, history of diabetes and hypertension and presence of VI, presence of cataract predicted a nearly threefold increase in the risk of mortality (HR, 2.99; 95% CI, 1.89-4.71).

CONCLUSIONS

Our findings that age-related cataract is a predictor for poorer survival compared to those without may imply that cataract is a biomarker of ageing and frailty.

Mortality during 6 years of follow-up in relation to visual impairment and eye disease: results from a population-based cohort study of people aged 50 years and above in Nakuru, Kenya

OBJECTIVE

To 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 PARTICIPANTS

The 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 MEASURES

Cumulative incidence of mortality in relation to VI level at baseline.

RESULTS

Of 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).

CONCLUSIONS

Visual 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.

Exceptional Human Longevity

Exceptional longevity represents an extreme phenotype. Current centenarians are survivors of a cohort who display delayed onset of age-related diseases and/or resistance to otherwise lethal illnesses occurring earlier in life. Characteristics of aging are heterogeneous, even among long-lived individuals. Associations between specific clinical or genetic biomarkers exist, but there is unlikely to be a single biomarker predictive of long life. Careful observations in the oldest old offer some empirical strategies that favor increased health span and life span, with implications for compression of disability, identification and implementation of lifestyle behaviors that promote independence, identification and measurement of more reliable markers associated with longevity, better guidance for appropriate health screenings, and promotion of anticipatory health discussions in the setting of more accurate prognostication. Comprehensive PubMed literature searches were performed, with an unbiased focus on mechanisms of longevity. Overall, the aggregate literature supports that the basis for exceptional longevity is multifactorial and involves disparate combinations of genes, environment, resiliency, and chance, all of which are influenced by culture and geography.

Glaucoma-associated long-term mortality in a rural cohort from India: the Andhra Pradesh Eye Disease Study

Aim

To evaluate glaucoma-associated mortality in a rural cohort in India.

Methods

The study cohort comprised individuals aged 40 years and above who took part in the Andhra Pradesh Eye Disease Study (APEDS1) during 1996–2000. All participants underwent detailed comprehensive eye examination. Glaucoma was defined using International Society of Geographic and Epidemiologic Ophthalmology criteria. This cohort was followed up after a decade (June 2009 to January 2010; APEDS2). Mortality HR analysis for ocular risk factors was performed using Cox proportional hazards regression after adjusting for sociodemographic, lifestyle and clinical variables.

Results

In APEDS1, 2790 individuals aged more than or equal to 40 years were examined. 47.4% were male. Forty-five participants had primary open angle glaucoma (POAG) and 66 had primary angle closure disease (PACD). Ten years later, 1879 (67.3%) were available, 739 (26.5%) had died and 172 (6.2%) had migrated; whereas 22 of the 45 (48.8%) with POAG and 22 of the 66 (33.3%) with PACD had died. In univariate analysis, a higher mortality was associated with POAG (HR 1.9; 95% CI 1.23 to 2.94), pseudoexfoliation (HR 2.79; 95% CI 2.0 to 3.89), myopia (HR 1.78; 95% CI 1.54 to 2.06) and unit increase in cup:disc ratio (HR 4.49; 95% CI 2.64 to 7.64). In multivariable analysis, only cup:disc ratio remained independently associated with mortality (HR 2.5; 95% CI 1.3 to 5.1). The association remained significant when other ocular parameters were included in the model (HR 2.1; 95% CI 1.03 to 4.2).

Conclusions

This is the first longitudinal study to assess the association of glaucoma and mortality in a rural longitudinal cohort in India. Increased cup:disc ratio could be a potential marker for ageing and would need further validation.

Association of Mortality with Ocular Diseases and Visual Impairment in the Age-Related Eye Disease Study 2: Age-Related Eye Disease Study 2 Report Number 13

PURPOSE

To evaluate the association of mortality with visual acuity (VA) impairment, age-related macular degeneration (AMD), and cataract surgery.

DESIGN

Cohort study.

PARTICIPANTS

Participants with at least intermediate AMD enrolled in a randomized controlled clinical trial of lutein/zeaxanthin and/or omega-3 fatty acids, the Age-Related Eye Disease Study 2 (AREDS2), for treatment of AMD and cataract.

METHODS

Baseline and annual eye examinations included best-corrected visual acuity (BCVA) assessments, slit-lamp examinations, and stereoscopic fundus photographs that were centrally graded for development of late AMD (central geographic atrophy or neovascular AMD) or pseudophakia. Cause-specific mortality was determined on the basis of the International Classification of Diseases 9th or 10th Revision codes. Risk of all-cause and cause-specific mortality was assessed with Cox proportional hazards models adjusted for age, sex, AMD severity, VA, history of cataract surgery, and assigned AREDS2 study treatment. Analyses included baseline covariates: race, education, smoking status, diabetes, and cardiovascular disease.

