Insomnia - treatment pathways, costs and quality of life

Table 3 Health care cost of those with insomnia versus non-insomniacs

Item	Base Case	Year of data	Notes
Per capita health care resource cost ($) of all ages New Zealand population (TP$)	3,568	2008	(1)
Personal medical services ($M)	15,313	2008	(2)
Population all ages (M)	4.292	2008	(3)
Proportion of New Zealand population suffering from insomnia (Ip)	0.13		(4)
% Increase in cost per capita of those with insomnia versus non-insomniacs	18.0%		(5)
Ratio of health resource cost of those with insomnia to non-insomniacs (R)	1.18		(5)
Mean health care resource cost ($) of non-insomniacs (Y)	3,486		(6)
Mean health care resource cost ($) of those with insomnia (X)	4,114		(6)
Increase in cost per capita those with insomnia versus non-insomniacs	628		(6)

Notes:
Data sources
(1) = (2) ÷ (3)
(2) Personal medical services: excludes expenditure on prevention and public health, administration and insurance premiums [41].
(3) Population: Total resident population[31]
(4) [8]
(5) [14, 17–20]
(6) Derivation of "Y" and "X" from "Ip" "R" and TP$
Unknown
X = Mean health care resource cost ($) of those with insomnia
Y = Mean health care resource cost ($) of non-insomniacs
Known (Statements S1, S2, S3)
(S1): Ip = Proportion of New Zealand population suffering from insomnia, [base case 0.13]
(S2): R = Ratio of health resource cost of those with insomnia to others, [base case 1.18]
(S3): TP$ = Mean health care resource cost of total all ages New Zealand population, [base case $3,568]
Solution
(S1) and (S3) may be used to derive equation (E1): TP$ = Ip × X + [(1 - Ip) × Y] (S2) may be written as equation (E2): × = R × Y
Substitute (E2) into (E1)
TP$ = [Ip × R × Y] + [(1 - Ip) × Y]
TP$ = Y × [(Ip × R) +1 - Ip)]
Solve for Y
Y = TP$/[(Ip × R) + 1 - Ip]
Using base case values as an example
Y = $3,568/[(0.13 × 1.18)+1-0.13] = $3,486
X = ($3,486 × 1.18) = $4,114
All calculations are based on unrounded data.

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