Risk factors for age-related macular degeneration in a Maltese hospital population

Abstract

Background: Age-related macular degeneration (AMD) remains the prevailing cause of blindness among elderly persons living in industrialized countries. As a consequence of population ageing and with the ongoing treatment of cataracts, it is estimated that AMD will become ever more important as an eye condition which determines quality of life in the later stages of existence. It remains an irreversible disease, without an effective cure despite the large number of epidemiological studies conducted. Aim: This study aims to examine those risk factors in an elderly (55+) Maltese hospital population that have a strong to moderate association with AMD, namely history of cigarette smoking, previous cataract surgery, history of cardiovascular disease and hypertension. Method: A hospital-based population was used to recruit cases and controls in a 1:1 ratio. 41 patients diagnosed with AMD were compared with 41 controls. A structured interview was used to collect the data that was analysed using SPSS version 22. A 3-step process was used to identify the risk factors associated with AMD. In step 1 each risk factor was included separately in a univariate analysis. In the second step the associations (odds ratios) were adjusted for age and gender. Those risk factors with a p-value less than the 0.05 level of significance in step 2 were retained and entered into an automated 'stepwise' entry method using binary logistic regression (step 3). Results: This study showed a statistically significant association between AMD and age (odds ratio (OR) for those 55 to 65 years vs. those over 75 years 0.11, 95% confidence interval (CI) 0.03 - 0-43, p-value (P) <0.00), gender (OR for males vs. females 3.03,95% CI 1.12 - 8.19, P = 0.03), diabetes (OR for yes vs. no 5.14,95% CI 1.65 - 15.98, P <0.00), and iris colour (OR for light vs. dark 4.55, 95% CI 1.49 - 13.85, P<0.00). We have been unable to demonstrate any association between AMD and smoking, previous cataract surgery, cardiovascular disease and hypertension. Conclusion: This study has demonstrated a strong association between AMD and age, gender, diabetes and iris colour. Interpretation of the results found in this case-control study conducted on a Maltese hospital population should be considered within the context of the study's small sample size and other limitations. Most risk factors should be confirmed by larger prospective studies. More robust evidence, which currently lacks for most risk factors, except age and smoking, will then warrant, were ethically possible, the conduction of study designs higher up in the hierarchy of research evidence, i.e. randomized controlled trials.