An open-access free download of the research paper upon which today's news in based:
Archana Singh-Manoux, Mika Kivimaki, M Maria Glymour, Alexis Elbaz, Claudine Berr, Klaus P Ebmeier, Jane E Ferrie, &
Aline Dugravot (2012). Timing of onset of cognitive decline: results from Whitehall II prospective cohort study. British Medical Journal.