A study recently published in the Journal of Glaucoma evaluated the influence of smoking on optic nerve head (ONH) vessel density loss.
Give me some background first.
Glaucoma has noted associated and risk factors for both vascular and mechanical etiologies; however, a link to smoking has remained uncertain.
While numerous studies have investigated and found no associations (see here, here, and here), some have identified a potential connection (see here, here, and here).
Go on…
The authors of this study noted that ONH and macular vessel density have been associated with glaucoma progression.
Their hypothesis: There could be a link between these measures and smoking history.
Now, talk about the study.
This was a retrospective longitudinal study conducted at the University of California San Diego with a mean follow-up time of 4 years.
Participants went through optical coherence tomography-angiography (OCT-A) imaging, and smoking intensity of the participants was measured as the pack-year from the baseline OCT-A.
A pack-year is a measure that multiplies the number of packs of cigarettes smoked per day by the number of years the person has smoked.
Who was included in the study?
Participants were glaucoma suspect and POAG patients from Diagnostic Innovations in Glaucoma Study (DIGS). Selection for the study was determined by selecting patients who:
- Had at least 2 years of follow-up
- OCT-A performed at at least four visits
A total of 164 eyes from 110 patients were included in the study, with 45.5% of the patients having a history of smoking.
Any important outcome measures?
Participant imaging was measured for:
- Circumpapillary RNFL (cpRNFL) thickness
- Whole image capillary density (wiCD)
Linear mixed-effects models were also run for these measures.
Findings?
Among smokers, the mean smoking intensity was 16.5 pack-years. In the univariable model, neither smoking history or intensity had an association with the rates of wiCD or cpRNFL loss.
However, in the multivariate model, smoking intensity was significantly associated with faster wiCD loss (p = 0.048).
Tell me more.
The rate of thinning of wiCD increased significantly when smoking intensity was above 22.2 pack-years, displaying faster ONH vessel density loss.
Smoking intensity also appeared to be associated with cpRNFL loss over time.
Expert opinion?
Per the study authors: “Although the effects of smoking may appear modest, our results highlight its potential role as a modifiable risk factor affecting both structural and vascular factors.”
They continued: “Further investigation is needed to determine if smoking cessation slows the progression of glaucoma.”
Anything else?
Among non-smokers, vessel density loss differed. However, for every additional 10 pack-years of smoking, a 0.1%/year increase in vessel rate loss was observed.
Limitations?
The authors noted that there was no control group in this study, and thus advised caution in generalizing the data to other stages of the disease.
In addition, the smoking information was self-reported—which introduced possible bias. Further, the sample size of the study was relatively small, warranting additional future research.
Take home.
Ultimately, further research is necessary to confirm these findings and continue investigating this link.
The authors of the study concluded that, with greater smoking consumption associated with
faster vessel density, “smoking intensity should be considered when assessing the risk of glaucoma progression, as well as its management.”