Insulin Injection Omission – Demographic and disease factors

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We found that respondents with higher household income, but not individuals with more education, were less likely to skip insulin injections they knew they should take. This may reflect easier access to medications and supplies among individuals with higher income, but it is also likely that higher socioeconomic status is associated with more access to diabetes education, higher health literacy, greater control over one’s daily routines, and better problem-solving skills. Our study appears to be among the first to identify an association between socioeconomic status and insulin omission. Future research should seek to identify potential mediators of this relationship, i.e., what links lower socioeconomic status to insulin omission.

Contrary to earlier reports, we found no racial/ethnic differences in intentional insulin omission. This may be because we did not have enough nonwhite respondents to examine the different racial/ethnic groups separately. Alternatively, this may be due to our controlling for income and education in the analysis, thereby eliminating the confounding of race/ethnicity with socioeconomic status.

Much prior research has suggested that intentional insulin omission is common among female adolescents with type 1 diabetes, serving as a weight control strategy and sometimes linked to eating disorders. We found that students (who were younger than nonstudents) were more likely to skip injections they knew they should take, but this behavior was not more common among women than it was among men. We found no overall association between age and intentional insulin injection omission among patients with type 1 diabetes, suggesting that patients with type 1 diabetes “age-out” of this behavior by early adulthood, when they complete their education. Ascertaining the validity of this interpretation would require following youth with type 1 diabetes as they age into adulthood to determine change in rate of insulin omission.

Our finding that, among individuals with type 2 diabetes, older respondents were less likely to skip insulin injections is consistent with earlier studies. This suggests that there are parallel aging-out processes among individuals with type 1 and type 2 diabetes, but in type 2 diabetes, this process takes place later in the life course (almost all people with type 2 diabetes are diagnosed as adults). Ascertaining the validity of this interpretation would require following adults with type 2 diabetes as they age to determine change in rate of insulin omission.

Having type 2 diabetes was itself associated with higher levels of intentional omission of insulin injections. The beta for this variable (0.226) was approximately twice the size of the unadjusted eta (0.095), reflecting the fact that controlling for confounding factors (such as age and number of daily injections) revealed a stronger underlying association. The independent association of type 2 diabetes with increased insulin omission may reflect the fact that patients with type 2 diabetes have a residual insulin response, reducing the immediate consequences of omitting an injection. Thus, these individuals may feel less vulnerable to the effects of skipping insulin injections they know they should take. Interestingly, whereas duration of diabetes was associated with the frequency of insulin injection omission, regression analysis revealed that duration of diabetes did not make an independent contribution to this behavior. That is, although insulin omission may be less common among individuals with longer duration of diabetes, this is likely a function of other factors such as age and type of diabetes rather than of duration per se.