Epidemiological studies tend to be concentrated around regions where a particular disease is most prevalent. For example, many autoimmune diseases are found in the global north, so the area is hence of interest to epidemiologists.
Epidemiological studies can also be conducted with national boundaries in mind. For example, the Centers for Disease Control and Prevention (CDC) conducts epidemiological studies in the US and gives national healthcare advice based on its findings. The advantage of tracking the prevalence of a disease nationally is that it makes it easier for public health decision-making to be made at a national level.
In an ideal world, epidemiological studies should always be conducted on a global scale. The reason for this is straightforward: if a part of the world is an outlier in terms of the prevalence of a disease, it naturally begets curiosity as to why this is the case. Are there risk factors or lifestyle factors associated with that specific part of the world? Do genetics play a role? The quest to answer these questions will help bring us closer to the underlying causes of a disease if they are not already known.
In this article, we will compare 2 epidemiological studies conducted on Pompe disease in various countries.
A Wide Disparity in Reported Occurrence Rates
In Molecular Genetics and Metabolism Reports, Park attempted to estimate the genetic prevalence of Pompe disease based on data from the Genome Aggregation Database, which contains a huge amount of genetic information. The study also utilized locus-specific databases, which have information regarding both the genotype and clinical severity of a particular disease.
Park discovered that the incidence of Pompe disease according to live births is estimated to be:
- 1:14,000 among African Americans
- 1:40,000 in the Netherlands and the United States
- 1:145,000 in Australia
- 1:600,000 in Portugal.
However, in countries with newborn screening programs, the reported incidence of Pompe disease is much higher, the study showed:
- 1:8684 in Austria
- Between 1:10,152 and 1:27,581 in the US
- 1:44,000 in Hungary
Park’s findings in this study suggest that the prevalence of Pompe disease is more widespread than previously acknowledged. They also highlight the importance of newborn screening programs for Pompe disease.
Read more about Pompe disease epidemiology
Why are so many countries still dragging their feet in implementing newborn screening for Pompe disease? Every country has different healthcare priorities; perhaps some have decided that the cost outweighs the benefit. In addition, epidemiological data on the prevalence of Pompe disease may be unavailable, making the scale of the problem appear less serious than it actually is.
A Close-Up Look at LOPD in Belgium
The second study we will review, published in the Orphanet Journal of Rare Diseases, is far more targeted; it examined the epidemiology of one type of Pompe disease, late-onset Pompe disease (LOPD), in one country, Belgium. Vanherpe and colleagues collected data from 7 neuromuscular reference centers in Belgium and selected patients (n=52) who had LOPD, according to the Pompe disease registry.
They reported that the estimated prevalence of LOPD in Belgium is 3.9 per million, in a population of around 11.4 million people. The mean age of symptom onset was 28.9 years; only 2 patients had symptom onset before 1 year of age.
As expected, two-thirds of patients reported limb-girdle weakness as the initial symptom of their disease. This was either the sole presenting symptom or was reported in combination with other abnormalities, such as axial weakness, fatigue, or respiratory weakness. A third of patients reported respiratory problems as their initial presenting symptom.
Read more about Pompe disease patient education
In Belgium, the most common therapies for LOPD are reimbursed. These include enzyme replacement therapy (ERT) as well as supportive therapies such as physiotherapy and noninvasive ventilation. All patients in the cohort studied were treated with ERT, except for one, due to old age and advanced clinical stage of the disease. The mean age at which enzyme replacement therapy was initiated was 41.2 years.
“Awareness (of) LOPD should even be further increased, as we found a long diagnostic delay as described in other populations,“ Vanherpe et al wrote. “As ERT is more effective in the beginning of the disease, early start of therapy is important.”
Another interesting finding is that all patients in the cohort were compound heterozygotes, meaning that none carried the homozygous mutation in GAA. However, these patients were not initially diagnosed genetically; a reduction in GAA enzymatic activity in muscle and blood tissue was the key factor in their diagnoses.
The Need for More Data
Although a fair amount of epidemiological data is presented in these studies, global epidemiological information on Pompe disease is still lacking.
“In developing nations like India, testing for rare phenotypes including Pompe disease is lacking due to inadequate awareness, coupled with the limited availability of enzyme replacement therapy,” Puri et al wrote in Neuromuscular Disorders. “The latter limits the interest for the busy neurologist, pulmonologist or physician.”
Ideally, one epidemiological study should prompt more to be conducted; this way, we can have a strong set of data in a relatively short amount of time. Increasing public awareness of the importance of epidemiology can also spark positive change.
Park KS. Carrier frequency and predicted genetic prevalence of Pompe disease based on a general population database. Mol Genet Metab Rep. 2021;27:100734. doi:10.1016/j.ymgmr.2021.100734.
Vanherpe P, Fieuws S, D’Hondt A, et al. Late-onset Pompe disease (LOPD) in Belgium: clinical characteristics and outcome measures. Orphanet J Rare Dis. 2020;15(1):83. doi:10.1186/s13023-020-01353-4
Puri RD, Setia N, N V, et al. Late onset Pompe Disease in India – beyond the Caucasian phenotype. Neuromuscul Disord. 2021;31(5):431-441. doi:10.1016/j.nmd.2021.02.013
Löscher WN, Huemer M, Stulnig TM, et al. Pompe disease in Austria: clinical, genetic and epidemiological aspects. J Neurol. 2018;265(1):159-164. doi:10.1007/s00415-017-8686-6