Dimmock, Mirin & Jason: Estimating disease-burden in the US

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Yesterday, Mary Dimmock, Arthur Mirin and Leonard Jason published a hallmark study in disease burden in myalgic encephalomyelitis.

Why is funding so low?

Funding for ME/CFS is arguably the lowest per patient for any major disease in the United States, averaging to about $5 per patient per year.  Compare this to multiple sclerosis, an illness with many similarities to ME, but which receives over $200 per patient per year.

As Dimmock and colleagues note, however, disease burden in comparison to government spending is not a straight line.  The reasons a disease might be underfunded in comparison to others are complex and varied, and include the increases of funding that are the result of active political and activist campaigns, and decreases of funding where the public – and government – has the tendency to ‘blame the victim’.  COPD, for example, often the result of smoking, is underfunded in comparison to illnesses with similar disease burdens.  Therefore, an illness like ME/CFS may receive less government funding due to the perception that patients have got themselves into this mess – through action or inaction, or through personality or habits they ought to have taken better care to change.

There have been reports of stigma towards ME/CFS patients, researchers, and research, and more than one report of researchers’ studies being rejected because “ME/CFS isn’t real” or “ME/CFS is psychosomatic” or for poorly-articulated reasons that demonstrate a willingness to reject biomedical research proposals on ME out of hand.  “It is unconscionable that a disease that can cause this magnitude of disease burden has been neglected, trivialized, and mistreated for so long,” said Dimmock.

Using the DALY to measure disability

The World Health Organization (WHO) uses the Disability Adjusted Life Year (DALY) in order to measure disease burden.  This figure takes into account both years of disability and mortality, but also takes into account premature death and the debility of patients.  Rather than a fixed figure, the DALY changes as clinician and research knowledge deepens, and more treatments become available that affect quality of life.  For example, the disease burden of AIDS patients decreased by 61% between 1990 and 2010, according to Murray and colleagues in a study published in 2013.

The DALY is calculated by adding the years lost to disability to the years lost due to early death.

Calculating disease burden using DALY
DALY = YLD + YLL  = (P)(DW) + (N)(L)

Disability Adjusted Life Year =
= Years Lost Due to Disability + Years Lost Due to Death
= (Prevalence)(Disability Weight) + (Deaths per year)(Average loss in life expectancy per death)

The years lost due to disability (YLD) is calculated by utilizing prevalence figures (the number of patients in any given year), and the disability ‘weight’, a figure from zero to one that estimates what fraction of a patient’s time is swallowed by the disability.  The years lost due to early death (YLL) takes into account the number of deaths in any given year and the average loss of life expectancy for those deaths.  Perhaps needless to say, the DALY for ME/CFS is quite high in comparison to many other chronic and acute illnesses.

Disability weight

While there are other papers that have examined quality of life and disease burden using other measures, none have yet examined the DALY for ME/CFS patients.

If you’re with me so far, it becomes swiftly clear that disease burden can be calculated according to the wishes of the researchers; and it would be very tempting for Dimmock and colleagues to have chosen the highest prevalence figures available to slant the data to their benefit.

However, the researchers chose one of the lowest generally-accepted prevalence figures for ME/CFS – the 0.42% that would place the number of sufferers in the US at 836,000 when the study was first published, and almost exactly 1 million as of a 2013 census.  Since it’s generally accepted that children suffer from the illness at a lower rate, Dimmock and colleagues used the prevalence figures from Prevalence of Pediatric Chronic Fatigue Syndrome in a Community-Based Sample to indicate the different prevalence in children and adolescents.

In order to examine disability weight, Dimmock and colleagues referred to the oft-cited figure that approximately 25% of individuals with ME/CFS are housebound or bedbound.  By taking into account the CDC’s estimate, the IOM Report, and patient surveys, the group arrived at the figure of 27% of patients housebound or bedbound.  Utilizing this method, they found that the disability weight for ME/CFS was 0.4748.

They also used a second method for determining disability weight: 1 – Quality of Life (QOL) using the EQ-5D.  Utilizing this alternate method, they found that the disability weight was 0.44 – similar but not identical to the figure above.

These findings agree with the disability weights of illnesses that arguably have similar symptoms to ME/CFS; moderate and severe encephalopathy have a disability weight of 0.410 and 0.447, respectively; moderate multiple sclerosis has a disability weight of 0.469; and severe motor and cognitive impairment has a disability weight of 0.494, according to one large, population-based study.

Dimmock and colleagues averaged the result from the two methods to arrive at a disability weight of 0.46.

Years of life lost and number of deaths per year present unique challenges

However, predicting years of life lost and number of deaths per year presented a significant challenge.  There are few longitudinal studies on ME/CFS and mortality, and the fact that patients die of related illnesses or causes rather than ME/CFS itself is a confounding factor.  In the past, associations have been drawn between cardiovascular disease, cancer, and suicide.  Moreover, the deaths due to these conditions were, on average, at a younger age in ME patients than in controls.

In order to calculate the deaths statistically due to ME — and not to cancer, for example, in and of itself — Dimmock and colleagues compared the death rate in these illnesses in the population at large in comparison to the population of ME patients and found the difference.  Then, the researchers multiplied this difference by their ME prevalence figures to get the number of patient deaths arguably due to ME.

The 2006 Jason study was used to estimate premature years of death in lives lost due to cancer and ME, cardiovascular disease and ME, and suicide in ME patients.

How much should ME/CFS receive in funding per year?

While it may seem abhorrent in one way to quantify and compare suffering, it’s a necessity to determine whether or not the amount of funding allocated to ME/CFS research, treatment, and oversight is fair and reasonable.

The final DALY for ME patients was 0.714M or 714,000.  In comparison to other illnesses, this projects that the funding for ME research should be equivalent to $188,000,000/year, or $188 per patient per year.  That would be more than 25 times the funding allocated for research in the last calendar year in the US.

disease-burden-vs-funding
Journal of Medicine and Therapeutics, Dimmock et al, 2017
Limitations

There are limitations to every study, and by definition many of the epidemiological studies on ME/CFS have been small.  Estimates of prevalence shift depending on the diagnostic criteria, and there is an especial paucity of data regarding prevalence in children and adolescents.

Dimmock and colleagues note in the paper that, in the US, the diagnostic code for “chronic fatigue syndrome” and “chronic fatigue” as a symptom are identical, further muddying the waters.  Further research on a greater number of patients is necessary in order to further solidify disease burden estimates in ME.

However, even presuming Dimmock and her colleagues’ figures are off slightly in one direction or another does not explain a disease funded at between 3 and 4% of its disease burden in comparison to other illnesses.  “To address the poor state of research, HHS and other funding agencies must provide a fair share of funding and strategic commitment to ensure that the needed studies are done,” Dimmock said.
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1 thought on “Dimmock, Mirin & Jason: Estimating disease-burden in the US”

  1. The gross federal discrimination against M.E. must end in 2017, with RFAs and rampling up R&D funding toward a fairer $200 M per year. Anyone in congress, HHS, CDC should contribute to ending this discrimination, or be replaced. ME/CFS is over an order of magnitude underfunded, sentencing 1 million in US, often to life imprisoned with M.E., for doing nothing wrong, and with little chance of being freed of this disease until more R&D funded for effective diagnostics, treatments, and cures.

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