Autism & Mitochondrial Disease: Investigating Mortality Rates

What's curious, if this 'pool' of people with mitochondrial disease (with autism or autistic features) does exist, how is their health? Their mortality rate hasn't been altered, even a little? Even if the argument is made that this 'pool' of people would have a less severe form of mitochondrial, it would generally accepted that a person with mild mitochondrial disease would still be at a greater risk of associated diseases, raising the mortality rate.

A study done by Baylor College of Medicine, Texas Children's Hospital, State University of New York, Georgetown University, and Stanford University concluded this:

Patients with cardiomyopathy had an 18% survival rate at 16 years of age. Patients with neuromuscular features but no cardiomyopathy had a 95% survival at the same age. Conclusions. This study gives strong support to the view that in patients with RC defects, cardiomyopathy is more common than previously thought and tends to follow a different and more severe clinical course. Although with a greater frequency than previously reported, mitochondrial DNA mutations were found in a minority of patients, emphasizing that most mitochondrial disorders of childhood follow a Mendelian pattern of inheritance.

According to documented studies, the mortality rate amongst autistic individual is 3.4% (about double the expected rate). It must be noted that the deaths were attributed to choking (while unattended), pneumonia, and meningitis for institutionalized individuals. Those living independently or with their parents, one died following an epileptic attack, two others were from drug overdoses.

Another study, the largest ever done on autism and mortality, also concluded the mortality rate to be about double that of the general population. One could possibly draw the conclusion that the individuals who died while institutionalized, might have had a mitochondrial disorder. Perhaps that is why there were at risk and subsequently died from lung and breathing issues. That would still be a very small percentage--roughly 1.7%--of autistic people who might have an underlying mitochondrial disease. That is a fairly baseless conclusion, though, given that the same study concluded that individuals with more severe mental retardation had a three-fold increase in deaths from all causes (except cancer). So, no one is to say whether those 4 people died simply as a result of poor care or treatment in an institution or by an undiagnosed mitochondrial disease. There are too many variables. Either way, we are still looking at a relatively low rate of mortality, as opposed to the rate for individauls with mitochondrial disease (as high as 10-50%, depending on diagnosis, see below).

If 10-20% of autistic children (2,667-5,333), were to have mitochondrial disease, how is it that their mortality is absolutely unaffected. Apparently all have milder forms of mito? That none of them have died as a result of their mitochondrial disease? What is the hospitalization rate for autistic children? What is the same rate for children with mitochondrial disease (even mildly affected)?

We can see a trend from this study done by Joseph L. Edmonds, MD; Daniel J. Kirse, MD; Donald Kearns, MD; Reena Deutsch, PhD; Liesbeth Spruijt, MD; Robert K. Naviaux, MD, PhD

Mitochondrial disease followed an episodic course, with periods of stasis or slow developmental progress, punctuated by neurodegenerative events in 18 (60%) of 30 patients. Intercurrent infection was recognized as a precipitant of neurodegenerative events in 13 (72%) of 18 patients with a history of episodic degeneration.

Conclusions Children and adults with mitochondrial disorders are at high risk for hearing loss and life-threatening complications of intercurrent infections. A constellation of audiologic abnormalities, multiorgan system involvement, and history of neuromuscular setbacks with infection strongly suggests mitochondrial disease. Knowledge of these features can lead to more rapid diagnosis and improved medical and surgical management for this special group of patients with fundamental defects in bioenergy metabolism.

I've yet to read about all these autistic children who have lost their hearing or have life-threatening, recurrent infections. So, we are to assume that every single child currently diagnosed with autism but who really has mito, somehow continually dodges the typical symptoms and health issues clearly marked by mitochondrial disease?

Is this worth studying? Yes. Scientists have done some preliminary studies, and they all conclude that further investigations are warranted. I don't think anyone is denying that a small percentage of children currently diagnosed with autism may eventually be diagnosed with mitochondrial disease. But, we must use caution and be careful when people begin to inflate those numbers, and misquote study findings.