Cognitive impairment at older ages among 8000 men and women living in Mexico City: a cross-sectional analyses of a prospective study by González-Carballo, C, Kuri-Morales, P, Chiquete, E, Rojas-Russell, M, Santacruz-Benitez, R, Ramirez-Reyes, R, Garcilazo-Ávila, A, Berumen, J, Trichia, E, Friedrichs, LG, Orellana, P, Ochoa-Rosales, C, O’Donovan, G, Emberson, JR, Tapia-Conyer, R, Aguilar-Ramirez, D, Alegre-Díaz, J