Epidemiology (The WHO)

Last week I gave an introduction to the blog and the importance of learning about Long QT Syndrome (abbreviated here as LQTS). This week’s blog will focus on the epidemiology of LQTS. When we ask ourselves the who, what, where, when, and why of a disease process, epidemiology refers to the WHO. Who gets this disease? Is it children from a specific ethnic background or geographic location? Is it more prevalent in males or in females? Is it genetically passed from parent to child? This blog post will have a lot more number crunching in it…but don’t get too flustered because while a lot of science involves understanding the statistics behind a disease, I generally am more focused on why the numbers matter.

LQTS is under diagnosed because children often only find out that they have the condition once they have had a related cardiac incident or if an EKG was completed during a child’s development. Additionally, parents that are carriers for the genetic mutations that cause this syndrome often do not have any of the worrisome symptoms of LQTS, thus they may have unknowingly transmitted it genetically to their offspring. Because of these issues it is hard to get good data on the big picture of who is getting this disease…but here’s some numbers so that you can understand a general idea of the situation.

Currently LQTS may be expected to occur in 1/10,000 people (Solvari, et al 2014). However another study found the prevalence of LQTS to be up to 1/2000 in Caucasian infants (Schwartz, et al 2009).

There is a higher prevalence (60-70%) of females diagnosed with LQTS to males. As women already have been found to have a longer QT interval then men, this could be one of the key features that predispose women to having the genetic variants that causes LQTS (Locati, et al 1998). Furthermore, Finnish and Norwegian populations have been found to carry more of the genetic mutations that lead to this syndrome (Berge, et al 2008). Lastly, these genetic mutations can be passed on to future children—so it is important for adults with LQTS who are interested in bearing children to work with a physician to help prevent complications.

As demonstrated by the number crunching above, there is a lot of variability in the predicted prevalence of LQTS. Some researchers are concerned about an increase in frequency of diagnosis of LQTS. New studies are looking to understand if the frequency of diagnosis is increasing because more children have the disease, or is it that we are just doing a better job of looking for it before it causes an unexpected problem. You know all those “well child physical exams” that are required prior to participating in a youth sport or activity? Well those screening appointments are often specifically looking for LQTS in our pediatric population.

See you next week for a talk about the pathophysiology (the how it works) of pediatric Long QT Syndrome!

~Until the next beat~
Sarah

Sources:

Berge, K., Haugaa, K, et al. (2008). Molecular genetic analysis of long QT syndrome in Norway indicating a high prevalence of heterozygous mutation carriers. Scand J Clin Lab Invest., 68(5), 362-8. Retrieved from Pubmed, http://www.ncbi.nlm.nih.gov/pubmed?Db=pubmed&Cmd=ShowDetailView&TermToSearch=18752142

Locati, E., Zareba, W, et al. (1998, June 9). Age- and sex-related differences in clinical manifestations in patients with congenital long-QT syndrome: Findings from the International LQTS Registry. Retrieved January 18, 2015, from http://www.ncbi.nlm.nih.gov/pubmed/9631873

Schwartz, P., Stramba-Badiale, M, et al. (2009). Prevalence of the congenital long-QT syndrome. Circulation AHA, 120(18), 1761-7. Retrieved from Pubmed, http://www.ncbi.nlm.nih.gov/pubmed/19841298

Solvari, A. (2014, April 22). Long QT Syndrome  (J. Rottman, Ed.). Retrieved January 18, 2015, from http://emedicine.medscape.com/article/157826-overview#a0156