Case-control studies and risk factors for cataract in two population studies in Nigeria

Risk of cataract in smokers: A meta-analysis of observational studies

OBJECTIVE

The aim of the study was to compare the risk of cataract in smokers and ex-smokers.

METHODS

A systematic search of observational studies was carried out in Medline, Embase, and Lilacs databases. Studies that have evaluated the association between cigarette smoking and any type of clinically diagnosed cataract were selected. The association estimators were extracted, adjusted at least by age, and were combined using random-effects models, by subtype of study (cohort, case control and cross sectional), subtype of cataract (nuclear, cortical, and posterior subcapsular), and exposure (current smoker or ex-smoker). Statistical heterogeneity, meta-regression analysis and publication bias were assessed.

RESULTS

A total of 13 cohort studies, 12 case-control studies, and 18 cross-sectional studies were selected. A risk of cataract was found in current smokers: cohort (OR: 1.41; 95%CI: 1.24-1.60), cases and controls (OR: 1.45; 95%CI: 1.08-1.96), and cross-sectional studies (OR: 1.21; 95%CI: 1.09-1.34); risk of nuclear cataract: cohort (OR: 1.71; 95%CI: 1.47-1.98), case-control (OR: 1.79; 95%CI: 1.43-2.25), and cross sectional studies (OR: 1.45; 95%CI: 1.27-1.65). There was no risk of cortical or posterior subcapsular cataract in ex-smokers.

CONCLUSIONS

There is a risk of cataract in smokers, particularly nuclear type. With cross-sectional studies, similar results are obtained with cohorts and cases and controls.

Cataract frequency and subtypes involved in workers assessed for their solar radiation exposure: a systematic review

Cataract is currently the primary cause of blindness worldwide, and one of its main risk factors is solar ultraviolet radiation exposure. According to the localization of lens opacities, three main subtypes of cataract are recognized: nuclear, cortical and posterior subcapsular cataract. One of the main determinants of individual long-term solar radiation exposure is outdoor work. We systematically reviewed scientific literature from the last 20 years to update the recent development of research on the risk of cataract in outdoor workers and on the specific subtypes involved, also investigating the methods applied to evaluate the occupational risk. A total of 15 studies were included in the review, of which 12 showed a positive association. The studies confirm the relationship of long-term occupational solar radiation exposure with cortical cataract and give new support for nuclear cataract, although no substantial new data were available to support a relation with the posterior subcapsular subtype. In most of the studies, the exposure assessment was not adequate to support a representative evaluation of the ocular risk; however, outdoor work is clearly a relevant risk factor for cataract. Further research providing a better evaluation of the relation between solar radiation exposure levels and lens damage in workers is needed and aimed to establish adequate occupational exposure limits and better preventive measures, studying also their effectiveness.

Solar Radiation Exposure and Outdoor Work: An Underestimated Occupational Risk

A considerably high number of outdoor workers worldwide are constantly exposed for the majority of their working life to solar radiation (SR); this exposure is known to induce various adverse health effects, mainly related to its ultraviolet (UV) component. The skin and the eye are the principal target organs for both acute and long-term exposure. Actinic keratosis, non-melanoma skin cancers, and malignant melanoma are the main long-term adverse skin effects, whereas in the eye pterygium, cataracts, and according to an increasing body of evidence, macular degeneration may be induced. Despite this, SR exposure risk is currently undervalued, if not neglected, as an occupational risk factor for outdoor workers. SR exposure is influenced by various environmental and individual factors, and occupation is one of the most relevant. For a better understanding of this risk and for the development of more effective prevention strategies, one of the main problems is the lack of available and adequate methods to estimate SR worker exposure, especially long-term exposure. The main aims of this review were to provide a comprehensive overview of SR exposure risk of outdoor workers, including the UV exposure levels and the main methods recently proposed for short-term and cumulative exposure, and to provide an update of knowledge on the main adverse eye and skin effects. Finally, we also outline here preventive interventions to reduce occupational risk.

Vision health disparities in blindness and visual impairment in Nigeria: A review of the Nigerian National Blindness and Visual Impairment Survey

Purpose: Blindness and visual impairment have become public health problems with prevalence increasing year after year. Nigeria, the most populated country in Africa, is also very diverse in terms of geographical location, ethnicity and culture. This study looks at and considers the vision health disparities in blindness and visual impairment in Nigeria using socio-demographic factors such as gender, geopolitical zones, place of residence and literacy.Methods: A comprehensive literature search was conducted on PubMed and Google Scholar databases from May 2014 to May 2015. The search included articles from 2001 to May 2015 as well as a review of the Nigerian National Blindness and Visual Impairment Survey.Results: The male dominance culture and lower literacy levels among women in Nigeria have led to a higher prevalence of blindness and visual impairment among women compared to men. In Nigeria, eye diseases that lead to blindness and visual impairment occur more in certain geopolitical zones and ecological regions than others. More Nigerians live in remote rural areas, with little or no access to health care, rather than in urban areas where there are more eye care practitioners and better facilities for care.Conclusion: Differences in gender, geopolitical zones, place of residence and literacy are responsible for existing vision health disparities in blindness and visual impairment in Nigeria.

Different amounts of alcohol consumption and cataract: a meta-analysis

PURPOSE

To evaluate the association between different amounts of alcohol consumption and the risk of age-related cataract.

METHODS

We searched PubMed and Embase from their inception until May 2014 for case-control or cohort studies with data on alcohol consumption and age-related cataract. Heavy alcohol consumption was defined as more than two standard drinks per day, which is equal to a daily intake of 20 g of alcohol or 140 g per week. Moderate consumption was defined as less than 20 g of alcohol per day but more than never any. We performed separate meta-analyses for the associations of moderate or heavy alcohol consumption with age-related cataract under a random-effects model, respectively.

