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

Table 15 Interpretation of regressions between total lost productivity (LP) and migraine-attributed impairment (maI) in all countries ordered by increasing population mean maI

Value item	Country
Value item	Pakistan	Nepal	India	Russia	China	Lithuania + Luxembourg	Ethiopia	Spain
Population mean maI¹ (arbitrary units)	10.8	14.2	15.1	17.2	19.7	20.1	21.2	22.2
Regression equation² (Y=)	0.05x + 7.2	0.01x + 1.9	0.07x + 0.6	0.02x + 1.9	0.15x + 3.4	0.06 + 1.4	0.03x + 2.1	0.13x + 2.8
Population-level LP³ (Y):
Y₁ where x = maI	7.74	2.04	1.66	2.24	6.36	2.60	2.74	5.69
Y₂ where x = 0.5*maI⁴	7.47	1.97	1.13	2.07	4.88	2.00	2.42	4.24
Y₂/Y₁	0.97	0.97	0.68	0.93	0.77	0.77	0.88	0.75
Recovery of LP for 50% reduction in maI (%)⁵	3	3	32	7	23	23	12	25
Pro rata recovery of LP per unit reduction in maI	0.06	0.06	0.64	0.14	0.46	0.46	0.24	0.50

¹From Table 1; ² from Table 13; ³ calculated from regression equation; ⁴ assuming intervention has achieved 50% reduction; ⁵ calculated as [1-(Y₂/Y₁)]*100; see text for further explanations

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