DISCUSSION

Our analysis suggests that, compared to matched peers, nonmetastatic CRC survivors may be more likely to be diagnosed with hypertension. While the magnitude of the effect appears relatively small, we assert that this is still an important difference when considered from a population health perspective. It is also worth noting that nonmetastatic CRC survivors and controls had very similar rates of primary care visits in the three years post-anchor date and, as a result, similar opportunities to receive a hypertension diagnosis. Specifically, CRC survivors had a mean of approximately 9 primary care visits over the three years post-anchor date (SD 8) and controls had a mean of 8 primary care visits (SD 7). CRC and hypertension share common risk factors (eg, sedentary behavior, poor quality diet, noncompliance with healthy behaviors).29,30 Prolonged sedentary time is associated with increased risk of developing both CRC30 and hypertension, as well as poor blood pressure control.31–33 Among CRC survivors, sedentary time is associated with decreased health-related quality of life34 and higher CRC-specific mortality.35 Although the relationship between risk factors is similar for hyperlipidemia, we saw the opposite association with the likelihood of being diagnosed with hyperlipidemia and/or cholesterol control. While beyond the scope of this project, it is possible that patients who do not follow CRC screening guidelines may have both a higher risk of CRC and be less likely to be compliant with other health behaviors, like blood pressure management. Hyperlipidemia among CRC survivors merits additional study.

Of note, hypertension is a transient side effect of certain chemotherapy regimens, such as bevacizumab for the treatment of metastatic CRC. While our sample includes patients with nonmetastatic disease, we were concerned that some patients might have been prescribed bevacizumab for disease progression. We reviewed VA administrative health data and found that only 7 CRC cases and 11 controls were exposed to bevacizumab during their first year post-anchor date. These small numbers suggest that bevacizumab exposure is not a driver of our results.


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In contrast to a prior analysis,17 we did not find more diabetes diagnoses among CRC survivors in the year following their CRC diagnosis. This may be because the VA patient population, irrespective of cancer status, has a higher prevalence of diabetes (16%) compared to the US (7.2%).36,37 The VA has a strong history of diabetes risk reduction research38–40 and has nationally disseminated two programs targeting diabetes. These programs include the Veterans Affairs Diabetes Prevention Program (VA-DPP) and MOVE! weight management program.41,42 We did not have data about whether people in our cohort participated in these programs.

The association between nonmetastatic CRC and CVD risk-related chronic conditions, such as hypertension, is complex. CRC and CVD share common behavioral risk factors including obesity, physical inactivity, diet, and other lifestyle behaviors.9–12 In Australia, Hawkes and colleagues conducted a telephone-based behavioral change intervention targeting improved dietary habits, increased physical activity, smoking cessation, and alcohol moderation among CRC survivors.43 The intervention improved CRC survivors’ physical activity, dietary habits, and BMI, as well as their psychosocial outcomes.43,44 While this is a promising beginning, there is a need for additional interventions of this type, particularly those targeting hypertension management among CRC survivors. In addition to addressing traditional healthy lifestyle behaviors, future self-management interventions should address medication adherence.

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Medication therapy is often necessary to achieve therapeutic goals for CVD-related chronic conditions and maximum clinical effectiveness.45 Medication nonadherence for chronic disease medications among people with cancer has been documented potentially harming their cardiovascular health.46,47Therefore, we examined adherence to antihypertensive medications. In our study, we found that CRC survivors had lower adherence to a commonly prescribed antihypertensive medication compared to controls. Because we observed poorly managed hypertension and suboptimal medication adherence among CRC survivors, improving medication adherence may be an area for future interventional work in this population.

Our analysis had several limitations. We studied users of the VA health care system who are, on average, older, sicker, and engage in different health behaviors than the general US population.37,48This may impact the generalizability of study findings including generalizing to metastatic CRC, other cancers, or patient populations with a higher proportion of women. Additionally, we did not have data on lifestyle behaviors (eg, diet and physical activity) that might impact CRC and CVD-related chronic conditions. Instead, we relied on BMI prior to diagnosis as a proxy measure. Because we relied on BMI measured in the last six months, we could have missed the inclusion of healthier controls who had no visits and therefore no recent BMI measurements. We also did not have access to information about patients’ diet quality, tobacco, alcohol use, or cancer-related therapies that they received. We considered outcomes within the first year after CRC diagnosis. It is probable that there will be variation at different points in the survivorship trajectory. Despite these limitations, our analysis also had several advantages. We used a national cohort with a large sample size. Additionally, we exactly matched on a myriad of variables that might not be possible in other large administrative datasets (eg, distance from care).

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