RESULTS

During follow-up (median 5 years), 368 (9%) of the 4203 AREDS2 participants died. Participants with neovascular AMD in 1 eye at baseline had a statistically significant increased risk for mortality compared with participants with no or few drusen (hazard ratio [HR], 1.56; 95% confidence interval [CI], 1.21-2.01; P < 0.001). Poorer survival was associated with bilateral cataract surgery before enrollment compared with baseline bilateral phakia (HR, 1.63; 95% CI, 1.29-2.07; P < 0.001) and with BCVA of less than 20/40 compared with participants with 20/40 or better (HR, 1.56; 95% CI, 1.06-2.30; P = 0.024), adjusted for age, sex, and statistically significant covariates. Participants who received antivascular endothelial growth factor therapies for neovascular AMD had decreased mortality compared with those who did not (HR, 0.71; 95% CI, 0.57-0.88; P = 0.002). The association between all-cause mortality and AREDS2 treatment whether assessing the main or individual treatment effect was not significantly different (omega-3 fatty acids main effect HR, 1.18; 95% CI, 0.96-1.45; P = 0.12; lutein/zeaxanthin main effect HR, 1.04; 95% CI, 0.85-1.28; P = 0.71).

CONCLUSIONS

In AREDS2, the presence of late AMD, bilateral cataract surgery, and VA less than 20/40 was associated with decreased survival. However, oral supplementation with omega-3 fatty acids, lutein plus zeaxanthin, zinc, or beta-carotene had no statistically significant impact on mortality.

Oxidative Stress Intensity in Lens and Aqueous Depending on Age-Related Cataract Type and Brunescense

Purpose

Cataract formation represents a serious problem in the elderly, and has a large impact on healthcare budget. The oxidative stress form and intensity might determine the cataract type and pigmentation, making efforts in the cataract prevention challenge more complex.

Methods

This is a retrospective cross-sectional review of 80 samples of aqueous humor and lens corticonuclear blocks. Aqueous samples were analyzed by the method of antioxidant activity estimation (%iMDA), while lipid peroxides (LP) and total sulfhydryl groups (TSH) were determined in lenses.

Results

Mixed and brunescent cataracts have statistically significant lower values of antioxidative %iMDA and TSH (p<0.001 for both parameters) and higher values of lipid peroxidation (p<0.001). No correlation between LP and TSH with maturity of cortical cataract was found, but there was a significant correlation with the %iMDA (p<0.05).

Conclusions

The role of the oxidative stress in cataractogenesis could not be the same for all cataract types. High level of lipid peroxides in pigmented cataracts may point to the different nature of pigment source than proteins solely, whereas lipid peroxidation and SH groups consumption in cortical cataractogenesis might be of less importance.

Whales, lifespan, phospholipids, and cataracts

This study addresses the question: why do rats get cataracts at 2 years, dogs at 8 years, and whales do not develop cataracts for 200 years? Whale lens lipid phase transitions were compared with the phase transitions of other species that were recalculated. The major phospholipids of the whale lens were sphingolipids, mostly dihydrosphingomyelins with an average molar cholesterol/phospholipid ratio of 10. There was a linear correlation between the percentage of lens sphingolipid and lens lipid hydrocarbon chain order until about 60% sphingolipid. The percentage of lens sphingolipid correlated with the lens lipid phase transition temperature. The lifespan of the bowhead whale was the longest of the species measured and the percentage of whale lens sphingolipid fit well in the correlation between the percentage of lens sphingolipid and lifespan for many species. In conclusion, bowhead whale lens membranes have a high sphingolipid content that confers resistance to oxidation, allowing these lenses to stay clear relatively longer than many other species. The strong correlation between sphingolipid and lifespan may form a basis for future studies, which are needed because correlations do not infer cause. One could hope that if human lenses could be made to have a lipid composition similar to whales, like the bowhead, humans would not develop age-related cataracts for over 100 years.

The impact of age-related cataract on measures of frailty in an aging global population

PURPOSE OF REVIEW

To review the associations among age-related cataract, frailty, and frailty outcomes (e.g., disabilities).

RECENT FINDINGS

It is predicted that the proportion of the population aged 65 and older, in developed and developing nations alike, will rise until at least 2050. The proportion of patients suffering from cataracts and frailty is expected to increase, as are age-related diseases. Although there are many papers reporting on the association between frailty outcomes, cataract, and visual impairment, there is a relative paucity of papers describing associations between frailty markers, cataract, and visual impairment.

SUMMARY

Reports regarding the relationship between frailty, visual impairment, cataract, and cataract surgery are limited, but gradually increasing. Further research is expected to clarify the mechanism of visual function or the impact of restored vision on frailty. Evidence for the effect of cataract on frailty and frailty outcomes after restoring vision by cataract surgery remains limited.

Age-related cataract, cataract surgery and subsequent mortality: a systematic review and meta-analysis

PURPOSE

Changes in lens may reflect the status of systemic health of human beings but the supporting evidences are not well summarized yet. We aimed to determine the relationship of age-related cataract, cataract surgery and long-term mortality by pooling the results of published population-based studies.

METHODS

We searched PubMed and Embase from their inception till March, 2014 for population-based studies reporting the associations of any subtypes of age-related cataract, cataract surgery with all-cause mortality. We pooled the effect estimates (hazards ratios [HRs]) under a random effects model.

RESULTS

Totally, we identified 10 unique population-based studies including 39,659 individuals at baseline reporting the associations of any subtypes of cataract with all-cause mortality from 6 countries. The presence of any cataract including cataract surgery was significantly associated with a higher risk of death (pooled HR: 1.43, 95% CI, 1.21, 2.02; P<0.001; I(2) = 64.2%). In the meta-analysis of 9 study findings, adults with nuclear cataract were at higher risks of mortality (pooled HR: 1.55, 95% CI, 1.17, 2.05; P = 0.002; I(2) = 89.2%). In the meta-analysis of 8 study findings, cortical cataract was associated with higher risks of mortality (pooled HR: 1.26, 95% CI, 1.12, 1.42; P<0.001, I(2) = 29.7%). In the meta-analysis of 6 study findings, PSC cataract was associated with higher risks of mortality (pooled HR: 1.37, 95% CI, 1.04, 1.80; P = 0.03; I(2) = 67.3%). The association between cataract surgery and mortality was marginally non-significant by pooling 8 study findings (pooled HR: 1.27, 95% CI, 0.97, 1.66; P = 0.08; I(2)= 76.6%).

