2.2. Parameters used in the model
The parameters used in the decision model are listed in Table 1 and discussed in detail in the subsequent sections. We defined a “high tHcy concentration” as . 13 mmol/L, as used by Pfeiffer et al [15]. The VITACOG trial showed that elderly people with mild cognitive impairment who had concentrations of tHcy above 13 mmol/L responded to B-vitamin treatment with a 53% reduction in the rate of whole brain atrophy [10], a 9-fold slowing of the rate of at- rophy of specific brain regions involved in Alzheimer’s dis- ease [11], and a measurable clinical improvement as assessed by the Clinical Dementia Rating score [12].