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Optimism Bias on Health Outcomes Influences Perceived Risk of Diabetes

Feb 25, 2017

Prediabetes, previously undiagnosed diabetes patients interviewed.

KORA FF4 study is a follow-up of the KORA S4 study, a population-based health survey that focuses on a broader spectrum of health-related characteristics, behavior and perceptions rather than diabetes itself. The purpose of this study was to assess how people with UDM estimate their likeliness of having diabetes, to assess how people with prediabetes perceive their diabetes risk, to identify factors associated with perceived diabetes risks, and to analyze whether simple non-invasive diabetes risk scores are superior to perceived risk for the identification of UDM.

In this population-based cohort study, a total of 2,279 subjects participated in the 14-year follow-up FF4 study from the S4 baseline study of 4,261 participants. Follow-up included face-to-face interviews with various physical examinations that were conducted. For ascertainment of type 2 diabetes and prediabetes, all participants received oral glucose tolerance test (OGTT) after fasting for 10h overnight and the mean standard deviation (SD) was 120±1min for the 2h glucose determination. 2003 ADA diagnostic criteria was used to classify previously undiagnosed diabetes (UDM) from impaired fasting glucose (IFG) and impaired glucose tolerance (IGT).

Perception of diabetes risk was based on three questions to estimate the risk of developing diabetes at the present moment, in the next years, and the seriousness of the disease. The covariates (height, weight, waist circumference, systolic, and diastolic blood pressure) were measured based on standard protocols. Two non-invasive diabetes risk scores: KORA (including sex, age, BMI, parental diabetes, hypertension, and smoking) and DESIR (sex, waist circumference, parental diabetes, hypertension, and smoking) were used to compare the perceived risk of having UDM. Also, area under the receiver operating characteristic curve (AROC) was estimated from logistic regression models for subjective risk of UDM.

Out of 2,279 participants, 94 (4.3%) had UDM and 773 (35.4%) had prediabetes with prevalence in men than women. Participants with diabetes had a less favorable metabolic profile and poor subjective health. Participants who perceived their risk of having UDM by categories of glucose regulation were 87.1% in NGT, 83.9% in prediabetes, and 74.2% in UDM. Participants who perceived their risk of developing UDM in the next years by categories of glucose regulation were 14.6% in NGT, 20.6% in prediabetes, and 28.7% in UDM. The subjective risk of diabetes by age was higher in better educated and >60 years old than ≤60 years old. The KORA and DESIR scores discriminated better than the subjective risk assessment between participants with and without UDM. Differences of AROCs were 0.20 (KORA vs. self-perceived risk) and 0.13 (DESIR vs. self-perceived risk).

This study proves that most people hold optimistic bias about their negative health. Three out of four persons with UDM considered themselves having low or very low chances of undetected diabetes. However, participants with prediabetes were more prone to perceive being at risk of diabetes due to self-rated poor health, family history, obesity, female gender, higher education, and being young. The naive optimism concerning health outcomes is more likely due to the lack of previous experience with a disease and if perceived disease risk was controllable. The study included some contradictions between perceived diabetes risks and actual diabetes risk. For instance, association with increased age and perceived risk of developing diabetes was negative because older population poses a lower risk due to shorter life expectancy. Those without a high school degree were perceived as being at risk of developing diabetes due to lack of higher health literacy. Females with prediabetes perceived themselves at risk for diabetes more often than men, although the latter develops more than women. Lastly, persons with prediabetes with higher HbA1c levels or had both IFG and IGT, did not perceive themselves at risk of diabetes due to lack of information on their glycemic state.

The study suggests applying the Protection Motivation Theory (PMT) to diabetes cases to help people build an intention to change their health-related behavior by accepting the severity of disease, perceiving themselves as vulnerable, considering the recommended health behavior to reduce the risks, and having confidence to perform the respective behavior. They used categories instead of percentiles to assess perceived risk because people may have difficulty in transforming subjective risk into probabilities.

In conclusion, it is suggested to focus on early detection of diabetes for the benefit of preventing diabetes with the help of lifestyle changes and medical treatment to reduce cardiovascular morbidity and mortality.

Practice Pearls:

  • People with undiagnosed diabetes or prediabetes underestimate the likelihood of having or developing diabetes, respectively.
  • Early detection of prediabetes and diabetes is beneficial, but optimism bias may overshadow the overall health condition and delay diagnosis.
  • The study is based on a German sample of European descent, thus the results may not be generalizable to another ethnicity and/or culture.


Kowall B, Rathmann W, Stang, A, Bongaerts B, Kuss O, et al. Perceived risk of diabetes seriously underestimates actual diabetes risk: The KORA FF4 study. PLoS ONE. 2017 Jan 31; 12(1): 1-13.

Rathmann W, Kowall B, Heier M, Herder C, Holle R, Thorand B, et al. Prediction models for incident Type 2 diabetes mellitus in the older population: KORA S4/F4 cohort study. Diabet Med. 2010; 27: 1116-1123.

Rathmann W, Strassburger K, Heier M, Holle R, Thorand B, et al. Incidence of type 2 diabetes in the elderly German population and the effect of clinical and lifestyle risk factors: KORA S4/F4 cohort study. Diabet Med. 2009; 26: 1212-1219.