Of course downloads are increased by OA before citations. Downloads are immediate. Writing a paper, citating a published paper in it and publishing the citing paper take time, and that is reflected in the latency of the OA advantage for citations.

Gargouri, Y., Hajjem, C., Lariviere, V., Gingras, Y., Brody, T., Carr, L. and Harnad, S. (2010) Self-Selected or Mandated, Open Access Increases Citation Impact for Higher Quality Research. PLOS ONE 5 (10) e13636 http://eprints.ecs.soton.ac.uk/18493/