The total cost to implement each of the three salt substitution strategies by year of implementation is shown in Table 5. The cost of the subsidised strategy started at 13,678,227,816 ₫ (US$ 589,313) in year 1, increased to 30,539,726,723 ₫ (US$ 1,326,193) in year 2 and decreased to an ongoing cost of 21,808,968,902 ₫ (US$ 977,354) for years 6+. The cost of the regulatory strategy started at 12,186,495,637 ₫ (US$ 525,043) in year 1, increased to 17,311,069,141 ₫ (US$ 751,688) in year 2 and decreased to an ongoing cost of 12,949,953,247 ₫ (US$ 580,410) for years 6+.
Table 5
Total cost of each programme implementation phase (per year)
Phase | Voluntary | Subsidised | Regulatory |
Planning (Year 1) | 0 ₫ (US$ 0) | 13,678,227,816 ₫ (US$ 589,313) | 12,186,495,637 ₫ (US$ 525,043) |
Development (Year 2) | 0 ₫ (US$ 0) | 30,539,726,723 ₫ (US$ 1,326,193 | 17,311,069,141 ₫ (US$ 751,688) |
Partial implementation (Years 3–5) | 0 ₫ (US$ 0) | 24,336,782,722 ₫ (US$ 1,073,542) | 12,843,983,050 ₫ (US$ 566,570) |
Full implementation (Years 6+) | 0 ₫ (US$ 0) | 21,808,968,902 ₫ (US$ 977,354) | 12,949,953,247 ₫ (US$ 580,410) |
On a yearly basis, the total cost of the voluntary, subsidised and regulatory strategies was estimated to be 0 ₫ (US$ 0.00), 536 ₫ (US$ 0.02) and 37 ₫ (US$ 0.00) per capita, respectively. However, these costs were offset by healthcare savings due to reduced salt intake and reduced stoke and IHD events. Overall the yearly per capita savings across the three salt substitute scenarios was 49 ₫ (voluntary; US$ 0.00), 617 ₫ (subsidised; US$ 0.03) and 3,479 ₫ (regulatory; US$ 0.15) (Table 6). Extrapolated to a population level, the yearly cost savings would be between 4,775 m ₫ (US$ 205,764) for the voluntary strategy and 337,603 m ₫ (US$ 14,545,300) for the regulatory strategy.
Table 6
Costs accrued with each salt substitute strategy per capita per year
Parameter | No intervention | Voluntary | Subsidised | Regulatory |
Average salt substitute strategy costs per capita per year | 0 ₫ | 0 ₫ | 63 ₫ (US$ 0.00) | 37 ₫ (US$ 0.00) |
Average salt reformulation cost per capita per year | 0 ₫ | 0 ₫ | 473 ₫ (US$ 0.02) | 0 ₫ |
Average healthcare cost per capita per year | 15,050 ₫ (US$ 0.65) | 15,001 ₫ (US$ 0.65) | 13,896 ₫ (US$ 0.62) | 11,534 ₫ (US$ 0.50) |
Average total cost per capita per year | 15,050 ₫ (US$ 0.65) | 15,001 ₫ (US$ 0.65) | 14,433 ₫ (US$ 0.62) | 11,571 ₫ (US$ 0.50) |
Average total incremental cost per capita per year | | -49 ₫ (US$ 0.00) | -617 ₫ (US$ 0.03) | -3,479 ₫ (US$ 0.15) |
Total incremental savings per year* | | 4,775 m ₫ (US$ 205,764) | 59,873 m ₫ (US$ 2,579,547) | 337,603 m ₫ (US$ 14,545,300) |
*Assuming population of 97,040,334 |
Relative to no intervention, all three of the salt substitution strategies were found to result in less costs and more QALYs gained over a lifetime. Savings and health gains were driven by reductions in stroke and IHD events. Over the model lifetime (~ 70 years), the voluntary strategy avoided 32,595 and 22,830 stroke and IHD events, respectively. The subsidised strategy avoided 768,384 and 537,157 stroke and IHD events respectively, and finally, the regulatory strategy avoided 2,366,480 and 1,648,590 stroke and IHD events respectively (Table 7).
Table 7
Results of the salt substitute cost-effectiveness model
Strategy | Cost | Incremental Cost | Strokes avoided | IHD events avoided | QALYs gained | Incremental Effectiveness | ICER |
No intervention | 1,053,481 ₫ (US$ 45.39) | - | - | - | 13.33 | - | - |
Voluntary | 1,050,036 ₫ (US$ 45.24) | -3,445 ₫ (-US$ 0.15) | 32,595 | 22,830 | 13.34 | 0.009 | DOMINANT |
Subsidised | 1,010,292 ₫ (US$ 43.53) | -43,189 ₫ (-US$ 1.86) | 768,384 | 537,157 | 13.35 | 0.022 | DOMINANT |
Regulatory | 809,951 ₫ (US$ 34.90) | -243,530 ₫ (-US$ 10.49) | 236,6480 | 1,648,590 | 13.41 | 0.074 | DOMINANT |
Abbreviations: ICER, incremental cost-effectiveness ratio; IHD, ischaemic heart disease; QALY, quality adjusted life year |
While all three strategies reduced average government costs, the voluntary salt substitution strategy provided the smallest average cost reduction (3,445 ₫; US$ 0.15) and effectiveness benefit (0.009 incremental QALYs gained), as it provided the lowest reduction in dietary sodium intake and thus the lowest reduction in IHD or stroke risk. The subsidised strategy provided an average cost-saving of 43,189₫ (US$ 1.86) and resulted in an average incremental QALY gain of 0.022. The regulatory strategy provided the highest cost savings (243,530 ₫; US$ 10.49) and incremental QALYs gained (0.074) (Table 7).
As shown in Fig. 1, savings from reduced healthcare offset implementation costs for all three salt substitution strategies. The savings and effectiveness increase when moving from the voluntary strategy to the subsidised strategy to the regulatory strategy due to the increasing population coverage of the reformulated products.
Sensitivity and threshold analyses
The results of the sensitivity analysis for the voluntary, subsidised and regulatory strategies compared to no intervention are presented in detail in the Supplementary Material (see Supplementary Tables 5–7). Overall, all strategies proved to be robust to all parameter changes, with all three salt substitution strategies remaining dominant (less costly and more effective) for all scenarios with the exception of removing all Government healthcare costs.
Threshold analysis results are presented in Table 8. For the voluntary strategy the average daily salt reduction required for costs to equal savings was < 0.01 g at all time horizons. Due to the larger government investment in the subsidised strategy, the average salt reduction for costs to equal savings was 2.17 g, 0.27 g and 0.15 g at 20 years, 40 years and over a lifetime respectively (the reduction required at 10 years exceed the average daily intake). For the regulatory strategy, the average salt reduction for costs to equal savings was 1.44 g, 0.18 g, 0.05 g and 0.04 g at 10 years, 20 years, 40 years and over a lifetime respectively.
Table 8
Average daily salt reduction required for strategy costs to equal savings
Time horizon | Voluntary | Subsidised | Regulatory |
10-years | < 0.01 g | NA | 1.44 g |
20-years | < 0.01 g | 2.17 g | 0.18 g |
40-years | < 0.01 g | 0.27 g | 0.05 g |
Lifetime | 0 g | 0.15 g | 0.04 g |
NA: The salt reduction required for costs to equal savings was greater than the average daily intake. |
Validation
A comparison of the current model with previous publications including Ha 2011 [13], Webb 2017 [26] and Cobiac 2010 [18] is provided in the Supplementary Material (see Supplementary Table 8).