Multivitamin Supplementation and Cataract A Case-Control Study ASMPH 2012 Group 6 Abad, Imperial,...

Multivitamin Supplementation and Cataract

A Case-Control Study

ASMPH 2012 Group 6Abad, Imperial, Javate, Palma, Uy R, Valencia

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)

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

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

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

Conceptual Framework

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).

Research Design: Case Control

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.

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

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

Variables: Operational Definition and

Categories

• Potential Confounding Variables– Age– Sex– Educational Attainment– Smoking– Body Mass Index

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

Sampling Design

• Quota sampling • Identification of Cases (with cataract) and

controls (without cataract) through interview

• Validation through medical records (if necessary)

Data Collection Tool

• Primary Data– Query (Face to face interview)• Multiple interviewers - standardized

interview behavior

• Secondary Data (for validation)–Medical records of participants

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

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

Ethical Considerations

• Informed consent• Interview form sheets coded only by

the research team members• Possible commercial value

Limitations of the Study

• Time constraints – Readjustment of sample size

Results

Distribution of cases and controls of cataract according to intake of multi-vitamins from two private ophthalmologic clinics in Manila and

Cabanatuan, and an outpatient department of a public hospital in Manila

Multivitamin Intake

(+) Cataract (-) Cataract Total

(+) Multivitamin

intake

124 78 202

(-) Multivitamin intake

136 109 245

Total 260 187 447

•260 cases: 61.4% multivitamin users•187 controls: 55.5% multivitamin users

Results

• Odds ratio: .27 (90% CI = 0.93 – 1.75) -> not significant

• Therefore, multivitamins not protective of cataract development

• Stratified analysis for confounders: none of the variables can be considered a confounder

Distribution and stratified analysis of cases and controls according to age, sex, educational attainment, smoking status,

and BMI

Distribution and stratified analysis of cases and controls according to age, sex, educational attainment, smoking status,

and BMI

Results

• Logistic regression: assessment of the effects of multivitamin intake, age, sex, education, smoking status, and BMI on the development of cataract

• Only age showed a significant contribution

Table 4. Logistic Regression Analysis of the Effect of Multivitamin Intake, Age, Sex, Education, Smoking Status, and

BMI on the Development of Cataract

Sig. OR 90% CI

Multivitamin

Intake

0.45 0.84 0.58-1.22

Age 0.00 0.52 0.45-0.59

Sex 0.50 0.83 0.53-1.30

Education 0.95 1.01 0.80-1.27

Smoking Status 0.24 0.68 0.39-1.16

BMI 0.79 0.97 0.81-1.17

Discussion of Results

Discussion of Results

• multivitamins intake may not have a protective effect from cataract

• Studies with similar results:– Gritz and colleagues randomized controlled trials• Excellent reference

– Age- Related Eye Disease Study– May be due to unbalanced diets

Discussion of Results

• Stratified analysis– level of education: elementary level gave a

statistically significant confidence interval -> low level of education increased the odds of developing cataract with multivitamin intake• may be due to inadequate knowledge on health, lack of

proper diet or improper intake of multivitamins

Discussion of Results

• Why the rest are not confounders?– recall bias: sole contributory factor for these results• first, overestimation or underestimation of data reporting• second, false information was given

• Logistic regression: aging is significant and contributory to the development of cataract– Aging is the primary risk factor while age, sex,

smoking status and BMI are contributory risk factors

Discussion of Results

• One must be careful about multivitamins and their claims; practice vigilance

• Not prudent for one to rely solely on multivitamins for health promotion and disease prevention

Conclusions

• Multivitamin supplementation does not confer protection against the development of cataract among ophthalmologic patients in the study.

• Stratified analysis of the data reveals that none of the different variables considered, which include age group, sex, level or education, smoking status, and BMI proved to be a confounder.

Recommendations• Recommendation for a cohort study– future investigations regarding the protective

influence of multivitamin supplementation

• Recommendation for a randomized controlled trial

• Standardizing the multivitamins being taken as well as the frequency of consumption

• Daily nutritional intake must be noted• Categorizing the participants into the different

cataract kinds