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Multivitamin Supplementation for Cataract Prevention: A Case-Control Study

Multivitamin Supplementation for Cataract Prevention: A Case-Control Study. ASMPH 2012 Group 6 Abad, Imperial, Javate, Palma, Uy R, Valencia. Introduction. Age-related cataract - Leading cause of blindness ~17 million (Congdon, 2001)

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Multivitamin Supplementation for Cataract Prevention: A Case-Control Study

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  1. Multivitamin Supplementation for Cataract Prevention: A Case-Control Study ASMPH 2012 Group 6 Abad, Imperial, Javate, Palma, Uy R, Valencia

  2. Introduction • Age-related cataract - • Leading cause of blindness • ~17 million (Congdon, 2001) • 500,000 of the population is blind, of these 62% (310,000) is due to cataract (Philippine Information Agency)

  3. Significance of the Study • Evaluating advertising claims for multivitamins • Finding a modifiable preventive factor for cataract • Delay onset by 10 years  reduce need for surgery by half (Congdon, 2001) • Focusing on the elderly: An ever-increasing, undervalued population

  4. Review of Related Literature Oxidative Insult  Cataract Formation (Head, 2001) A Possible Protective Role? Antioxidants: Vitamins A, C, E Riboflavin – Glutathione Reduction Possibly Vitamin B5, Folate, Selenium

  5. Review of Related Literature:A Role for Multivitamins? YEA • OR =0.84 (AREDS, 2006) • OR= 0.83 (Clinical Study Group, 2008) • OR = 0.6 (Kuzniarz, 2001) NAY • (AREDS, 2001) • (Gritz, et al., 2001) • (West, 2000) • (Seddon, 2007

  6. Conceptual Framework

  7. Objectives • General • To determine if multivitamin intake among ophthalmologic patients in the Philippines is a protective factor in the development of cataracts • Specific 1. To determine the proportion of patients with cataract who take and do not take multivitamins 2. To determine the proportion of patients without cataract who take and do not take multivitamins 3. To determine if there is an association between multivitamin intake and cataract development controlling for the effect of the following: age, group, sex, level of education, smoking profile, and body mass index (BMI).

  8. Research Design: Case Control

  9. Description of Study Population • Two private ophthalmologic clinics (Manila and Cabanatuan) and OPD of a public hospital in Manila • Case - any patient aged 55 years old and above, who had been diagnosed by a doctor to have cataract in at least one eye • Control - a patient aged 55 years old and above, who had no cataract in any eye based on doctor’s diagnosis.

  10. Variables: Operational Definition and Categories • Independent Variable - Multivitamin Intake (+) Multivitamin Intake: regular or frequent intake of any multivitamin supplement for at least 10 years prior to diagnosis or consultation (-) Multivitamin Intake: inconsistent/infrequent or no intake of any multivitamin supplement for at least 10 years prior to diagnosis or consultation

  11. Variables: Operational Definition and Categories • Dependent Variable: Cataract • Having a diagnosis of a cataract in either or both eyes of the patient, assessed by an ophthalmologist via a slit lamp examination or other diagnostic tools for cataract detection

  12. Variables: Operational Definition and Categories • Potential Confounding Variables • Age • Sex • Educational Attainment • Smoking • Body Mass Index

  13. Sample Size Estimation • Epi Info™ Version 3.5.1 • Assumptions: • 90% level of confidence • 80% power • 2:3 ratio between the two groups • 50% expected frequency of exposure in the not ill group • 0.6 odds ratio • Computed: 260 cases and 174 controls • Actual: 260 cases and 187 controls

  14. Sampling Design • Quota sampling • Identification of Cases (with cataract) and controls (without cataract) through interview • Validation through medical records (if necessary)

  15. Data Collection Tool • Primary Data • Query (Face to face interview) • Multiple interviewers - standardized interview behavior • Secondary Data (for validation) • Medical records of participants

  16. Potential Biases and Methods to Minimize them • Selection Bias - caution in making generalizations • Source of subjects • Non-response • Information bias • Recall bias - sufficient probing during interview • Hawthorne effect - blinding • Confounding - stratified analysis

  17. Data Processing and Statistical Analysis • Completeness and consistency of interview sheets • Verification if necessary • Double encoding • Analysis • cOR at 95% and Pearson's chi square value • Stratified analysis - Mantel Haenszel value • Multiple Logistic Regression • Wald test

  18. Ethical Considerations • Informed consent • Interview form sheets coded only by the research team members • Possible commercial value

  19. Limitations of the Study • Time constraints • Readjustment of sample size

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