CONCLUSIONS

All subtypes of age-related cataract were associated with an increased mortality with nuclear cataract having the strongest association among the 3 cataract subtypes. However, cataract surgery was not significantly related to mortality. These findings indicated that changes in lens may serve as markers for ageing and systemic health in general population.

Cataract, visual impairment and long-term mortality in a rural cohort in India: the Andhra Pradesh Eye Disease Study

BACKGROUND

A large-scale prevalence survey of blindness and visual impairment (The Andhra Pradesh Eye Diseases Study [APEDS1]) was conducted between 1996-2000 on 10,293 individuals of all ages in three rural and one urban clusters in Andhra Pradesh, Southern India. More than a decade later (June 2009-March 2010), APEDS1 participants in rural clusters were traced (termed APEDS2) to determine ocular risk factors for mortality in this longitudinal cohort.

METHODS AND FINDINGS

Mortality hazard ratio (HR) analysis was performed for those aged >30 years at APEDS1, using Cox proportional hazard regression models to identify associations between ocular exposures and risk of mortality. Blindness and visual impairment (VI) were defined using Indian definitions. 799/4,188 (19.1%) participants had died and 308 (7.3%) had migrated. Mortality was higher in males than females (p<0.001). In multivariable analysis, after adjusting for age, gender, diabetes, hypertension, body mass index, smoking and education status the mortality HR was 1.9 (95% CI: 1.5-2.5) for blindness; 1.4 (95% CI: 1.2-1.7) for VI; 1.8 (95% CI: 1.4-2.3) for pure nuclear cataract, 1.5 (95% CI: 1.1-2.1) for pure cortical cataract; 1.96 (95% CI: 1.6-2.4) for mixed cataract, 2.0 (95% CI: 1.4-2.9) for history of cataract surgery, and 1.58 (95% CI: 1.3-1.9) for any cataract. When all these factors were included in the model, the HRs were attenuated, being 1.5 (95% CI: 1.1-2.0) for blindness and 1.2 (95% CI: 0.9-1.5) for VI. For lens type, the HRs were as follows: pure nuclear cataract, 1.6 (95% CI: 1.3-2.1); pure cortical cataract, 1.5 (95% CI: 1.1-2.1); mixed cataract, 1.8 (95% CI: 1.4-2.2), and history of previous cataract surgery, 1.8 (95% CI: 1.3-2.6).

CONCLUSIONS

All types of cataract, history of cataract surgery and VI had an increased risk of mortality that further suggests that these could be potential markers of ageing.

The eye as a model of ageing in translational research--molecular, epigenetic and clinical aspects

The eye and visual system are valuable in many areas of translational research such as stem cell therapy, transplantation research and gene therapy. Changes in many ocular tissues can be measured directly, easily and objectively in vivo (e.g. lens transparency; retinal blood vessel calibre; corneal endothelial cell counts) and so the eye may also be a uniquely useful site as a model of ageing. This review details cellular, molecular and epigenetic mechanisms related to ageing within the eye, and describes ocular parameters that can be directly measured clinically and which might be of value in ageing research as the translational "window to the rest of the body". The eye is likely to provide a valuable model for validating biomarkers of ageing at molecular, epigenetic, cellular and clinical levels. A research agenda to definitively establish the relationship between biomarkers of ageing and ocular parameters is proposed.

Modeling the prevalence of age-related cataract: Waterloo eye study

PURPOSE

To report on the prevalence of age-related (AR) cataract in an optometric clinic population including male and female subgroups.

METHODS

Retrospective patient file data reviewed for the Waterloo Eye Study database included age, sex, date of lens extraction (LE), and presence of AR cataract [nuclear sclerosis (NS), cortical cataracts (CC), posterior subcapsular (PSC) or associated LE]. Prevalence (%) was calculated for overall AR cataract, NS, CC, PSC, and bilateral LE for all Waterloo Eye Study patients. Logistic regression analysis was used to create age functions for overall AR prevalence and for significant differences in cataract types for males and females. The distribution of homogeneous and mixed cataract and mean age of first LE were determined for males and females.

RESULTS

The prevalence of all AR, NS, CC, PSC, and bilateral LE was 35.3, 28.8, 9.9, 3.6, and 14.0%, respectively. Being female was associated with an increased prevalence of CC (odds ratio = 1.54, 95% confidence interval, 1.27 to 1.88) and bilateral LE (odds ratio = 1.41, 95% confidence interval, 1.09 to 1.84). Females reached 50% prevalence earlier than men for CC (76.7 vs. 82.6 years, p 0.05) and bilateral LE (84.6 vs. 90.5 years, p 0.05). Males had an earlier age of first LE than females (70.4 vs. 73.2 years; p 0.01).

CONCLUSIONS

Logistic regression modeling indicates that being female in this optometric clinic population was associated with an increased prevalence of CC, mixed cataract, surgical intervention, and later age of first LE. These data are important for public health planning.

