Commentary: Trajectories, Selection and Cumulative Causation

health status in the elderly: cross-sectional vs. longitudinal estimates. J Clin Epidemiol 2000;53:563–70. 20 Cott CA, Gignac MA, Badley EM. Determinants of self rated health for Canadians with chronic disease and disability. J Epidemiol Community Health 1999;53:731–36. 21 Jylha M, Guralnik JM, Balfour J, Fried LP. Walking difficulty, walking speed, and age as predictors of self-rated health: the women’s health and aging study. J Gerontol A-Bio Sci Med Sci 2001;56:M609–17. 22 Kaplan GA, Roberts RE, Camacho TC, Coyne JC. Psychosocial predictors of depression. Prospective evidence from the Human Population Laboratory studies. Am J Epidemiol 1987;125:206–20. 23 Strawbridge WJ, Walhagen MI, Shema SJ. New NHLBI clinical guidelines for obesity and overweight: Will they promote health? Am J Pub Health 2000;90:340–43. 24 Yen IH, Kaplan GA. Poverty area residence and changes in physical activity level: Evidence from the Alameda County Study. Am J Public Health 1998;88:1709–12.