Original
Although death rates in ME appear to be quite low, this may be because death is frequently attributed to other causes.
Studies available are small, and few. The good news is that there have been recent advances in research and funding. A few small studies are still better than nothing.
At least one study by Dr. Leonard A. Jason (http://www.tandfonline.com/doi/full/10.1080/21641846.2016.1236588?src=recsys) did find the life expectancy of someone with ME may be significantly shorter (55.9 years) ralative to the overall US population (73.5 years). This is especially so for cardiovascular (heart) related causes. Suicide rates may also run quite high (several times national averages), especially where there is a lack of support from doctors.
Possibly due to immune system problems, infections and cancer may also be of concern. This can be especially so in extreme cases where muscles weakness can contribute to difficulties with swallowing, leading to aspiration. (http://www.telegraph.co.uk/news/health/10137694/Emily-didnt-only-have-ME.html)