|Year : 1996 | Volume
| Issue : 4 | Page : 213-217
A case control study of senile cataract in a hospital based population
Sengamedu Srinivasa Badrinath1, Tarun Sharma1, Jyotirmoy Biswas1, V Srinivas2
1 Sankara Nethralaya Vision Research Foundation, Madras, India
2 Indian Council of Medical Research (New Delhi), India
Vision Research Foundation, 18 College Road, Madras 600 006
Source of Support: None, Conflict of Interest: None
A case-control study (244 cases and 264 controls) was done during 1986-89 on a hospital based population to evaluate the risk factors associated with the etiology of senile cataract. Patentis with age between 40-60 years, visual acuity of 6/9 or less, and presence of lenticular opacity of senile origin were included as cases. Age matched individuals with absence of lenticular opacity made up the controls. Multivariate logistic regression analysis revealed that higher systolic BP and number of meals were significantly (P < 0.05) associated with presence of senile cataract; whereas higher weight, education and income, and utilization of cooking water had a significant protective effect against senile cataract. The present study helps the clinician to understand the possible risk factors associated with the development of senile cataract and could be helpful in designing a intervention strategy in future.
Keywords: Case-control study, senile cataract.
|How to cite this article:|
Badrinath SS, Sharma T, Biswas J, Srinivas V. A case control study of senile cataract in a hospital based population. Indian J Ophthalmol 1996;44:213-7
|How to cite this URL:|
Badrinath SS, Sharma T, Biswas J, Srinivas V. A case control study of senile cataract in a hospital based population. Indian J Ophthalmol [serial online] 1996 [cited 2019 Dec 6];44:213-7. Available from: http://www.ijo.in/text.asp?1996/44/4/213/24563
Senile cataract is an important cause of preventable blindness, affecting 12 to 15 million persons worldwide. In India, approximately 3.8 million persons become blind from cataract each year. Moreover, in India, senile cataract develops at a relatively younger age compared to developed countries., It has been estimated that if the development of cataract could be delayed by 10 years, the number of cataract operations would decrease by 45%. Previous epidemiological studies have enumerated lower education, decreased cloud cover, use of aspirin, diets low in selected nutrients, higher blood pressure, lower body mass index, use of cheaper cooking fuels, lower levels of an antioxidant index, cigarette smoking, increased UV - B radiation and diabetes as risk factors associated with senile cataract.
The present case control study was designed to determine the sociodemographic, environmental, genetic, nutritional and systemic factors that might be associated with the development of senile cataract in a hospital based population.
| Materials and methods|| |
The study was performed in a hospital-based population from 1986 through 1989. All participants were between 40 and 60 years of age and were residents of the city of Madras for past 5 years at least. Patients were considered as "cases" if the lenticular opacity accounted for visual acuity of 6/9 or less in the involved eye. Patients with eye diagnosis other than cataract or without any ocular problem resulting in decreased vision formed the "control" group. A written informed consent was obtained from each patient for inclusion into the study. Patients with following criteria were excluded.
- 1. Age below 40 or above 60 years.
- 2. Congenital, developmental, traumatic or complicated cataract.
- 3. Any other ocular disease like corneal opacity, uveitis, glaucoma or macular degeneration that can independently cause diminution of vision.
- 4. History of receiving topical or systemic steroids within 2 years or for a continuous period of 6 or more weeks.
- 5. Blood pressure > 160/96 mm Hg.
- 6. Random blood sugar > 160 mg/dl.
- 7. Non resident of Madras.
A total of 244 cases (123 males; 121 females) and 264 controls (151 males; 113 females) were studied. The age distribution showed that the "cases", on average were 4.7 years older than the "controls". All patients had their best corrected visual acuity assessed, lenses evaluated with the slit-lamp biomicroscope, intraocular pressure recorded, and fundi examined after pupillary dilatation. Physiological variables studied were height, weight, systolic and diastolic blood pressures, random blood sugar and pulse rate. A sociodemographic and environmental questionnaire was addressed to religion, educational status, marital status, exposure to sunlight, consanguinity, family history of cataract, economic status, smoking, alcohol intake and type of cooking fuel used. The information on monthly income was collected as Rs. less than Rs. 300, Rs. 301 to 750 and more than Rs. 750 and were coded as 1, 2 and 3 respectively. Any history of systemic illness and treatment taken was elicited and a retrospective dietary assessment was made for all the patients. Regular use of aspirin for the past one year was also ascertained at the time of interview. Patients were interviewed by a trained social worker. Dietary history data were ascertained through interview, asking usual frequency of consumption of selected foods in food groups: cereals, pulses, roots and tubers, nuts, fresh fruit, fats and oils, green leafy vegetables, and animal products. The usual monthly frequencies of consumption of food sources of eight nutritional factors (protein; vitamins B1, B2, A, C, E; calcium; animal sources), weighted by the relative importance of each food as a source of the particular nutrient, was used to estimate the dietary intake of each of these nutrients. For this purpose, the available food composition table from Netherlands was used as similar table for Indian situation was not available. The data was collected on a standardized data collection form. Concurrent reliability and quality control checks were made by the investigators throughout the study. Quality control checks were also made with regard to blood pressure and random blood sugar estimations.
