1) Two age peaks: a fascinating paper confirmed two peaks for when people get ME/CFS: around 16 years old and in the mid thirties. The early onset in adolescence was associated with severe ME/CFS, an infectious onset, and having relatives with the disease. A brief summary...
2) Healthcare data from Norway had previously suggests that Incidence age is bimodal for ME/CFS. This study checked this pattern using two big sources: the DecodeME study and a large European survey with more than 8000 respondents. 3) They tried to fit a unimodal normal curve to the onset data but that didn't fit well (Hartigan's Dip Test was significant). Using three modes also caused problems but if they used a bimodal distribution, the means and standard deviations were almost the same in all countries.
4) In countries such as Norway or the UK the pattern was clearer than in others but overall the data looks quite convincing. The Netherland was a bit of an outlier because it had a much larger peak in adolescence. 5) Approximately 20% of patients falls in the early onset onset group. They were more likely to report an infectious trigger (57%) than the late onset group (47%) and more likely to have glandular fever/infectious mononucleosis as a trigger of their ME/CFS. 6) A larger percentage of respondents in the early onset group had one or more first degree relatives with ME/CFS (22.5%) compared to the later onset group (14.9%). The early onset group also tended to be more severe (see the graph below) but the difference was not that large.
7) Interestingly, there was no difference in sex ratio between early or late onset. Overall, the two groups were quite similar but it's fascinating that there are two age peaks for getting ME/CFS. These tells us something about its cause, although it's not exactly clear what. 8) On the S4ME forum people have been speculating: does it reflect times of high infection/vaccination rates? Or perhaps a change in our immune system or lipid metabolism? Would be interesting to hear other other hypotheses. There must be an explanation for this pattern... 9) Interestingly, the survey data also point to a peak in incidence around 2009-2010, coinciding with the swine flu pandemic. This study was mostly set up by patients - a big shoutout to Simon McGrath and his colleagues for doing this important work. 10) Link to the paper: McGrath et al. Incidence age is bimodal for Myalgic Encephalomyelitis / Chronic Fatigue Syndrome, with higher severity burden for early onset disease. academic.oup.com