Non-standard vision measures predict mortality in elders: the Smith-Kettlewell Institute (SKI) study

PURPOSE

To determine which vision tests predict mortality within 10 years in a community-based elderly sample.

METHODS

Nine hundred residents of Marin County, California 58 to 101 years of age (mean 75 years at baseline), underwent a battery of tests, including high contrast acuity, low contrast acuity, low contrast/low luminance acuity, acuity in glare, contrast sensitivity, color vision, stereopsis, standard and attentional fields. The association between the vision tests and mortality within 10 years of baseline was assessed with Cox Proportional Hazards models controlling for age, sex, education level, depression, cognitive status and self-reported medical conditions.

RESULTS

Forty-three percent of the sample died within 10 years of baseline. When controlling for mortality-related covariates, impairment in any of the vision measures was associated with increased risk of death. However, non-standard vision measures (ie, impairment in low contrast/low luminance acuity, standard field integrity and the impact of the attentional task on field integrity) were more highly associated with mortality than standard high contrast acuity.

CONCLUSIONS

In agreement with other studies, we find that visual impairment is a significant predictor of death. However, the strongest relationship was found for measures other than high contrast acuity. These results suggest that non-standard vision measures may be more sensitive indicators of generalized aging in the most elderly.

Lipids and the ocular lens

The unusually high levels of saturation and thus order contribute to the uniqueness of human lens membranes. In addition, and unlike in most biomembranes, most of the lens lipids are associated with proteins, thus reducing their mobility. The major phospholipid of the human lens is dihydrosphingomyelin. Found in significant quantities only in primate lenses, particularly human ones, this lipid is so extremely stable that it was reported to be the only lipid remaining in a frozen mammoth 40,000 years after its death. Unusually high levels of cholesterol add peculiarity to the composition of lens membranes. Beyond the lateral segregation of lipids into dynamic domains known as rafts, the high abundance of cholesterol in the human lens leads to the formation of patches of pure cholesterol. Changes in human lens lipid composition with age and disease as well as differences among species are greater than those observed for any other biomembrane. The relationships among lens membrane composition, structure, and lipid conformation reviewed in this article are unique to the mammalian lens and offer exciting insights into lens membrane function. This review focuses on findings reported over the last two decades that demonstrate the uniqueness of mammalian lens membranes regarding their morphology and composition. Because the membranes of human lenses do undergo the most dramatic changes with age and cataractogenesis, the final sections of this review address our current knowledge of the unusual composition and organization of adult human lens membranes with and without opacification. Finally, the questions that still remain to be answered are presented.

Dietary carbohydrate in relation to cortical and nuclear lens opacities in the melbourne visual impairment project

PURPOSE

In vitro and in vivo animal studies suggest that dietary carbohydrates play a role in cataractogenesis. Few epidemiologic studies have been conducted to evaluate this association. The objective of this study was to examine the cross-sectional associations between total carbohydrate intake, dietary glycemic index (dGI), and the risk of cortical and nuclear cataracts.

METHODS

After excluding 864 persons from 2473 eligible participants, 1609 eligible nondiabetic participants (mean age, 57.6 years, 55.9% female) in the Melbourne Visual Impairment Project (VIP) were enrolled. Dietary information derived from a semiquantitative food-frequency questionnaire and cataract status graded by the Wilmer protocol (cortical cataract: opacity >or=4/16; nuclear cataract grade >or=2) were collected. With the use of the generalized estimating approach to logistic regression to account for the lack of independence between the eyes of an individual, the associations between dietary carbohydrates and risk of cataract in eyes with no or a single type (pure) of cataract were examined.

RESULTS

Multivariate adjustment showed that pure cortical cataract (197 eyes) was significantly associated with total carbohydrate intake (odds ratio [OR] comparing the highest quartile with the lowest quartile = 3.19, 95% confidence interval [CI] = 1.10-9.27; P(trend) = 0.017). The OR for nuclear cataract (366 eyes) comparing the third quartile of dGI with the first quartile (OR = 1.64, 95% CI = 1.02-2.65) was significant, but there was not a consistent dose-response association (P(trend) = 0.75).

CONCLUSIONS

Carbohydrate intake may be optimized to prolong eye lens function. Because of the high proportion of subjects with missing covariates, these results warrant further study.

Influence of diabetes and cardiovascular disease on the long-term incidence of cataract: the Blue Mountains eye study

PURPOSE

To assess associations between diabetes and selected cardiovascular risk factors and long-term incident cataract and cataract surgery.

METHODS

A cohort of initially 3654 elderly Australians were followed over a period of 10 years. Questionnaires ascertained relevant history and fasting blood samples were taken. Impaired fasting glucose (IFG) and metabolic syndrome were defined using World Health Organization criteria. Discrete logistic models were used to assess risk of incident cataract.

RESULTS

After controlling for age, sex, and other factors, baseline diabetes predicted nuclear cataract (relative risk, RR, 1.64; 95% confidence interval (CI), 1.02-2.64) and IFG predicted cortical cataract (RR, 2.01; CI, 1.20-3.36). Each standard deviation (SD) increase in glucose was positively associated with cortical cataract (RR, 1.13; CI, 1.01-1.27). Higher body mass index (BMI) was positively associated with posterior subcapsular cataract (RR per SD, 1.20; CI, 1.03-1.41). Persons using anti-hypertensive medication had a higher incidence of cataract surgery (RR, 1.61; CI, 1.18-2.20). Metabolic syndrome was associated with an increased risk of all 3 cataract subtypes. Few other significant associations were found between cardiovascular disease, cardiovascular risk factors, and incident cataract or cataract surgery.

