Findings from a study recently published in Acta Ophthalmologica evaluated if exposure to air pollution increases the risk of requiring cataract surgery.
Give me some background first.
Cataracts are the leading cause of blindness worldwide. Their development is multifactorial, including oxidative stress.
Bringing in air pollution: This can exacerbate oxidative stress, overwhelming the lens’s antioxidant defenses and accelerating cataract progression, often requiring surgery for treatment.
- In regards to this research: While previous studies have linked high nitrogen dioxide (NO2) levels to cataracts, they did not explore varying pollutant concentrations or account for ultraviolet (UV) exposure.
Now, talk about the study.
In this study, investigators collected data from 829 participants over the age of 65 (mean age: 72.6) from Bordeaux, France.
About these participants: Patients were evaluated over an 18-year period, from 1999 to 2017, and underwent an ophthalmic history and eye exam every 2 years.
The study details: Investigators followed progression of cataracts and need for cataract surgery, assessing the relationship between air pollution exposure and cataract surgery incidence.
Tell me more about this air pollution exposure component.
The different air pollutants considered for an association with cataract surgery incidence included:
- Particulate matter ≤2.5 μm (PM2.5)
- Black carbon (BC)
- NO2
The average air pollution exposure in the decade prior to the start of the study was estimated based on participants' geocoded residential address.
Plus: Data collected based on cataract incidence were then adjusted for confounding variables such as:
- Diabetes
- Smoking status
- Asthma
- Hypertension
- Body mass index (BMI)
- UV radiation
Findings?
Of the 829 participants, 507 had undergone cataract surgery during the follow-up period.
What the data revealed: Exposure to a 10-year average of NO2 levels above 40 μg/m3 had a 50% increased risk of undergoing cataract surgery.
- The study also found no relationship to cataract incidence and exposure to particulate matter or black carbon.
So how did this study compare to previous?
This study’s long-term design with follow-ups conducted over 18 years was more advantageous than previously-conducted trials in this area.
Data collection methods were also improved by using a Land Use Regression (LUD) model to estimate air pollution exposure, along with adjustments for weather and geography, which enhanced the accuracy of long-term exposure data based on residential addresses.
Any notable limitations?
A few. Among these included:
- The date of cataract surgery was self-reported.
- However, to reduce recall bias, information was consistently collected during follow-ups.
- Some participants may have needed cataract surgery but did not undergo it
- This is interesting, as cataract surgery is fully covered by insurance in France, eliminating the cause of this due to socioeconomic status.
- Small sample size and geographically-limited scope of the study may have affected the findings, restricting the range of air pollutant exposure considered
- This may explain why no association was found between particulate matter and cataract incidence in this study, while the study conducted in England did find a correlation
Anything else should we know?
In discussing the study data and its relation to prior research in this area, authors noted that pollution increases the levels of reactive oxygen species (ROS) and that proteins such as crystallins are key to maintaining lens clarity
- However: These proteins are also susceptible to oxidative damage.
Thus: ROS can damage crystallins through aggregation and crosslinking, leading to lens opacity, as well as damage membrane lipids in the lens—which further reacts with proteins, worsening the damage.
The authors further added that ROS can damage DNA, impairing the repair and replication of lens cells, leading to cell death and further structural damage.
- Take note: All of these factors can contribute to cataract formation.
Take home.
Exposure to NO2 greater than 40 μg/m3 was significant in increasing the risk of cataract surgery.
However: Further exploration of environmental factors, including air pollutants, is crucial for educating the public on how these factors can influence the progression of cataract development.
Such efforts are also key to implementing regulations that control pollution levels and improve quality of life by slowing cataract development.