Why is it so difficult to evaluate nursing interventions in dementia?

Two recent health technology assessment (HTA) reports published in Germany focused on non-pharmacological interventions for patients with dementia. One of the major results was the poor methodological quality of the studies in this field. This paper concisely presents the main quantitative and qualitative findings of the HTA report published by the German Agency for HTA at the Institute of Medical Information and Documentation (dahta@DIMDI), followed by a detailed discussion of the major methodological problems observed for the inclusion criteria, interventions, the setting, number of patients included, duration of observation, comparators, clinical endpoints, health economics, and, most obvious, the impossibility of blinding and eliminating placebo effects for future clinical studies. We conclude with several suggestions addressing these challenges for future research in this field.