Limitations of this study include its retrospective chart review design. This design is susceptible to incorrect recording of events. The primary outcome, aggregate adverse cardiovascular events, may have been incorrectly recorded in the medical record as other diseases, such as coronary artery disease or heart disease, and therefore not captured by ICD 9 code retrieval. Also, important information, such as laboratory data, disease, and medication adherence, may not have been documented for all patients. Of note 1 patient in the fish oil and statin combination cohort did not have any recorded laboratory data, disease, or adherence data.
Another limitation is lack of access to medical notes from non-VA providers, which can result in missed data collection. To reduce this limitation, the study excluded veterans that received non-VA fish oil, statins, or other hyperlipidemia medications for > 1 year. Veterans were included only if they used VA-provided fish oil or statins. This inclusion and exclusion criteria reduced the chance of missing data from other facilities because it favored inclusion of only subjects that received care exclusively through the VA.
Last, on study initiation it was not realized that fish oil was not provided by the health care system until about the year 2004. This resulted in less risk days for the fish oil and statin cohort. However, Kaplan Meier analysis lessens this issue from being a confounder. Time to event rates for both the primary and secondary outcomes were similar and most likely would have continued to trend together with the same therapy duration.
Fish oil and statin combination therapy when compared with statin monotherapy failed to show that a statistically significant difference exists in the rates of MI, stroke, transient ischemic attack, coronary artery bypass graft, and percutaneous intervention. The clinical difference of fish oil and statin combination therapy vs statin monotherapy is most likely small or nonexistent. From our literature search, this is the only study concerning the use of fish oil and statin combination therapy in the veteran population. It is most likely that fish oil and statin combination therapy and statin monotherapy are similar for the reduction of time to aggregate adverse cardiovascular events and all-cause mortality in the veteran population.
This material is the result of work supported with resources and the use of facilities at the Fargo VA Healthcare System.