A recent study published in The Royal College of Ophthalmologists evaluated the possible connection between gender-based characteristics and myopia development.
Give me some background first.
As the most common refractive disorder and steadily growing, myopia is projected to affect 50% of the world’s population by 2050.
The condition has been associated with a number of different factors, including environmental, genetic, socio-demographic, and anthropometric among others.
Which leads to …
With many intertwining factors involved, researchers decided to investigate the true effect on myopia from height, weight, and body mass index (BMI) as possible sex-specific risk factors.
Now, talk about the study.
In this cross-sectional study, 101,438 participants' data was collected from the databases of the Israeli Defense Forces (IDF). For this study, data was pulled from the country’s northern recruitment center.
All 17-year-olds in the country underwent medical evaluations as part of the draft process, including an eye exam.
Any more population specifics?
Participants with more than one refractive error were excluded.
The study population consisted of 22,326 myopes and 79,112 emmetropes, and the gender breakdown was 57.9% male and 42.1% female, all 17 years of age.
Findings?
Following statistical analysis of the IDF data, the prevalence of bilateral myopia was 19.1% in males and 26.0% in females.
What about BMI?
The researchers stratified the participants into categories of underweight, normal, overweight and obese. Within these strata, they observed the following myopia prevalence:
In young men:
- 20.5% for underweight
- 18.7% for normal
- 20.1% for overweight
- 22.3% for obese
In young women:
- 27.4% for underweight
- 25.7% for normal
- 26.8% for overweight
- 27.6% for obese
And height?
Males in the lower height category were observed to have lower myopia.
In the ≤10th height percentile for males, there was 21.4% myopia prevalence, compared to 18.5% to 19.6% in other height categories.
Female participants did not have this same association.
Now discuss weight.
For both male and female participants, higher myopia prevalence was recorded in both the lower and higher weight percentiles compared to the central categories.
For females, there was 27.5% prevalence in ≤10th weight percentile, compared to 27.7% in the ≥90th percentile and 25.5% in other weight categories.
For males, there was 20.4% prevalence in ≤10th weight percentile, compared to 21.4% in the ≥90th percentile and 18.7% in other weight categories.
Expert opinion?
Per the authors of the study:
“Although we observed no significant interaction of height and BMI, the increased risk for bilateral myopia in the lower height decile—overall and within the same BMI group (from normal to obesity)—warrants further research.”
Limitations?
There is possible underrepresentation in certain populations that would not be included in the draft examinations.
In IDF-based studies, the following are typically not included:
- Secular Jewish mothers
- Pregnant or married females
- Ultra-orthodox Jewish
- Certain minority groups
Take home.
The authors concluded, “A higher risk for bilateral myopia was associated with either BMI solely or height and weight, as well as pre-hypertension, in males.
They added that further research would be necessary to fully confirm the association.