Since the prevalence of diabetes in the US continues to increase14,15
and women with diabetes are at a higher risk for common cancers showing increased incidence and mortality of cancers7,8,19
, it is of paramount importance that women with diabetes receive the recommended screenings for various cancers. However, our results, at the national level, demonstrate that the screening rates for breast, cervical and colorectal cancers among US women with diabetes are below the Healthy People 2010 Objectives
on cancer screenings for all US women20
To our knowledge, this was the first large study to examine screening rates over time for highly prevalent cancers by diabetes status. Our findings showed that, overall, the screening rates for breast and cervical cancers among US women with diabetes did not change much from 1996 to 2006. Although we did find that the screening rate for colorectal cancer increased from 2002 to 2006, even by 2006, only 63% of US women with diabetes were screened for colorectal cancer. Importantly, we found that the rate of having a FOBT for colorectal cancer screenings among women with diabetes actually decreased from 2002 to 2006. Thus, a wide gap exists between increased risk of cancers and the receipt of cancer screenings in this population.
Two early and one recent case-control studies showed that the rate of having a mammography screening were significantly lower among women with diabetes than among those without diabetes21–23
; however, these studies were limited either by small sample sizes or the inclusion of women aged ≥50 years. In addition, a Canadian study of women aged 50−67 years also showed a lower rate of receiving a mammography screening among those with diabetes than those without 24
. In contrast, our results showing that, among women aged 40−69 years, those with diabetes had a similar screening rate for breast cancer to those without diabetes are apparently opposite to the findings of the previous studies. However, our results partially agree with the previous findings that, among women aged ≥70 years, the screening rate for breast cancer tended to be lower among those with diabetes than among those without (76% versus 79% in 2006, P
0.069). Thus, the apparent differences between our results and those of others may partially result from the different age compositions of the study populations.
For cervical cancer screenings, our results demonstrate that women with diabetes were less likely to be screened for cervical cancer than women without diabetes and that the screening rate for cervical cancer was in a declining trend in 2004 and 2006. Whether or not the provision of diabetes-related services during a health-care visit competes for resources and time availability with preventive services in patients with diabetes remains controversial25
. Nonetheless, attention needs to be directed to the impact that a decline in the screening rate for cervical cancer may have on the health of women with diabetes, and the similar concern exists among women without diabetes as well.
Previous studies of colorectal cancer screenings among women with diabetes have produced mixed results. Bell et al. reported that people with diabetes were as likely or more likely than those without diabetes to report having been screened for colorectal cancer26
; however, a recent study showed that elderly women (≥67 years old) with diabetes were less likely to be screened for colorectal cancer than those without diabetes23
, though the type of colorectal cancer screenings was not analyzed separately in this study23
. Our results demonstrated that women with diabetes were more likely than those without to be screened for colorectal cancer (being screened either by the composite measure of a FOBT and/or a sigmoidoscopy/colonoscopy, or by a FOBT only). In addition, although we have demonstrated that the overall screening rate for colorectal cancer among women with diabetes increased in a linear manner from 2002 to 2006, the screening rate by a FOBT actually decreased during this period; thus, the goal of universal screenings for colorectal cancer in the US remains a distant target.
Our study has several limitations. First, self-reported measures of diabetes status and the receipt of cancer screenings were used, and are thus subject to recall bias. Second, we were unable to exclude women who had already had cancers or had conditions to be diagnosed; therefore, we were not sure whether a test was for screening only or for a diagnostic purpose. Also, we were unable to exclude women for whom screenings for cancers were no longer needed (e.g., women who had had a normal Pap test for many years). Third, for diabetes status, we were unable to distinguish types of diabetes (type 1 versus type 2), which may be differentially associated with an increased risk of cancers. It has been reported that type 1 diabetes accounts for 7% of all diabetes in the BRFSS participants27
. Moreover, detailed information about whether women with diabetes were taking insulin or other diabetes medications was not collected in the present study. Results of a recent study showed that diabetes patients receiving medications were more likely to undergo low endoscopy than those treated by diet control alone28
. In addition, duration of diabetes may also influence the adherence to the cancer screening guidelines among diabetes patients, which could not be evaluated in the present study. Future studies may assess the cancer screening rates by the type, duration and medications of diabetes.
In conclusion, in the US, the proportion of women with diagnosed diabetes who were screened for breast, cervical and colorectal cancers remains below the recommended levels. Women with diabetes were equally likely to be screened for breast cancer, less likely to be screened for cervical cancer, but more likely to be screened for colorectal cancer compared to those without diabetes. Given the important role of physicians, especially obstetrician/gynecologists23
, in promoting preventive screening practices, our results call for more efforts from health-care professionals to educate diabetes patients about the health benefits of cancer screenings and to advise them to adopt good preventive health behaviors.