The relationship between headache-attributed disability and lost productivity: 2. Empirical evidence from population-based studies in nine disparate countries

DOI: https://doi.org/10.1186/s10194- 021- 01362- z

Abstract-Summary Headache disorders are disabling, with major consequences for productivity, yet the literature is silent on the relationship between headache-attributed disability and lost productivity, often erroneously regarding the two as synonymous.

We evaluated the relationship empirically, having earlier found that investment in structured headache services would be cost saving, not merely cost-effective, if reductions in headache-attributed disability led to > 20% pro rata recovery of lost productivity.

We assessed relationships in migraine and probable medication-overuse head-

ache (pMOH), the most disabling common headache disorders.

Disability, in the sense used by the Global Burden of Disease study, was mea-

sured as the product of pTIS and disability weight for the ictal state.

Lost productivity was measured as lost days (absence or  <  50% productivity) from paid work and corresponding losses from household work over the preceding 3 months.

For migraine, in a linear model, we found positive associations with lost paid worktime, significant (p < 0.05) in many countries and highly significant (p < 0.001) in some despite low values of R2 (0–0.16) due to high variance.

With lost household worktime and total lost productivity (paid + household), associations were highly significant in almost all countries, although still with low R2 (0.04–0.22).

Applying the regression equations for each country to the population mean migraine-attributed disability, we found pro rata recoveries of lost productivity in the range 16–56% (> 20% in all countries but Pakistan).

Relief of disability through effective treatment of migraine is expected, in most countries, to recover > 20% pro rata of lost productivity, above the threshold for investment in structured headache services to be cost saving.

Extended: Headache disorders are the cause of disabling ill health, awareness of

which has increased dramatically over the last decade [8, 31, 32, 34, 44, 47–369].

Relief of disability through effective treatment of migraine can be expected, in most countries, to recover, pro rata, > 20% of lost productivity, with country income level not a factor.

This is something for future studies: the data exist.

Background In an earlier paper, we searched the literature for evidence of the relationship between headache-attributed disability and lost productivity, recognising the impor- tance of this in the contexts of health care and policy [370].

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The crucial question was, and still is: “To what extent might alleviation of the symptom burdens of headache disorders—the principal cause of disability—be expected to reduce the lost-productivity burdens?”

Our aim here, therefore, was to evaluate the relationship between headache- attributed disability on the one hand and lost productivity on the other using empiri- cal data.

These data included symptom burden, allowing calculation of impairment, dis- ability (in the sense used within the Global Burden of Disease (GBD) studies [8, 31, 32, 34, 44, 50, 94–368, 370]), and lost productive time from paid work and house- hold chores.

Methods We defined headache-attributed disability as in the Global Burden of Disease (GBD) studies, expressed at population level in years lived with (or lost to) disability (YLDs) [8, 31, 32, 34, 44, 50, 94–368, 370].

We defined headache-attributed lost productivity in terms of absenteeism from or reduced productivity in paid work and corresponding losses in household work, ignoring, again for simplicity, the economically less important detriment to social participation.

Symptom enquiry relevant to estimation of disability (as defined) included head-

ache frequency (days/month) and usual attack duration (minutes, hours or days).

We calculated time in ictal state (TIS) at individual level as the product of head- ache frequency (F) and average duration converted into days (D), and expressed this as a percentage of total days (pTIS).

We assessed associations between these: headache-attributed disability or headache- attributed impairment as independent variables and lost productivity as dependent variable for each country and each headache type.

Results Evident in all, but more in some countries than in others, are numerous data points indicating high reported lost productivity despite low estimated disability.

Disability values are the same in each, with a possible range of 0–22% based on DW = 0.441 [371] since maximum pTIS was 50% (cases of headache on ≥15 days/ month were excluded).

The degrees of scatter indicate complexity and involvement of other factors in

the relationships.

With maximum pTIS = 100%, the possible range for disability was also 0–22%,

based on DW = 0.217 [371].

Numbers were relatively low, but the degrees of scatter, particularly in Pakistan with negative β, again indicate complexity and involvement of other factors in the relationships.

Discussion It was reported in one of the population studies that lost productivity due to migraine exceeded disability expected from time spent with headache [263], suggesting that the disabling effect of migraine outlasted headache.

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Interictal burden, on the other hand, which was ignored in our analyses (and is ignored in the GBD studies), would not be factored into disability estimates based on pTIS, but neither would we expect it to have an effect on lost productivity.

We should note, however, that for both disorders the relationship between dis- ability and lost productivity is complicated and weakened by a welter of interfer- ing external factors, with high variance reflected at population level in low values of R2.

LTB studies have introduced enquiry into headache yesterday [50] to obviate recall error in assessments of both disability and lost productivity, but the numbers, for now, remain small (1-day prevalence of migraine is low).

Conclusion Relief of disability through effective treatment of migraine can be expected, in most countries, to recover, pro rata, > 20% of lost productivity, with country income level not a factor.

While any recovery will offset costs of care provision, our earlier analyses indi- cate that investment in structured headache services will be cost saving, not merely cost-effective, if proportionate recovery of lost productivity is above this level.

It is likely that a stronger relationship exists at individual level, where many of

the extraneous factors are constant.

Introducing headache intensity into our analyses, attempting to reflect impair- ment and a more nuanced assessment of individual health loss, was not useful for reasons explained.

Acknowledgement A machine generated summary based on the work of Thomas, Hallie; Kothari, Simple Futarmal; Husøy, Andreas; Jensen, Rigmor Højland; Katsarava, Zaza; Tinelli, Michela; Steiner, Timothy J. 2021 in The Journal of Headache and Pain.

The Humanistic and Economic Burden of Migraine in Europe: A Cross-Sectional Survey in Five Countries