CONCLUSIONS

We confirmed diabetes as a risk factor for age-related cataract and IFG as a possible risk factor for cortical cataract. BMI and hypertension were also related to incident cataract. Overall, few associations were found between cardiovascular risk factors and long-term incident cataract. A cluster of metabolic abnormalities attributable to insulin resistance appears more likely to contribute to cataract formation than any individual cardiovascular risk factor alone.

Visual Acuity and Mortality in a Chinese Population

OBJECTIVE

To examine the relationship between visual acuity and mortality in a Chinese population.

DESIGN

Population-based cohort study.

PARTICIPANTS

Chinese persons in Singapore ages 40 to 79 years at baseline examination.

METHODS

The Tanjong Pagar Study in Singapore examined 1232 persons (response rate, 71.8%) at the baseline examination in 1997 and 1998. Participants had measurements of presenting and best-corrected visual acuity (VA) using standardized protocols. Mortality data were obtained from the National Death Registry, which linked subjects who had died since the baseline examination. Cause of death was determined from the International Classification of Diseases 9 codes. Analysis was performed on 1225 (99.4%) participants with VA data.

MAIN OUTCOME MEASURE

All-cause mortality.

RESULTS

By December 31, 2004 (median follow-up, 6.8 years), 126 persons had died. Participants with presenting VA in the better eye worse than 20/40 (logarithm of the minimum angle of resolution [logMAR] score, 0.3) had a significantly higher mortality rate (hazard ratio [HR], 2.9; 95% confidence interval [CI], 1.4-6.3, adjusting for age, gender, hypertension, diabetes, smoking, heart attack, stroke, and income) as compared with participants with VA of 20/20 (logMAR, 0.0). Associations were similar for best-corrected VA in the better eye (HR, 2.7; 95% CI, 1.4-5.5). Among clinic participants with logMAR VA measurements, each 1-line difference in presenting VA (logMAR gain, 0.10) was associated with a 4-fold increased risk of mortality (HR, 4.4; 95% CI, 1.9-10.2).

CONCLUSIONS

In this Chinese population in Singapore, visual impairment was associated independently with an increased risk of mortality.

Epidemiology of cataract: accomplishments over 25 years and future directions

The purpose of this review is to highlight the advances made by epidemiologic research into cataract. Considerable progress has been made in characterizing phenotypes, determining the prevalence and incidence in various population groups, and understanding risk factors for cataract. Cataract surgery research has documented functional improvements following surgery and has identified aspects of surgery delivery that could be made. Cataract is an independent marker of early mortality, providing a possible system for studying the aging process. Promising future work in cataract epidemiology is highlighted. Despite the availability of cataract surgery, cataract is still the leading cause of blindness worldwide. From a public health standpoint, research that can identify ways to delay onset or progression, or achieve the holy grail of prevention of cataract, should remain a leading priority.

Incident open-angle glaucoma and intraocular pressure

PURPOSE

To evaluate the role of baseline intraocular pressure (b-IOP) as a risk factor for incident open-angle glaucoma (OAG) in participants of African origin from the Barbados Eye Studies.

DESIGN

Population-based 9-year cohort study.

PARTICIPANTS

Three thousand two hundred twenty-two persons examined during the study period who were free of glaucoma at baseline and at risk of developing OAG during the 9-year follow-up.

METHODS

Study protocols were standardized and included ophthalmic and other measurements, automated perimetry, applanation tonometry, fundus photography, and comprehensive ophthalmologic examination for those referred. The product-limit approach was used to estimate incidence. Relationships between b-IOP and incidence were evaluated by adjusted relative risk ratios (RRs) with 95% confidence intervals (CIs), based on Cox regression models.

MAIN OUTCOME MEASURE

The 9-year incidence of OAG was based on both visual field and optic disc abnormalities, with ophthalmologic evaluations to exclude other possible causes.

RESULTS

The overall 9-year incidence of OAG was 4.4% (95% CI, 3.7%-5.2%), and the mean (standard deviation) b-IOP among persons at risk was 18.0 mmHg (4.1). Among the 125 incident OAG cases, the mean b-IOP was 21.9 mmHg and 46% had b-IOP of >21 mmHg. In contrast, the nonincident group had a mean b-IOP of 17.8 mmHg and only 12% had b-IOP of >21 mmHg. Overall, OAG risk increased by 12% with each 1-mmHg increase in IOP (RR, 1.12; 95% CI, 1.08-1.16). Incidence steadily increased from 1.8% (95% CI, 1.2%-2.7%) for persons with b-IOP of < or =17 mmHg (referent group) to 22.3% (95% CI, 15.8%-31.1%) for those with b-IOP > 25 mmHg, resulting in an adjusted RR of 13.1 (95% CI, 7.1-24.1) among the latter group. The attributable risk for IOP of >25 mmHg was 19%. Using 21 mmHg as a cutoff, the RR was 7.9 (95% CI, 3.8-16.2) and the attributable risk was 37%.

CONCLUSIONS

After 9 years' follow-up, the risk of OAG was positively related to IOP levels at baseline. Although persons with b-IOP of >25 mmHg had a 13-fold RR of developing OAG, most cases arose with lower b-IOP. This study thus confirms the role of IOP as an influential risk factor, yet at the same time underscores its limitations in predicting OAG.

