Limitations of the current study include the use of state averages
and cross-sectional data that preclude direct inference of causality from
the observed associations. Another limitation is that with only 51
data points for each indicator it is difficult to control for multiple
variables simultaneously in examining the independent association of
health-system indicators. It is also possible that other socio-demographic
factors, for example, educational attainment, which is known
to have an association with poverty and race, might still have some
independent association with the amenable mortality statistic.
Just as it is important in examining health-system indicators to control
for independently associated socio-demographic variables, it is also
important to avoid over-controlling in the analyses, both with multiple
socio-demographic and health-system indicators. Various health-system
indicators are related to each other and interact; for example, lack of
timely access to primary care is related to hospital admissions, and
lack of timely follow-up care is related to hospital readmissions.
Similarly, high rates of hospital readmissions of Medicare beneficiaries
and readmissions of short-stay nursing home patients are likely to be
related.