Statistical analysis was performed in stages. In stage I, all the variables were analysed individually by a univariate logistic regression technique. In stage II, variables found marginally significant (P<0.1) in stage I were analysed in a stepwise manner using multiple logistic regression to arrive at the independant factors associated with cataract. Age and sex were included as confounders at each stage of the analysis. For dietary analysis, the scores used in the India-US study on senile cataract were adopted.
| Results|| |
Univariate logistic regression analysis (Stage I) revealed variables such as 10 mm increase in systolic blood pressure, history of consanguinity, tobacco chewing, use of cheap cooking fuel (cow dung, wood, coal and kerosene), non-vegetarian food and more number of meals per day as risk factors in the development of a senile cataract. On the other hand, variables like 10 cm increase in height, 10 kg increase in weight, 1 SD increase in Wt/Ht (Quetelets index), one level increase in education, one level increase in income, utilization of cooking water, 1 SD increase in dietary protein, Vit. B1, Vit. B2, Vit. A, Vit. E, Vit. C, Calcium and food of animal origin were considered to be protective against cataract formation [Table:1a], [Table:1b], [Table:1c].
In stage II, all significant variables from stage I were put into a mu1tivariate model of multiple logistic regression analysis. Both step up and step down analysis gave similar results. Only two variables, 10 mm increase in systolic blood pressure (OR=1.19) and more number of meals per day (OR=1.66) were considered as risk factors. Protective variables were 10 kg increase in weight (OR=0.77), one level increase in education (OR=0.69), one level increase in income (OR=0.63), and utilization of cooking water (OR=0.26) [Table - 2].
| Discussion|| |
The development of cataract is a complex, multifactorial process. The human lens normally undergoes changes with age; it slowly increases in size as new lens fibers develop throughout life; older lens fibers in the depth of the lens become dehydrated, compacted, and sclerosed; a yellow brown pigment accumulates. The yellow brown pigment may become so dense as to constitute nuclear sclerosis and later brunescent cataract. Cortical cataract, however, is the development of vacuoles and water clefts in the lens cortex that tend to increase in extent and in the advanced state give the lens a pearl like appearance. Biochemically, great increases in Na+ ions and water are accompanied by losses of K+ ions, free amino acids, glutathione, inositol and soluble lens proteins in mature cataracts. Marked increases in Ca2+ ions and the insoluble lens proteins are often found in mature cataracts. The present case control study has identified risk as well as protective factors in senile cataract. Presence of a risk factor makes an individual more vulnerable to the development of a cataract. On the other hand, protective factors may play some role in suppressing or delaying the progression of a cataract. Like previous studies,,, we found a strong association between lower education and cataract which may probably be related to socio-economic status. Cataracts were more common among persons who were not utilizing cooking water, ignoring the importance of various nutrients it contains. It again points towards their poor literacy level. Patients in the low income group tended to have more cataracts. Similarly, cataracts occurred more often among patients with lower body weight. Therefore, one might speculate that economic status has some role in the causation of senile cataract, because a higher socio-economical status usually means higher educational and nutritional levels. Previous studies, have reported a relationship between nutritional status and cataract. There was an increased risk of cataract formation with low frequency of protein consumption. The proportion of insoluble protein in the lens of undernourished patients was significantly increased compared to well-nourished patients while the total proteins remained unaltered, suggesting an increased insolubilization process. Further studies involving protein fractionation suggested that poor nutritional status in cataract patients accelerates the insolubilization process. Thus, in general, patients with higher nutritional level have less risk of cataract development. However, risk factors like more number of meals per day does not reflect the nutritious ingredients in the food consumed. This needs to be kept in mind before interpreting the importance of this significant variable in the present study.
A positive correlation between higher systolic blood pressure and cataract has been described by several investigators.,, Hiller et al found the association with posterior subcapsular cataract whereas the India-US study found the propensity towards nuclear and mixed cataracts. As to whether normalisation of elevated blood pressure will minimise the risk of cataract needs to be evaluated by further studies.
This study did not show any correlation between cataracts and aspirin usage. Sheila et al also pointed out that large doses of aspirin, or frequent use of aspirin did not prevent or retard the growth of lens opacities. However, the India-US study found that use of one or more aspirin tablets per month compared with less frequent use, reduced the risk of posterior subcapsular and mixed cataracts. On the other hand, a clinical trial among healthy male physicians reported no apparent reduction in the incidence of cataracts in the aspirintreated group. Further studies may be necessary to determine the association between cataract and aspirin usage.
Though various factors have been attributed to the development of senile cataract, the factors that trigger the process and govern its progress at a given time remains to be explored. It appears clear that development of a senile cataract is a complex, multifactorial process and in all probabilities, is the cumulative effect of exposure to various stimuli in one's life time.
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[Table - 1], [Table - 2], [Table - 3], [Table - 4]