A recent study published in the American Journal of Ophthalmology is proposing an inexpensive fat measurement tool—the visceral fat metabolism score (METS-VF)—as a way to more accurately assess cataract risk.
Give me some background first.
While cataracts are known to be caused by aging, multiple external factors like obesity, hypertension, smoking, diabetes, sex, and ethnicity also contribute to their development.
Looking specifically at obesity: This has a strong correlation with cataract risk, secondary to excessive adipose tissue-induced oxidative stress and inflammation.
And although body mass Index (BMI) is used to assess obesity, it does not accurately evaluate visceral fat distribution (a significant health risk factor). Conversely, METS-VF does.
- To note: METS-VF is calculated using the metabolic score for insulin resistance (METS-IR), waist-to-height ratio (WHtR), age, and sex.
Now, talk about the study.
In this cross-sectional study, researchers examined data collected between 1999 and 2008 by the National Health and Nutrition Examination Survey (NHANES), an ongoing research survey program that evaluates both overall and nutritional health in the United States.
- The researchers were able to calculate METS-VF for each participant using this data.
Then: Through various analysis methods, the researchers also assessed how METS-VF compared to traditional obesity markers when it came to correlations with cataract prevalence.
Who was included in the study?
The study included 2,730 U.S. adults with data on factors such as: cataracts, hypertension, fat, education status, age, sex, ethnicity, alcohol consumption, smoking status, poverty income ratio, and daily intake of calories/protein/carbohydrates/fat.
Notably: Of those 2,730 participants—290 had cataracts.
So what did they find?
Researchers discovered that the mean METS-VF was 6.03 ± 0.62 in non-cataract patients and 6.48 ± 0.38 in cataract patients.
- The METS-VF scores were indexed into quartiles, where the lowest scores were in Q1 (the reference level), and the highest scores were in Q4.
Additionally: Logistic regression revealed that as METS-VF increased, the prevalence of cataracts within each quartile also increased.
- Q1: 1.90%
- Q2: 6.74%
- Q3: 10.25%
- Q4: 23.61%
Even after adjusting for age, race, and lifestyle habits, the odds of developing cataracts in Q4 were 3.14 times higher than those in Q1 (OR = 3.14, 95% confidence interval [CI]: 1.67–5.93).
Tell me more.
During subgroup analysis, after adjusting for age, race, and lifestyle habits, the association between METS-VF and cataract prevalence was found to be stronger among:
- Individuals aged 59-85 (OR = 2.71)
- Male individuals (OR = 3.72)
- Non-Hispanic Black individuals (OR = 4.04)
- Individuals with education levels above high school (OR = 4.75)
- Individuals with moderate physical activity (OR = 3.67)
- Alcohol drinkers (OR = 3.02)
- Individuals without hypertension (OR = 3.14)
- Individuals with a poverty-to-income ratio greater than 1 (OR = 2.96)
Go on …
Significant non-linear relationships were not observed between cataract development and scores across all of the traditional obesity markers: BMI, waist circumference (WC), waist-to-height ratio (WHtR), and METS-VF.
Interestingly: Based on Area Under the Curve (AUC) values, METS-VF (0.7432) outperformed BMI (0.5428), waist circumference (0.5227; WC), and WHtR (0.5729) in diagnostic accuracy for cataracts.
- What this suggests: METS-VF may better predict cataract development while also highlighting the impact of visceral fat on cataracts.
Limitations?
A few… among them:
The study’s cross-sectional design limits firm conclusions on cause and effect.
Additionally: The determination of cataract diagnosis was based on self-reported history of cataract surgery, which may have underestimated actual cataract prevalence.
Expert opinion?
The researchers stated that METS-VF could be a useful biomarker for cataract prevention, due to its strong predictability of cataracts.
They added that further research is still needed to investigate these associations and identify potential mechanisms connecting visceral fat distribution and cataract development.
- In all: By providing a clearer picture of visceral fat’s impact on cataract development, METS-VF may help healthcare providers identify at-risk individuals earlier and recommend targeted lifestyle interventions in a cost-effective manner.
Take home.
METS-VF shows promise as a superior alternative to BMI in predicting cataract risk. By identifying individuals with elevated METS-VF, clinicians may be able to take proactive steps to improve eye health and reduce the burden of cataracts.
As such: Providers should begin calculating METS-VF as a complementary metric to assess cataract risk in their patients.