By David Tuller, DrPH
Leonard Jason, a professor of psychology at DePaul University in Chicago, is a recognized expert in research on the prevalence of and case definitions for the illness (or cluster of illnesses) variously referred to as myalgic encephalomyelitis, chronic fatigue syndrome, ME/CFS, CFS/ME and other names. I posted an interview with him on case definition a couple of years ago.
Professor Jason recently co-led a study called “The prevalence of pediatric myalgic encephalomyelitis/chronic fatigue syndrome in a community-based sample.” The study–the most rigorous of its kind–was published last month by the journal Child & Youth Care Forum. I asked him why he thought the study was needed. Here’s what he said:
I did the study because most prior pediatric prevalence studies of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) have been based upon data from tertiary care centers, a process known for systematic biases such as excluding youth of lower socioeconomic status and those less likely to have access to health care. In addition, most pediatric ME/CFS epidemiologic studies have not included a thorough medical and psychiatric examination.
The purpose of this study was to determine the prevalence of pediatric ME/CFS from an ethnically and sociodemographically diverse community-based random sample. The results are clear cut–using physicians or health care workers to identify youth with ME/CFS will result in under-diagnosis of this illness. In other words, many youth with the illness have not been previously diagnosed with ME/CFS. These findings point to the need for better ways to identify and diagnose youth with this illness, and ultimately to find ways to treat those with this illness, most of which have not been diagonosed.
Leonard Jason research finds that many young people have ME/CFS (by Simon McGrath)
How do you find out how common an illness is when it is hard to diagnose, most doctors know little about it and many of them dismiss it as trivial? ME/CFS just is such an illness. Asking doctors to report the number of people they have diagnosed is likely to miss many real cases and studies using this method concluded that ME/CFS is rare. A better approach, used by a new study, is to screen large numbers of people in the community to find those that might have the illness, then give those people a thorough medical workup to establish who actually has it.
Professor Leonard Jason and Dr Ben Katz led the new study and they estimated that 0.75% of young people aged 5 to 17 have ME/CFS, roughly one in every 130. The estimate isn€™t exact, and the study authors say the figure could be as low as 0.54% and as high as 0.96%. Even using the low estimate would mean 290,000 in the US have the illness, along with 55,000 in the UK. Which suggests that ME/CFS is far from rare and is ruining a lot of young lives.
The 0.75% estimate is significantly higher than most generally-accepted estimates for adults. The CDC estimated 0.24% of adults had ME/CFS and Jason estimated 0.42%, both using a community screening approach similar to that used in the new study. ME/CFS affects a lot of adults but it appears to be an even more common problem for children. “The most important thing for children is to be accepted by their peers and if you don€™t have the energy to socialize and do things with them and develop those friendships, that is a real obstacle,” Professor Jason told the Chicago Tribune
Worryingly, the study also found that only 1 in 20 of the young people they diagnosed with ME/CFS already had a diagnosis. Though perhaps this is not so surprising, given that other studies in the US have found that only 10% to 15% of adults who have ME/CFS actually have a diagnosis.
ME/CFS is more common in older and non-white under 18s
This study collected data from 10,000 young people with diverse ethnic backgrounds and was able to estimate how common ME/CFS is in people with different ethnicity. It found that the illness was significantly more common among African American (1.1% prevalence) and Hispanic (1.3%) young people than among whites (0.63%).
ME/CFS also becomes increasingly common as children move into adolescence, as the graph below shows.
The authors suggested the changes with age could be due to the hormonal and psychological changes of adolescence. It could, they say, also be due to children being exposed to more environmental and biological factors as they get older. One factor in the increase is likely to be glandular fever (infectious mononucleosis), which leads to ME/CFS for about one person in ten. Glandular fever becomes more common in adolescence because the virus that triggers it is spread by kissing.
How the study worked
The study had two phases. In the community screening phase, the study used trained volunteers to call 137,000 telephone numbers in greater Chicago. These calls identified 23,000 households with children between the ages of five and 17. Just under a quarter of these households, 5,600 (24%), agreed to take part in the screening questionnaire, which collected information on 10,000 children.
The screen of 10,000 children identified 295 who might have ME/CFS, because they had fatigue or school/learning/memory problems, significantly reduced ability to function, and particular symptoms. They also didn€™t have any illnesses such as multiple sclerosis that would rule out a diagnosis of ME/CFS.
In the second, diagnostic phase, researchers invited all 295 children and teenagers to attend a clinic in Chicago for a full medical evaluation. This involved questionnaires screening for psychological problems, measuring ME/CFS symptoms and assessing fatigue, as well as blood tests and a physical examination by Dr Ben Katz, one of the leading US children€™s physicians specializing in ME/CFS.
A team of physicians made the final decision about who had ME/CFS after reviewing each patient€™s information. To get a diagnosis, every patient also had to meet three case definitions (for the geeks: IOM, Fukuda and Canadian consensus criteria).
The researchers assessed 165 and concluded that 42 of them had ME/CFS. Only two of the 42 already had a diagnosis of the illness. The 42 cases computes to an ME/CFS prevalence of 0.75%.
Low response to telephone survey introduces uncertainty
A limitation of the study, mentioned by the authors in their paper, is the low response rate to the telephone screen. This is a general trend: people are increasingly unwilling to take part in telephone surveys. It is possible that the relatively small proportion of people who did take part are not a representative sample, and if that were the case ï¿¼it would affect the accuracy of the prevalence estimate.
The calculation of 0.75% prevalence assumes that those who do respond to studies like this are much the same as the ones who don€™t. That assumption might not hold true when most people don€™t respond. As the authors say in their paper, this has become a real problem for telephone surveys, including their own.
Back in the 1990s, Jason ran an adult prevalence study with a similar design. Two-thirds of the households they contacted not only answered the phone but went on to complete the screening questionnaire. In this new study, of the minority who answered the phone (and who had children the right age) only a quarter were willing to complete the screening questionnaire.
Jason and colleagues pointed out that the young people they diagnosed had family incomes significantly higher than average for Chicago. Rather than a higher family income makes a child more likely to develop ME/CFS, the authors believe that such families might be more willing to participate in the study or to be more able to take the time to attend the clinic for the assessment.
There could, some patients suggest, be a similar but bigger problem where families who have a child with fatigue are more willing to take part in the screening phone call than families who don€™t. This would place a disproportionate number of fatigued people in the study, which would produce a prevalence figure for ME/CFS that is too high. But we don€™t know if this has happened to a significant extent.
A strong study design
Despite the problems of the low response rate, this NIH funded research uses a strong design and is the best study yet on prevalence in young people.
In fact, the findings of the new study are backed up by an earlier study run by Professor Esther Crawley. Her team used a slightly different approach, screening all children who had missed more than 20% of school in a six week period, and found a prevalence of 1%. Even allowing for differences in method between the two studies, the results are pretty similar. [Virology Blog: Of course, this is the study in which Professor Crawley interviewed many dozens of minors and their family members without ethical review, based on the false claim that the study constituted “service evaluation” and was therefore exempt from such oversight.]
The relatively high rate of ME/CFS in young people found by the study equates to hundreds of thousands of people living with the illness. The vast majority of them probably have no diagnosis. ME/CFS is a serious condition, is the biggest cause of long-term school absence and takes a huge toll on young lives. We know next to nothing about the causes of ME/CFS and there are no effective treatments. Only serious levels of investment in research can put this right.