This study examines the relationship between neuropathological features of Alzheimer's disease and dementia in individuals aged 69 to 103 years. The research involved 456 brains donated to the Medical Research Council Cognitive Function and Ageing Study (CFAS). Neuropathological features, including Alzheimer's disease pathology, cerebral atrophy, and cerebrovascular disease, were assessed. Logistic regression was used to estimate the effect of age on the relationship between these features and dementia. The study found that the association between Alzheimer's-type pathological changes and dementia was stronger in younger old persons than in older old persons. The prevalence of moderate and severe Alzheimer's-type pathological changes decreased with increasing age, while the association between cerebral atrophy and dementia remained strong across all age groups. This suggests that cerebral atrophy is a more consistent marker of dementia in older individuals. The study also found that the association between neocortical neuritic plaques and dementia was strong at 75 years of age but reduced at 95 years of age. Similarly, the association between other Alzheimer's-related pathological features and dementia was attenuated with age. In contrast, cerebral atrophy remained strongly associated with dementia at both 75 and 95 years of age. The study highlights the importance of considering age when assessing the impact of interventions on dementia. It also suggests that the neuropathological features of dementia may change with age, and that the relationship between these features and dementia may be different in older individuals. The findings indicate that cerebral atrophy is a more reliable marker of dementia in older individuals, and that the association between Alzheimer's-type pathological features and dementia may be less strong in older individuals. The study also suggests that the neuropathological features of dementia may converge in older individuals, and that the relationship between these features and dementia may be different in older individuals. The study concludes that age must be taken into account when assessing the likely effect of interventions against dementia on the population.This study examines the relationship between neuropathological features of Alzheimer's disease and dementia in individuals aged 69 to 103 years. The research involved 456 brains donated to the Medical Research Council Cognitive Function and Ageing Study (CFAS). Neuropathological features, including Alzheimer's disease pathology, cerebral atrophy, and cerebrovascular disease, were assessed. Logistic regression was used to estimate the effect of age on the relationship between these features and dementia. The study found that the association between Alzheimer's-type pathological changes and dementia was stronger in younger old persons than in older old persons. The prevalence of moderate and severe Alzheimer's-type pathological changes decreased with increasing age, while the association between cerebral atrophy and dementia remained strong across all age groups. This suggests that cerebral atrophy is a more consistent marker of dementia in older individuals. The study also found that the association between neocortical neuritic plaques and dementia was strong at 75 years of age but reduced at 95 years of age. Similarly, the association between other Alzheimer's-related pathological features and dementia was attenuated with age. In contrast, cerebral atrophy remained strongly associated with dementia at both 75 and 95 years of age. The study highlights the importance of considering age when assessing the impact of interventions on dementia. It also suggests that the neuropathological features of dementia may change with age, and that the relationship between these features and dementia may be different in older individuals. The findings indicate that cerebral atrophy is a more reliable marker of dementia in older individuals, and that the association between Alzheimer's-type pathological features and dementia may be less strong in older individuals. The study also suggests that the neuropathological features of dementia may converge in older individuals, and that the relationship between these features and dementia may be different in older individuals. The study concludes that age must be taken into account when assessing the likely effect of interventions against dementia on the population.