{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,20]],"date-time":"2026-06-20T10:36:26Z","timestamp":1781951786426,"version":"3.54.5"},"reference-count":54,"publisher":"Oxford University Press (OUP)","issue":"1","license":[{"start":{"date-parts":[[2026,3,18]],"date-time":"2026-03-18T00:00:00Z","timestamp":1773792000000},"content-version":"vor","delay-in-days":76,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Clare Francis Research Fellowship funded by Action"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"published-print":{"date-parts":[[2026,1,21]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                  <jats:p>Myalgic Encephalomyelitis, or Chronic Fatigue Syndrome (ME\/CFS), is a disease of uncertain origin. Studies of Norwegian health records have suggested that ME\/CFS incidence across age groups is bimodal\u2014a characteristic that could provide insight into the aetiology of the disease. Here, we analysed survey data from over 9000 respondents with ME\/CFS from 10 European countries, and observe an early onset peak with a mean of 16.0\u2009years old (standard deviation [SD]: 4.3) and a late onset peak at 36.6\u2009years old (SD: 10.5). Statistical support for multimodal onset age was evident in 7 of the 10 countries examined. Infection as a trigger for ME\/CFS was 10 percentage points higher among early compared to late onset disease (p\u2009=\u20092.1 \u00d7 10\u221213). Early onset ME\/CFS was associated with greater odds of being severely or very severely affected (OR\u2009=\u20092.15, 95% CI [1.84\u20132.51], p\u2009&amp;lt;\u20092 \u00d7 10\u221216). Those with first degree relatives with ME\/CFS had greater odds of early than late onset ME\/CFS (OR\u2009=\u20091.43, 95% CI [1.25\u20131.63], p\u2009=\u20094.4 \u00d7 10\u221207). We further validated our findings in a UK dataset where we replicated bimodal onset age and observed significantly greater odds of glandular fever\/infectious mononucleosis as a trigger in early onset cases (OR\u2009=\u20092.32, 95% CI [1.99\u20132.71], p\u2009=\u20092.4 \u00d7 10\u221224). Our findings suggest that incidence of ME\/CFS peaks in adolescence and in early middle-age and that early onset ME\/CFS is more common in those with affected relatives, more often triggered by infection, and associated with more severe disease.<\/jats:p>","DOI":"10.1093\/oxfimm\/iqag007","type":"journal-article","created":{"date-parts":[[2026,3,18]],"date-time":"2026-03-18T03:56:58Z","timestamp":1773806218000},"source":"Crossref","is-referenced-by-count":1,"title":["Incidence age is bimodal for myalgic encephalomyelitis\/chronic fatigue syndrome, with higher severity burden for early onset disease"],"prefix":"10.1093","volume":"7","author":[{"given":"Simon J","family":"McGrath","sequence":"first","affiliation":[{"name":"c\/o Action for ME, Unit 2.2 Streamline, 436-441 Paintworks , Bristol, BS4 3AS,","place":["United Kingdom"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8885-7065","authenticated-orcid":false,"given":"Charles B","family":"Hillier","sequence":"additional","affiliation":[{"name":"c\/o Action for ME, Unit 2.2 Streamline, 436-441 Paintworks , Bristol, BS4 3AS,","place":["United Kingdom"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Joshua J","family":"Dibble","sequence":"additional","affiliation":[{"name":"MRC Human Genetics Unit, Institute of Genetics and Cancer, University of Edinburgh , Edinburgh, Scotland, EH4 2XU,","place":["United Kingdom"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Trude","family":"Schei","sequence":"additional","affiliation":[{"name":"Norwegian ME Association , Nedre Slottsgate 4 M , 0157, Oslo,","place":["Norway"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6037-6849","authenticated-orcid":false,"given":"Arild","family":"Angelsen","sequence":"additional","affiliation":[{"name":"School of Economics and Business, Norwegian University of Life Sciences (NMBU) , PO Box 5003, 1432, \u00c5s,","place":["Norway"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0008-2248-2131","authenticated-orcid":false,"given":"Audrey A","family":"Ryback","sequence":"additional","affiliation":[{"name":"MRC Human Genetics Unit, Institute of Genetics and Cancer, University of Edinburgh , Edinburgh, Scotland, EH4 2XU,","place":["United Kingdom"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"286","published-online":{"date-parts":[[2026,3,17]]},"reference":[{"key":"2026041223433832500_iqag007-B1","doi-asserted-by":"crossref","first-page":"2129","DOI":"10.1001\/archinte.159.18.2129","article-title":"A community-based study of chronic fatigue syndrome","volume":"159","author":"Jason","year":"1999","journal-title":"Arch Intern Med"},{"key":"2026041223433832500_iqag007-B2","doi-asserted-by":"crossref","first-page":"1417","DOI":"10.1186\/s12889-025-22603-9","article-title":"Unequal access to diagnosis of myalgic encephalomyelitis 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