Table A3.

Tests of preconditions for the outcome of 2007 poorer self-rated health status

Precondition	In This Case	Tests	Conclusions
Key time-varying covariates predict exposure	Does health predict academic achievement?	Adjusted linear regression of 1997 academic achievement on perinatal health (low birth weight, spent time in NICU, caregiver-rated health compared to other babies) & 1997 health (caregiver-rated health status, nights spent in hospital birth-1997).	In general, poorer health predicts lower academic achievement. For 1997 achievement, point estimates are driven by NICU and are stronger for perinatal health than 1997 health. For 2002 achievement, perinatal health is stronger predictor than 1997 or 2002 health.
Key time-varying covariates predict exposure	Does health predict academic achievement?	Adjusted linear regression of 2002 academic achievement on perinatal health, 1997 health, and 2002 health (caregiver-rated health status, nights spent in hospital 1997- 2002).
Exposure predicts key time-varying covariates	Does academic achievement predict future health?	Adjusted logistic regression of 2002 poorer caregiver-rated health status on 1997 academic achievement.	In general, higher academic achievement predicts lower odds of poorer health. Stronger evidence for 2007 self-rated health status than 2002 caregiverrated health status.
Exposure predicts key time-varying covariates	Does academic achievement predict future health?	Adjusted logistic regression of 2007 poorer self-rated health status on 1997 and 2002 academic achievement.
Key time-varying covariates predict outcome independent of exposure	Does past health predict 2007 health independent of academic achievement?	Adjusted logistic regression of 2007 poorer self-rated health status on perinatal, 1997, and 2002 health measures, with average 1997–2002 academic achievement included as a covariate	Poorer previous health weakly predicts 2007 poorer self-rated health independent of academic achievement.
Exposure and key time-varying covariates vary over time	Do academic achievement and health vary over time?	Correlation between 1997 and 2002 academic achievement.	Academic achievement and health status do vary over time.
Exposure and key time-varying covariates vary over time	Do academic achievement and health vary over time?	Agreement between 1997, 2002, and 2007 poorer health status measures.	Academic achievement and health status do vary over time.