Dietary carbohydrate intake and glycemic index in relation to cortical and nuclear lens opacities in the Age-Related Eye Disease Study

BACKGROUND

Little is known about the association between dietary carbohydrates and cataract in nondiabetic persons.

OBJECTIVE

The aim was to test whether recent dietary carbohydrate intakes or glycemic index (GI; a measure of carbohydrate intake quality) was associated with the presence of cortical or nuclear opacities.

DESIGN

A modified Block food-frequency questionnaire was used to obtain dietary information from 3377 participants (aged 60-80 y; 56% were women) in the Age-Related Eye Disease Study (AREDS). Lens status was evaluated by using the AREDS System for Classifying Cataracts. Associations were examined for eyes with only a single, or pure, type of lens opacity by using the generalized estimating approach to logistic regression to account for the lack of independence between the eyes of a person.

RESULTS

For participants in the highest quartile, dietary GI was associated with a higher prevalence of all pure nuclear opacities [grade >2; odds ratio (OR): 1.29; 95% CI: 1.04, 1.59; P for trend = 0.02] and moderate nuclear opacities (grade > or =4; OR: 1.43; 95% CI: 0.96, 2.14; P for trend = 0.052). The OR in a comparison of the highest with the lowest quartile of intake was 1.27 (95% CI: 0.99, 1.63; P for trend = 0.09) for cortical opacities of any severity (>0% of area opaque), and the OR increased somewhat for moderate cortical opacities (>5% of area opaque; OR: 1.71; 95% CI: 1.00, 2.95; P for trend = 0.056).

CONCLUSIONS

Results from the cross-sectional analysis of AREDS baseline data suggest that dietary glycemic quality and dietary carbohydrate quantity may be associated with prevalent nuclear and cortical opacities, respectively.

Frailty, morbidity and survival

Frailty, as a reflection of decreased physical reserve rather than disability, is assessed by various functional tests rather than by specific disease burden. We investigated association of measures of frailty to disease outcomes and survival in a population-based study of Midwestern adults. The markers of frailty we evaluated were: time to walk a measured course (gait-time), handgrip strength, peak respiratory flow rate, ability to stand from a sitting position without using arms, and best corrected visual acuity. A history of cardiovascular disease, cancer, and hypertension were obtained. Data were collected at the third examination (1998--2000) of the Beaver Dam Eye Study cohort (n=2962). Follow-up for mortality occurred up to 412 years after the 1998--2000 examinations. Markers of frailty were significantly associated with age. Values in the highest quartile (slowest) of gait-time, lowest quartile of peak expiratory flow rate, lowest quartile of handgrip strength, inability to stand from sitting in one try (those not in a wheelchair), and visual impairment were combined in an index to denote a general description of frailty. The range of the index was 0 (no frailty) to 5 (maximum frailty). Greater frailty was significantly associated with cardiovascular disease and hypertension. Frailty was associated with poorer survival over an interval of 412 years after adjusting for age, sex, hypertension, diabetes, and cardiovascular disease. Greater frailty was associated with greater likelihood of concurrent medical conditions and with decreased survival.

Age-related maculopathy: A risk indicator for poorer survival in women

PURPOSE

To examine patient survival in age-related maculopathy in a 14-year follow-up study.

DESIGN

Population-based 14-year cohort study.

PARTICIPANTS

Nine hundred forty-six residents, aged 60 to 80 years, living in the Osterbro district of Copenhagen, Denmark, participated in the first examination conducted from 1986 to 1988. These participants were followed until death or until May 1, 2002, whichever came first.

METHODS

Participants underwent an extensive ophthalmologic examination at Rigshospitalet, the National University Hospital of Copenhagen. Standardized protocols for physical examination, blood samples, and data from the National Central Person Register, the National Death Register, and the National Patient Register were used.

MAIN OUTCOME MEASURES

Mortality and age-related maculopathy.

RESULTS

By May 1, 2002, 60.9% (577 of 946) of the participants of the baseline study cohort had died. The adjusted 14-year cumulative mortality hazard ratio for subjects with early and late age-related maculopathy at baseline was 1.26 (95% confidence interval [CI], 1.06-1.51). We identified a strong correlation between mortality and age-related maculopathy among women (relative risk, 1.59; 95% CI, 1.23-2.07) but not among men.

CONCLUSIONS

When adjusting for survival-related factors, age-related maculopathy is a significant risk indicator for poorer survival in women and may be a marker of underlying serious systemic factors or aging processes specific to women.

Lens lipids and maximum lifespan

Unlike in most organs, the lipid composition of lenses varies dramatically among species and with age. The focus of this study is to assess how these changes relate to lifespan. Studies on cataract suggest that the lens may serve as a window into the processes leading to accelerated mortality. As a first step toward elucidating cellular processes in the lens that may serve as markers for accelerated mortality, we examined the correlation between species-dependent and age-related lens lipid compositional differences and maximum life span. We included data from camels, which, even in old age, rarely develop cataracts although they live under adverse conditions. Camel lens lipids were mainly composed of sphingolipids (77%) and phosphatidylcholines (23%). Bovine lens lipid composition was comparable to a previous study, and both bovine lens sphingolipids, phosphatidylcholines and camel lens phosphatidylcholines content fit well (within the 95% confidence limits) in the curve obtained by plotting maximum life spans of other species with sphingolipids and phosphatidylcholines. Lifespan was directly related to lens sphingolipid content and indirectly related to lens phosphatidylcholine content. The camel lens sphingolipid value was significantly above the curve for other species. Except for the camel lens nucleus, lipid order and sphingolipid content were linearly related, p < 0.005 with a slope of 0.85+/-0.07, and intercept of 6.9+/-3.8. Lipid phase transition temperature and sphingolipid content were also linearly related, p = 0.01 with a slope of 0.20+/-0.07, and intercept of 21.7+/-5.3. Our data support the hypothesis that humans have adapted so that their lens membranes have a high sphingolipid content that confers resistance to oxidation, allowing these membranes to stay clear for a relatively longer time than is the case in many other species. Age-related changes in human lens lipid composition may serve as a marker for oxidative stress and may reflect systemic oxidative insult, providing a window into the health of an individual.

