Sumayya Ahmad, MD: Demographic Associations With Astigmatism

Developing a greater understanding of associations and risk factors, even among common conditions, can pay great dividends in terms of early identification for physicians and their patients.

That premise is what prompted investigators to examine the demographic characteristics of patients with varying forms of astigmatism.

In order to develop a greater understanding of demographic associations with astigmatism, investigates analyzed keratometry and demographic data from the National Health and Nutrition Examination Survey (NHANES) from 1999 to 2008 using multinomial logistic regression, which adjusted for confounders.

At the conclusion of their study, investigators found multiple demographic associations with differing forms of astigmatism. Based on the results, investigators concluded a 20 to 24 year old had a 20 times higher odds of having with-the-rule astigmatism than an 80 to 85 year old.

Additionally, women (39%), Mexican-Americans (79%) and college graduates (48%) had higher odds for having with-the-rule astigmatism compared to males and non-Hispanic whites with less than a ninth grade education. In summary, there was significantly higher odds of developing with-the-rule astigmatism if a patient was of younger age, had myopia, a lower educational status and was female.

For more on the clinical takeaways from the study, MD Magazine® sat down with study co-author Sumayya Ahmad, MD, assistant professor of ophthalmology at Icahn School of Medicine, at the American Academy of Ophthalmology (AAO) 2019 Annual Meeting in San Francisco.

MD Mag: What were the results of your study into demographic associations into varying forms of astigmatism?

Ahmad: We were interested mostly in the different types of astigmatism and their correlations with different parts of the eye exam and also the rest of the body. So, there is 3 types of astigmatism. There is with-the-rule, against-the-rule, and oblique and they have been demonstrated to be present in certain populations but not in others.

We wanted to see what relationships existed between, let’s say, demographic characteristics like are you African American or Mexican American or Caucasian American? are you more likely to have a certain type of astigmatism versus another race or gender or age.

So the national health and nutrition survey is a really good way to look at population-wide data in the US. Its quickly available, its made by the government, they basically take a representative sample of the US and they go across the country and take every piece of information that you can imagine from people—where they live, how old they are, what they do for a living— and they take it all, they deidentify it and they publish it.

So, people can look at interesting relations between, let’s say, the food they eat and conditions they have or other health problems. We looked this particular data set and we basically did a regression model to see what things were correlated with the different types of astigmatism.

We found that women tend to have more with-the-rule astigmatism, which is hen the cornea is shaped more like a football sitting up. So women have more with-the-rule and men have more (against-the-rule). The trend is also that as people get older they get more against-the-rule astigmatism over time, which we knew but we haven’t actually shown in a population wide study.