# 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)
1. Notes:
2. Data sources
3. (1) = (2) ÷ (3)
4. (2) Personal medical services: excludes expenditure on prevention and public health, administration and insurance premiums [41].
5. (3) Population: Total resident population[31]
6. (4) [8]
7. (5) [14, 1720]
8. (6) Derivation of "Y" and "X" from "Ip" "R" and TP\$
9. Unknown
10. X = Mean health care resource cost (\$) of those with insomnia
11. Y = Mean health care resource cost (\$) of non-insomniacs
12. Known (Statements S1, S2, S3)
13. (S1): Ip = Proportion of New Zealand population suffering from insomnia, [base case 0.13]
14. (S2): R = Ratio of health resource cost of those with insomnia to others, [base case 1.18]
15. (S3): TP\$ = Mean health care resource cost of total all ages New Zealand population, [base case \$3,568]
16. Solution
17. (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
18. Substitute (E2) into (E1)
19. TP\$ = [Ip × R × Y] + [(1 - Ip) × Y]
20. TP\$ = Y × [(Ip × R) +1 - Ip)]
21. Solve for Y
22. Y = TP\$/[(Ip × R) + 1 - Ip]
23. Using base case values as an example
24. Y = \$3,568/[(0.13 × 1.18)+1-0.13] = \$3,486
25. X = (\$3,486 × 1.18) = \$4,114
26. All calculations are based on unrounded data.