Overall adherence to the dietary guidelines for americans is associated with reduced prevalence of early age-related nuclear lens opacities in women

Few studies have examined the efficacy of the Dietary Guidelines for Americans in the prevention of age-related chronic disease, such as age-related cataract. We examined whether adherence to the Guidelines was associated with a lower prevalence of age-related nuclear lens opacities in women. Eye exams were conducted in 479 Nurses' Health Study participants aged 52 to 73 y without previously diagnosed cataract or diabetes living in the Boston, MA area. Four FFQs, collected during a 9- to 11-y period before evaluation of lens status, were used to define diet quality according to the following: 1) daily number of servings of fruits, vegetables, and whole grains; 2) Recommended Foods Score (RFS); and 3) Healthy Eating Index (HEI). Nuclear opacities were defined as scores >/= 2.5 using the Lens Opacification Classification System III. After adjusting for age, smoking, and other risk factors, women in the highest quartile category of HEI scores were significantly less likely to have nuclear opacities than those in the lowest category [odds ratio (OR) = 0.47; 95% CI: 0.26-0.84]. This association appeared to be stronger among nonusers of supplemental vitamin C (OR = 0.23; 95% CI: 0.10-0.52). Decreased prevalence odds of nuclear opacities were also observed with high intake of fruit (OR = 0.58; 95% CI: 0.32-1.05) and whole grains (OR = 0.64; 95% CI: 0.36-1.15). These results suggest that overall compliance with the Dietary Guidelines, as measured by the HEI, protects against nuclear opacities.

Associations of mortality with ocular disorders and an intervention of high-dose antioxidants and zinc in the Age-Related Eye Disease Study: AREDS Report No. 13

OBJECTIVE

To assess the association of ocular disorders and high doses of antioxidants or zinc with mortality in the Age-Related Eye Disease Study (AREDS).

METHODS

Baseline fundus and lens photographs were used to grade the macular and lens status of AREDS participants. Participants were randomly assigned to receive oral supplements of high-dose antioxidants, zinc, antioxidants plus zinc, or placebo. Risk of all-cause and cause-specific mortality was assessed using adjusted Cox proportional hazards models.

RESULTS

During median follow-up of 6.5 years, 534 (11%) of 4753 AREDS participants died. In fully adjusted models, participants with advanced age-related macular degeneration (AMD) compared with participants with few, if any, drusen had increased mortality (relative risk [RR], 1.41; 95% confidence interval [CI], 1.08-1.86). Advanced AMD was associated with cardiovascular deaths. Compared with participants having good acuity in both eyes, those with visual acuity worse than 20/40 in 1 eye had increased mortality (RR, 1.36; 95% CI, 1.12-1.65). Nuclear opacity (RR, 1.40; 95% CI, 1.12-1.75) and cataract surgery (RR, 1.55; 95% CI, 1.18-2.05) were associated with increased all-cause mortality and with cancer deaths. Participants randomly assigned to receive zinc had lower mortality than those not taking zinc (RR, 0.73; 95% CI, 0.61-0.89).

CONCLUSIONS

The decreased survival of AREDS participants with AMD and cataract suggests that these conditions may reflect systemic rather than only local processes. The improved survival in individuals randomly assigned to receive zinc requires further study.

The environment and the eye

The use of the 'environment' has become extended to include population changes, the 'domestic' environment, and cultural factors, in addition to physical influences such as global warming and ultraviolet radiation (UVR). The likely effects of each of these classes of agents on the eye and rates of blindness are illustrated by reference mainly to cataract and trachoma--two of the commonest causes of the world blindness.Trachoma infection and its blinding consequences could be eventually eliminated by environmental measures and changes in behaviour. While the threat of increased incidence of blindness from cataract due to ozone depletion and greater solar UVR has receded, global warming may become a factor in the early onset and rapid progression of cataract. Although we continue to need research into the physical and biological causes of cataract, elimination of world blindness will only be achieved when we understand the conceptual and cultural environments which are inhibiting the acceptance of cataract surgery.

Association between lens opacities and mortality in the Priverno Eye Study

BACKGROUND

Lens opacities are associated with a higher risk of death, although there are some discrepancies regarding the specific types of cataract representing risk. The purpose of the present study was to further investigate the relationships between different types of lens opacity and patient survival.

METHODS

In 1987, 860 residents of Priverno, Italy, aged 45-69 years underwent an ophthalmologic examination. Based on patient histories and the findings of the slit-lamp examination, each of the 860 patients was classified according to the type of opacity (pure cortical, pure nuclear, pure posterior subcapsular, mixed, and surgical aphakia). The survivors of the original cohort were re-examined in 1994. Death and survival rates were computed by the Kaplan-Meier method. Associations between mortality and significant factors were included in a stepwise Cox proportional-hazards regression model.

