*2.3. Measurements*

## 2.3.1. Sociodemographic Data

The sociodemographic characteristics used in this study included age (years), gender (male/female), and smoking status. Current smokers were defined as those who smoked at least one cigarette or any type of tobacco per day at the time of the interview. Former smokers were defined as those who previously smoked but had quit within the previous year. Current and former smokers were combined as ever smokers. The remaining participants were defined as nonsmokers.

#### 2.3.2. Physical Activity Levels

Physical activity was evaluated in metabolic equivalent (MET)-minutes per week, using the shortened, translated, and validated in Greek version of the self-reported International Physical Activity Questionnaire (IPAQ) [16]. Those who reported at least 3 MET-minutes per week were classified as physically active. All others were defined as physically inactive.

#### 2.3.3. Anthropometric and Clinical Characteristics

In both studies, weight and height were measured using standard procedures to attain the volunteer's body mass index (BMI) (kg/m2). Overweight was defined as BMI between 25.0 and 29.9 kg/m2, while obesity was defined as BMI >29.9 kg/m2. Waist circumference was measured in the middle between the lowest rib and the iliac crest, using an inelastic measuring tape, to the nearest 0.5 cm. Waist-to-hip ratio was also calculated. Type 2 diabetes mellitus was determined by measuring fasting plasma glucose in accordance with the American Diabetes Association diagnostic criteria (fasting blood glucose >126 mg/dL or use of antidiabetic medication). Participants who had blood pressure levels >140/90 mmHg or who used antihypertensive medications were classified as hypertensive. Fasting blood lipid levels (including high-density lipoprotein-cholesterol (HDL), low-density lipoprotein-cholesterol (LDL), and triglycerides (TG)) were also recorded. Hypercholesterolemia was defined as total serum cholesterol levels >200 mg/dL or the use of lipid-lowering agents, according to the National Cholesterol Education Program Adult Treatment Panel III guidelines [17]. The coefficient of variation for the blood measurements was less than 5%. A cumulative variable (range 0–4) indicating the overall burden of known cardiometabolic risk factors (i.e., obesity and history of hypertension, type 2 diabetes, and hypercholesterolemia) was developed; participants having none of the aforementioned risk factors received a score of 0, having one factor a score of 1, etc.

#### 2.3.4. Dietary Habits Assessment

Among ATTICA study participants, the evaluation of dietary habits was based on a semi-quantitative food-frequency questionnaire (FFQ), originally developed for the European Prospective Investigation into Cancer and Nutrition (EPIC) study [18]. The Greek version of the EPIC questionnaire was provided by the Unit of Nutrition of Athens Medical School, after being translated according to standard literature guidelines [19]. All participants were asked to report the average intake (per week or day) of several food items that they had consumed (during the last 12 months). Similar to the ATTICA study, dietary habits in the MEDIS study were assessed through a semi-quantitative, validated, and reproducible FFQ [20].

The participants were divided into the following three categories based on the type of dietary fats (raw or cooked) consumed: (a) "No culinary use of olive oil", defined as consumption of other types of dietary fats, but not olive oil; (b) "Non-exclusive culinary use of olive oil", defined as the combined consumption of all types of dietary fats; and (c) "Exclusive culinary use of olive oil", defined as sole consumption of olive oil without examining the specific type of olive oil, e.g., extra-virgin, virgin, or refined olive oil, in any of the three aforementioned groups.

#### 2.3.5. Successful Aging Index

Successful aging index (SAI), with potential scores ranging from 0 to 10, previously developed and validated, was employed to evaluate aging for both ATTICA and MEDIS study participants [15]. The full index encompasses health-related social, lifestyle, and clinical factors, including education, financial status, physical activity, BMI, depression, participation in social activities with friends and family, number of yearly excursions, total number of clinical CVD risk factors (i.e., history of hypertension, diabetes, hypercholesterolemia, obesity), and level of adherence to the Mediterranean diet [15].

## 2.3.6. Statistical Analysis

Continuous variables were presented as mean ± standard deviation (SD) and categorical variables as frequencies. Associations between continuous variables and group of participants were evaluated with analyses of variance (ANOVA). To correct for the inflation of Type-I errors in multiple comparisons, Bonferroni's correction was applied. Associations between categorical variables were tested using the calculation of Pearson's chi-squared test. The association between age and type of consumed oil was tested with Pearson's correlation coefficient. Linear regression models were used to evaluate the association between categories of dietary oil consumption (namely no use of olive oil versus (a) combined consumption of olive oil and other dietary fats or (b) exclusive consumption of olive oil) and participants' characteristics (i.e., age, gender, and smoking habits) and the SAI (dependent outcome). Results were presented as unstandardized beta coefficients ± standard error and *p*-value. The STATA software, version 14 (MP & Associated, Sparta, Greece) was used for all statistical analyses. A two-sided *p* < 0.05 was applied as the criterion of significance.
