In this nationally representative sample, we found that having a usual source of care was associated with appropriate treatment with statins. We also found a non-statistically significant trend for an association between usual source of care and attainment of LDL-C goals among patients appropriately treated with statins. Interestingly, socioeconomic factors (i.e. income and education) were not associated use of statins, but were associated with LDL-C goal attainment. Our findings are consistent with prior studies showing that having a usual source of care is associated with improved chronic disease management.9-13
Our findings for goal attainment are consistent with previous data showing that higher socioeconomic status is associated with improved quality of care,21-23
in part due to fewer cost barriers for higher SES persons.24
These difference may reflect differences in provider intensification of treatment or patient differences in adherence to treatment and/or therapeutic life style.25,26
Higher SES is associated with a healthy diet, physical activity and higher rates of obesity.27,28
Each of these factors might contribute to lower goal attainment by SES. Improvements in goal attainment over time has also been previously noted.29
Given the powerful effects of statins on cardiovascular and all-cause mortality,30,31
these results suggest that those lacking a usual source of care may be at higher risk. Specifically, less optimal management of high cholesterol among those without a usual source of care may contribute to higher long-term mortality.
Prior studies suggest that more than 20% of the adult population lack a usual source of care,32
slightly higher than the 19%
in this sample. Consistent with previous studies,32,33
we found that being uninsured, Hispanic, less educated and poor were associated with no usual source of care. In our sample, nearly 50% of those without a usual source of care were uninsured and 45% had household incomes 200% of poverty.
The most frequent reasons cited in past studies for lacking a usual source of care include lack of perceived need (i.e. never/seldom being sick) and cost associated with care.32
The reasons for lack of perceived need are unclear, but may reflect lower illness burden and lack of perceived benefit from preventive care. Costs are a well-recognized barrier to insurance.
Having a usual source of care is often a prerequisite for initiating and continuing chronic disease management. This may be particularly true for cholesterol management. An emergency department or urgent care physician is unlikely to assess a person’s need for statins or to start statin treatment. Similarly, patients who experience an interruption in usual source of care may no longer be able to obtain a prescription for their statin treatment.
Our findings are subject to several limitations. First, our measure of usual of source of care did not distinguish between primary or specialty care or provider continuity. Provider continuity benefits beyond usual source of care alone.2,3,34
It is conceivable that stronger effects might be observed with better measures. Second, our data are cross-sectional. We had no data on pretreatment cholesterol levels, drug doses, or number of times that physicians intensified therapy. We estimated pretreatment lipid levels based on expected reductions in lipids with different lipid lowering drugs. Nonetheless, our findings regarding the association of usual source of care with appropriate treatment with statins were robust in sensitivity analysis in which we varied the percent reduction in cholesterol with treatment. Given the relatively small subsample of participants for whom LDL-C was obtained, we imputed LDL-C based on TC and HDL-C. Comparison of effect sizes between the full sample and subsample showed similar results. The absence of an association between usual source of care and LDL-C was unexpected. This may reflect limitations of the measures discussed above and sample size limitations. Further research is needed to clarify confirm this. Previous studies have noted that African Americans are less likely to receive statins and reach goal attainment.29,35,36
Whether these differences reflect diffusion of statin across groups over time or potential bias in imputation of pretreatment LDL-C levels cannot be determined from these data.
In conclusion, these national data show that lower SES persons and men who are not on statins are more likely to be eligible and among those on statins, these groups are less likely attain their LDL-C goal. Further study is needed to determine the reasons and possible remedies for these disparities.