RESULTS

Forty-four members of the original cohort had died during the 7-year follow-up. Age-adjusted survival curves based on Kaplan-Meier estimates showed significantly lower survival in those whose baseline examinations had revealed pure nuclear opacity (log rank test: P=0.020) and aphakia (log rank test: P<0.001). When adjusted for other mortality risk factors (age, sex, diabetes, cardiovascular diseases), the hazard ratio was 4.32 for pure nuclear opacity (95% CI 1.13-16.4) and 18.3 for aphakia (95% CI 3.21-104.0).

CONCLUSIONS

The analysis of the Priverno data seems to confirm an association between lower survival and cataracts, particularly those confined to the lens nucleus and those that had already prompted surgery.

Cardiovascular disease, vascular risk factors and the incidence of cataract and cataract surgery: the Blue Mountains Eye Study

PURPOSE

To assess whether an association exists between cardiovascular disease, vascular risk factors and incident cataract and cataract surgery.

METHODS

The Blue Mountains Eye Study examined 3654 participants > or = 49 years of age during 1992-4, then 2335 survivors (75.1%) after five years. Trained interviewers administered a vascular history questionnaire; height, weight and blood pressure were measured. Lens photographs from both examinations were graded for presence of cortical, nuclear or posterior subcapsular cataract.

RESULTS

Obesity (body mass index > or = 30 kg/m2) was significantly associated with increased incidence of both cortical [odds ratio (OR) 1.6, 95% confidence interval (CI) 1.2-2.2] and posterior subcapsular cataract (OR 2.1, CI 1.2-3.7). Hypertensive participants using medication and aged less than 65 years at baseline had a higher incidence of posterior subcapsular cataract (OR 3.4, 95% CI 1.3-8.4) than normotensive subjects. A history of angina was associated with higher cataract surgery incidence (OR 2.1, 95% CI 1.3-3-5).

CONCLUSIONS

These longitudinal data provide some evidence supporting a relationship between cardiovascular disease, vascular risk factors and incident cataract and cataract surgery. The findings confirm a number of associations previously documented in cross-sectional data.

The association between cataract and mortality among older adults

CONTEXT

Previous research has suggested that persons with cataract have an increased risk of death.

OBJECTIVE

To compare the mortality experience of patients with cataract who elect surgery, patients with cataract who do not elect surgery, and patients without cataract independent of potentially confounding risk factors.

DESIGN

Cohort study.

SETTING

Ophthalmology and optometry clinics affiliated with the Callahan Eye Foundation Hospital in Birmingham, Alabama.

PATIENTS

384 persons with and without cataract.

MAIN OUTCOME MEASURE

Mortality.

RESULTS

Of the 384 study subjects, 286 had cataract, of whom 200 elected to have cataract surgery. Patients with cataract who did and did not elect surgery had significantly higher mortality compared to those without cataract (crude mortality rate ratio (MRR) 3.9 (95% confidence interval (CI) 1.5-9.8) and 7.3 (95% CI 2.8-19.1), respectively). After adjustment for age, gender, race, education, chronic medical conditions, smoking, drinking, depression, and cognitive status, the no-surgery cataract group had an elevated mortality rate (MRR 3.2 (95% 1.2-9.0)), compared to the no-cataract group, with a borderline elevation in MR for the surgery group (MRR 2.0 (95% 0.8-5.9). Limiting the study population to non-diabetics or those without concurrent eye conditions (glaucoma, maculopathy, retinopathy) did not materially influence the adjusted MRRs although the precision of the estimates was reduced.

CONCLUSIONS

The results suggest that older persons with cataract, in particular those who decline surgery, have an increased risk of death, supporting the hypothesis that age-related cataract reflects systemic as well as localized ocular disease.

Five year incidence of cataract surgery: the Blue Mountains Eye Study

AIMS

To assess the 5 year incidence of cataract surgery in an older population based prospective cohort.

METHODS

5 Year prospective follow up of the population based Blue Mountains Eye Study (BMES) performed in 1992. The follow up study examined 2335 survivors (75.1%) of the 3654 baseline participants. Baseline and 5 year slit lamp and retroillumination lens photographs were graded for presence of cortical, nuclear, or posterior subcapsular cataract using the Wisconsin cataract grading method and cataract surgery was documented from the history and the clinical examination.

RESULTS

An overall cataract surgery rate of 5.7% in first or both eyes was documented. The incidence was 0.3% in people aged 49-54 years at baseline, 1.7% for ages 55-64 years, 7.9% for ages 65 to 74 years, and 17.4% in people aged 75 years or older. The rate of surgery in first or both eyes was 6.0% in women and 5.2% in men, age adjusted p = 0.66. Bilateral cataract surgery was performed during follow up on 2.7% of participants, while 43.1% of unilateral phakic cases had second eye surgery. Presence of any posterior subcapsular (PSC) cataract, either alone or in combination with other cataract types, was the most likely type of cataract at baseline to be associated with incident cataract surgery. Baseline age was the most important non-ocular variable predicting incident cataract surgery.

CONCLUSIONS

This study has documented age specific rates for 5 year incident cataract surgery in an older community. The finding of relatively similar incidence rates and ocular predictors of cataract surgery to those reported by the Beaver Dam Eye Study, Wisconsin, United States, is of interest, given previous documented similarities between these two populations.