We thank you for the opportunity to respond to the letter written by Dr. Lourenço and Dr. Paradela, our colleagues from Rio de Janeiro. We understand scientific progress relies on lively debate and exchange of experiences; therefore, we also thank our colleagues for the opportunity to reflect upon our previous findings.
We identified three major issues in their letter and we respond to them in the items below.
1. CDR = 0.5 as Alzheimer's disease. It is well known that the Clinical Dementia Rating (CDR) was developed to stage cognitive impairment and that CDR = 0.5 may represent early stage AD or mild cognitive impairment (MCI). In our study, the 37 subjects with CDR = 0.5 presented with significant functional impairment and, therefore, were classified as early-stage AD (Mayeux, Reference Mayeux2010).
2. We agree with our colleagues that the validation of cognitive instruments developed under different cultural backgrounds is a complex process which requires several steps. Nonetheless, when we initiated data collection we used the only available version of the CAMCOG adapted and validated by Bottino et al. (Reference Bottino, Stoppe, Scalco, Ferreira, Hototian and Scalco2001), who presented data suggesting appropriate psychometric characteristics for the battery. Several other Brazilian studies have used this version (Nunes et al., Reference Nunes, Diniz and Radanovic2008).
3. We also agree with our colleagues that “participation in social, cultural and labor activities are fundamental experiences which determine the overall capacity of the brain.” One of the interesting points of our paper is showing that the CAMCOG depends upon aspects other than education. Our sample was recruited from a private clinic and most likely has a better socioeconomic profile than samples from public services. Our sample also had a monthly income of around US$ 882 (equivalent to three minimum wages in Brazil), which does not equate to saying that our population was not poor. In Brazil, because of insufficient public health resources, people from various economic layers reach private services for better quality. In addition, Jundiaí is a city in São Paulo with high human development index. We understand our findings suggest that the impact of education on cognition may be mediated by cultural and socioeconomic factors which may come into play after formal schooling takes place. For further information on this topic, please refer to other papers from our group (Aprahamian et al., Reference Aprahamian, Martinelli, Neri and Yassuda2010; Reference Aprahamian, Martinelli, Cecato and Yassuda2011)
In summing up, the authors do not agree that the presented findings were affected by “sample and classification bias.”
Conflict of interest
None.