RESULTS

Five case-control and five cohort studies were identified through comprehensive literature search. In the meta-analysis of 10 studies, the associations between moderate alcohol consumption and age-related cataract were marginally nonsignificant (pooled relative risk, 0.88; 95% confidence interval, 0.74 to 1.05; I = 82.1%), whereas heavy alcohol consumption was associated with an increased risk of age-related cataract (pooled relative risk, 1.26; 95% confidence interval, 1.06 to 1.50; I = 58.9%). The association between heavy alcohol consumption and cataract was stronger in case-control than in cohort studies. Adjusting for smoking as a potential confounder attenuated the association between heavy alcohol consumption and cataract.

CONCLUSIONS

Heavy alcohol consumption significantly increased the risk of age-related cataract, whereas moderate consumption may be protective for this ocular condition. Clinically, information on a patient's alcohol drinking history might be valuable to general physicians and ophthalmologists when there is a diagnosis of age-related cataract and should be collected on a routine basis in eye clinics.

Iris color and associated pathological ocular complications: a review of epidemiologic studies

AIM

To elucidate the associations of iris color with major eye diseases.

METHODS

A systematic search on Medline with coverage up to August 2013 was conducted. Assessment of the quality of studies based on their levels of evidence was in accordance with the Centre for Evidence-Based Medicine, Oxford, United Kingdom.

RESULTS

A relationship between darker iris color and an increased risk of age-related cataract has been reported from cross-sectional studies and prospective cohort studies. There was no consistent evidence supporting a major role of iris color in the development or progression of age-related macular degeneration. The association of iris color with ocular uveal melanoma has been confirmed by a meta-analysis of observational studies previously. The etiologic synergism between light iris color and environmental exposure such as UV the exposure of UV radiation was found. There were no studies evaluating the refractive associations with iris color but there may be a possible link between iris color and myopia.

CONCLUSION

Darker iris color is associated with an increased risk of cataract and a reduced risk of ocular uveal melanoma. The association of iris color with age-related macular degeneration is not confirmed. Ophthalmologists should be aware that the risk of ocular disorders appears to vary by differences in iris color.

Alcohol intake and the risk of age-related cataracts: a meta-analysis of prospective cohort studies

Purpose

Epidemiologic studies assessing the relationship between alcohol consumption and the risk of age-related cataracts (ARCs) led to inconsistent results. This meta-analysis was performed to fill this gap.

Methods

Eligible studies were identified via computer searches and reviewing the reference lists of these obtained articles. Pooled estimates of the relative risks (RR) and the corresponding 95% confidence Intervals (CI) were calculated using random effects models.

Results

Seven prospective cohort studies involving a total of 119,706 participants were ultimately included in this meta-analysis. Pooled results showed that there is no substantial overall increased risk of ARC due to heavy alcohol consumption. The estimated RRs comparing heavy drinkers versus non-drinkers were 1.25 (95% CI: 1.00, 1.56) for cataract sugery, 1.06 (95% CI: 0.63, 1.81) for cortical cataracts, 1.26 (95% CI: 0.93, 1.73) for nuclear cataracts, and 0.91 (95% CI: 0.32, 2.61) for posterior subcapsular cataracts (PSCs), respectively. No significant associations between moderate alcohol consumption and cataracts were observed. The pooled RRs comparing moderate drinkers versus non-drinkers were 0.90 (95% CI: 0.64, 1.26) for cataract surgery, 0.97 (95% CI: 0.75, 1.25) for cortical cataracts, 0.91 (95% CI: 0.76, 1.08) for nuclear cataracts, and 0.97 (95% CI: 0.49, 1.91) for PSCs, respectively.

Conclusions

This meta-analysis suggests that there is no substantial overall increased risk of ARC due to alcohol intake. Because of the limited number of studies, the findings from our study must be confirmed in future research via well-designed cohort or intervention studies.

Association between cataract and the degree of obesity

PURPOSE

To investigate the association between the degree of obesity and cataract.

METHODS

We examined 3248 subjects (1421 men and 1827 women) aged 50 years and older who did not have a previous cataract operation. Data were derived from the fourth Korea National Health and Nutrition Examination Survey (2009). Cataract was evaluated by using Lens Opacities Classification System III. Body mass index was categorized into four groups (underweight, <18.5 kg/m(2); normal weight, 18.5 to 22.9 kg/m(2); overweight, 23.0 to 24.9 kg/m(2); and obese, ≥25.0 kg/m(2)). Association between the degree of obesity and cataract was evaluated using logistic regression analyses with adjustments of age, the total pack-years of cigarettes smoked, the amount of pure alcohol (g) consumed per day, daily time spent in vigorous physical activity, diabetes mellitus, sunlight exposure, education level, and income.

RESULTS

Compared with the normal-weight group, the overweight group had significantly lower risk of any type of cataract (odds ratio, 0.70; 95% confidence interval, 0.50 to 0.97) in men and (odds ratio, 0.70; 95% confidence interval, 0.51 to 0.97) in women in the multiple logistic regression analyses. We could not find any unusual lifestyles or metabolic risks for explaining this low cataract prevalence in the overweight groups. However, nutrient intakes (e.g., vitamin B2, niacin, vitamin C, and vitamin A) were highest in the overweight group.

CONCLUSIONS

The overweight group had significantly lower risk of cataract formation than the normal-weight group in Korean population.