The relationship between headache-attributed disability and lost productivity: 1. A review of the literature

DOI: https://doi.org/10.1186/s10194- 021- 01264- 0

Abstract-Summary Headache disorders are disabling and have a significant impact on productivity.

We followed PRISMA guidelines in specifying search terms and syntax and in

article selection.

We used the term “disability” in the search, accepting any meaning that authors

attached to it, but this proved problematic.

In article selection, we included only those that purported to measure disability

as so defined and lost productivity.

We included further articles identified from review of the bibliographies of

selected articles.

The literature search found 598 studies, of which 21 warranted further review. Ten applied incompatible definitions of disability and/or lost productivity. Four reported lost productivity but not disability. Eight studies reported and measured both but did not assess the association

between them or provide the means of doing so.

The literature is silent on the relationship between headache-attributed disability

and lost productivity.

Extended: We followed PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines in specifying search terms and syntax and in article selection.

In article selection, therefore, we defined disability restrictively, only in this

sense, notwithstanding our reservations about it expressed earlier.

Eight studies reported and measured both as we defined them, but did not assess association between the two or provide the means of doing so [204, 263, 264, 266, 268, 372–407].

Background The Global Burden of Disease study (GBD) in its multiple iterations shows that three headache disorders—migraine, tension-type headache (TTH) and medication- overuse headache (MOH), which is a sequela of migraine or TTH—are major con- tributors to public ill health [8–368].

In GBD2019, the most recent to be analysed, headache disorders were estimated to be responsible for 46.6 million years lived with disability (YLDs) globally (5.4% of all YLDs), with an age-standardized rate of 602.5 YLDs/100,000 person-years [368, 369].

For episodic headache disorders such as migraine and TTH, two essential health states are recognised: ictal (during attacks) and interictal (between attacks) [50, 408]. The ill health associated with headache disorders, and the disability that is its

consequence, inevitably lead to lost productivity [50].

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Economics

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The Eurolight project, a survey conducted in ten European countries, estimated societal losses attributable to all headache disorders (direct and indirect costs) at well over €100 billion per year, with more than 90% attributable to lost productiv- ity [409].

Methods We conducted a systematic review of the English-language literature evaluating the relationship between headache-attributed ill health (expressed as symptom burden or disability) and lost productivity.

We followed PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines in specifying search terms and syntax and in article selection.

In the initial search, lost productivity was defined to include days of absenteeism from or < 50% productivity in paid or household work (the MIDAS construct [237]), estimated either over the preceding 3 months or in association with headache yes- terday [50].

We took the term disability to have any meaning attached to it in the literature,

but in the subsequent selection of articles this was problematic.

We included studies that purported to measure disability so defined and lost pro-

ductivity defined only as above.

All full-text articles found in this process were scrutinised for evidence or com-

ment regarding the relationship between disability and lost productivity.

Results Ten applied different definitions of headache-attributed disability and/or lost pro- ductivity, incompatible with ours [197, 377, 410–417].

Four measured lost productivity according to our definition, but did not report

disability [4, 118, 131, 418].

Eight studies reported and measured both as we defined them, but did not assess association between the two or provide the means of doing so [204, 263, 264, 266, 268, 372–407].

The literature was entirely silent with regard to the relationship between

headache- attributed disability and lost productivity.

Discussion Our systematic review of the literature, with the enquiry framed broadly, found not just that it said nothing on the relationship between headache-attributed disability and lost productivity but that this issue of substantial health-economic importance had not even been addressed [90, 118, 131, 408–419].

There is a wealth of empirical evidence of the lost productivity burden of head- ache and its economic consequences (e.g., [118, 131, 204, 264, 266, 270, 405, 406, 409–419]), to which indirect costs (essentially from lost productivity) are far more contributory than direct health-care costs [409].

If pain intensity were introduced in its place (pTIS * mean intensity) to generate what might be considered a measure of symptom burden—impairment rather than “disability”—the result would arguably be a more nuanced measure of health loss,

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which might relate to lost productivity more closely and offer a better way forward in future studies.

Some population studies have found that lost productivity due to headache (in percentage time units) exceeded percentage disability estimated as pTIS * DW [263, 266].

Conclusions A careful search of the English-language literature found nothing on the relation- ship between headache-attributed disability and lost productivity. A prerequisite is to clarify what is meant by “disability”.

Acknowledgement A machine generated summary based on the work of Kothari, Simple Futarmal; Jensen, Rigmor Hølland; Steiner, Timothy J. 2021  in The Journal of Headache and Pain.

Migraine day frequency in migraine prevention: longitudinal modelling approaches