A recent study published in Ophthalmology and Therapy assessed the trends and cross-country inequalities of the global trachoma burden from 1990 to 2021 and estimated its burden to 2040.
Give me some background.
Trachoma is a chronic form of conjunctivitis caused by recurrent infection with specific strains of Chlamydia trachomatis.
- If left untreated, it can progress to corneal opacity and blindness.
Despite global efforts to eliminate trachoma, trachoma remains the leading infectious cause of blindness and a public health concern in many countries.
- In fact: 125 million people still live in trachoma-endemic areas and face the risk of trachoma-related blindness.
Even further: The study authors from this investigation noted that as a “neglected tropical disease,” few studies have comprehensively investigated its disease burden, such as its geographic distribution and health inequalities.
Now, talk about the study.
Investigators extracted data on the prevalence and disability-adjusted life-years (DALYs) of trachoma from the Global Burden of Diseases Study (GBD) 2021 database.
- Note: The GBD 2021 data was obtained from the Global Health Data Exchange (GHDx) website, which provides high-quality disease data on the burden of 371 diseases and injuries in 204 countries and territories worldwide.
Using this data, the research team reported epidemiological characteristics of trachoma at the global, regional, and national levels.
Give me a refresher on DALYs.
DALY is a summary indicator that combines time lost to premature death and time lived in a less-than-ideal state of health (collectively referred to as “disability”), the study authors explained.
How this was calculated: By summing the years of life lost (YLLs) and years lost due to disability (YLDs) attributed to visual impairment caused by trachoma.
- In other words: Each DALY related to trachoma was equivalent to 1 year of healthy life lost due to the disease.
Findings?
Globally, 1,414,047 people were estimated to have trachoma in 2021—with an age-standardized rate (ASR) of prevalence of 16.37 per 100,000 population.
- Note: ASR is a weighted average of the age-specific mortality rates per 100,000 people, that accounts for the differences in age structure of the populations being compared.
Between 1990 and 2021, the prevalent cases and DALY numbers of trachoma decreased by 30.2% and 34.4%, respectively.
So what drove the reduction in trachoma cases?
Namely global epidemiological changes, wherein countries with lower sociodemographic indices (SDIs) disproportionately bore the heaviest burden.
- Interestingly: These epidemiological changes masked the increase in trachoma burden caused by population aging and growth.
However: While the prevalence and DALY rates are projected to decrease from 2022 to 2040, the prevalent cases and DALY numbers are actually expected to increase.
- Meaning: Though there is a projected decline in trachoma prevalence by 2040, the number of patients with trachoma is expected to increase.
Talk about the geographic distribution of trachoma.
At the regional level, Eastern Sub-Saharan Africa had the highest burden of trachoma in 2021, with 25.7 times the ASR prevalence of trachoma compared to the global level (420.59/100,000 vs. 16.37/100,000).
Contributing factors responsible for the widespread transmission of trachoma in Eastern Sub-Saharan Africa were as follows:
- Poor sanitation conditions
- Inadequate awareness of trachoma
- Economic constraints
- Limited access to medical care
And the top three countries with the highest number of trachomas cases in 2021 were:
- Ethiopia (552,129)
- India (356,503)
- Somalia (103,882)
Expert opinion?
The study authors note that trachoma has long been considered a “disease of poverty,”—and previous studies have reported strong associations between trachoma and indicators of poverty.
They explained that “the relationship between poverty and trachoma is more intricate, potentially involving bidirectional causality,” as poor hygiene conditions, inadequate awareness, and limited medical resources that stem from poverty can contribute to greater risk of trachoma.
On the other hand: Productivity loss in patients with trachoma-induced blindness and medical expenses associated with trachoma can both exacerbate poverty.
Anything else?
The authors also highlighted that women have consistently shouldered a heavier trachoma burden than men due to gender roles—not biological differences.
Meaning: As women predominantly take on the role of caregivers, they are exposed more frequently to unsanitary environments and contaminated water sources—making them more susceptible to trachoma infections.
Limitations?
These included:
- The burden estimates for some underdeveloped countries with limited resources may be underestimated due to potential under-registration of trachoma data
- While advanced disease models were developed by GBD investigators, variations in the quality of raw data across countries may have caused bias
- Since DALYs were calculated on the basis of chronic ocular conditions i.e., visual impairment, DALYs caused by trachoma without visual impairment may have been ignored—leading to an underestimation of the disease burden
- As the data was up to 2021, the latest trends in the global burden of trachoma have not yet been studied
Take home.
These findings demonstrate that over the past three decades, the global burden of trachoma has decreased significantly, but SDI-related inequalities between countries have persisted.
From 2022 to 2040, the prevalence and DALY rates of trachoma are projected to continue the downward trend.
However, the number of patients with trachoma and trachoma-related DALYs are predicted to further increase.
Next steps?
As the number of patients with trachoma is estimated to increase, the investigators advocated for:
- Prevention control strategies tailored to the specific needs of different regions and populations
- Continued monitoring and evaluation of trachoma control programs to ensure their effectiveness