In their recent paper, Wolstenholme et al (Reference Wolstenholme, Fenn and Gray2002) demonstrated that changes in cognitive and functional status have independent and significant effects on the costs of care in dementia. We agree with the authors that models of costs based solely on measures of cognitive changes are inappropriate to describe variables influencing the costs of dementia. From 1994 to 1999 we conducted in Italy a longitudinal study on costs of Alzheimer's disease (the CoDem Study), based on information obtained every 6 months from a sample of 148 patients with Alzheimer's disease living at home (73.6% female, mean (s.d.) age 78 (7.8) years, mean (s.d.) Mini-Mental State Examination (MMSE) score at baseline 8.9 (8.3)), estimating direct and indirect costs of dementia (Reference Trabucchi, Ghisla, Bianchetti, Giacobini and BeckerTrabucchi et al, 1996). In a preliminary analysis after the first year of observation, using a logistic regression analysis, we found that greater annual costs for Alzheimer's disease are significantly associated more with disability than with cognitive decline (Reference Bianchetti, Frisoni and GhislaBianchetti et al, 1998). Following this line of investigation, we evaluated the modification of costs with the progression of the disease at the end of the 6-year longitudinal study with a Markov state transition model based on the comparison of costs for different states of cognitive and functional decline (measured using the MMSE and the Basic Activities of Daily Living (BADL) scale) (Reference Jönsson, Lindgren and WimoJönsson et al, 1999). In our study total costs (per year) for dementia care varied from [UNK]15 450 (£9972) for independent patients (BADL lost=0), to [UNK]21 463 (£13 853) for partially independent subjects (1-3 BADL lost) and [UNK]23 762 (£15 336) for totally dependent patients (4-6 BADL lost). Using the MMSE, the costs varied from [UNK]18 024 (£11 633) for patients with mild Alzheimer's disease (MMSE >20), to [UNK]19 665 (£12 692) for patients with moderate decline (MMSE 15-20) and [UNK]25 351 (£17 077) for patients with severe cognitive decline (MMSE 8-14) (Reference TrabucchiTrabucchi, 1999).

Our data, obtained in a sample of subjects with Alzheimer's disease living in a different social and cultural context, strengthen those obtained by Wolstenholme and colleagues, emphasising in particular the need to demonstrate an effect on functional status in the cost-effectiveness analysis of interventions in dementia.