Physical activity at age 11 years and chronic disabling fatigue at ages 13 and 16 years in a UK birth cohort, 2018, Crawley et al

Open access at http://adc.bmj.com/content/early/2018/01/30/archdischild-2017-314138 if you can stomach it.

Crawley continues her "chronic disabling fatigue" = ME fiction
"Here we use data from the Avon Longitudinal Study of Parents and Children (ALSPAC) to investigate whether levels and patterns of physical activity at age 11 years20 are associated with ‘chronic disabling fatigue’ (CDF, a proxy for clinically diagnosed CFS/ME) at ages 13 and 16 years."

 

Total and moderate-to-vigorous physical activity and sedentary time at age 11 years were measured by accelerometry over a 7-day period.

Surely not the same accelerometry that children found stigmatizing, so subjective reporting was the only possible recourse that researchers respecting children and adolescents wishes had at their disposal

 

As I've remarked before, a journal allowing the sentence 'CDF, a proxy for CFS/ME' through peer review is presumably one that would also publish a study on the effects of cough syrup on lung cancer in which the primary outcome is 'cough, a proxy for carcinoma'.

The bit that jumps out is was the conclusion's mention of reverse causation. On the face of it, that's obvious in any longitudunal study but also raises the question: did they exclude 11 year olds who already met, or were close to meeting, the criteria for CDF? Otherwise all one's shown is that kids who are ill at 13 may also have been ill at 11...

 

Respiration, a predictor of long-term mortality.

 

I've googled, but I can't find a definition of accelerometry that works in this context. What is it?

According to dictionary.com an accelerometer is "an instrument for measuring the acceleration of a moving or vibrating body".

 

What have they been doing to those poor children?

 

Activity tracker, such as a Fitbit or similar.

 

It's an actometer. The accelerometer in an actometer is used to help measure movement - steps, changes in position, etc.

 

Thanks, @Andy and @Valentijn

 

Actometers that were specified for use in 2007 PACE trial protocol for patients at baseline but considered an unnecessary encumbrance on recovered participants at the end of the trial.
Dutch FITNET did use ankle bracelet actometers but did not include data from them in the final published report.
A reasonable person may think actometers should have some warning attached when used in research, perhaps along the lines of this device could seriously damage your hypothesis.

 

The subtle definition change from previous paper now has a life of it' s own. Perhaps we should invent labels for other conditions to trivialise them too? Chronic disabling headache- brain tumour.....

 

Guys, epidemiological research like this often isn't perfect but is better to be done than not done, in terms of hypothesis generation, even with the dodgy criteria. The key is not to assume the conclusions are generalisable.

 

Out of interest, are there any other illnesses that are arbitrarily renamed ?

 

So as the authors say the definition at 16 years is more rigourous as it also requires the patients to report significant fatigue along with the parents' report.

 

Not important, but I don't understand the underlined bit.

 

They only excluded people whose fatigue had lasted 5 years or more. There was a 2nd category they included:

So people's fatigue at age 13 could have started before the age of 11 in which case it would not be surprising they might have been doing low activity levels.

When they just restricted the analyses to those whose disabling fatigue had lasted 3-5 months, this is what they found:

Significant results are found only when the 95% confidence intervals are both on the same side of one. When one is below 1 and the other is above 1, the result is not statistically significant.