Missing-data analysis: socio- demographic, clinical and lifestyle determinants of low response rate on self- reported psychological and nutrition related multi- item instruments in the context of the ATTICA epidemiological study

Table 2 Average number of missing items in the MedDietScore scale, according to the participants’ demographic, clinical and lifestyle characteristics; the ATTICA epidemiological study

	Mean (SD¹)	p-value²	IRR (95% CI)³	p-value⁴
Demographic characteristics
Sex
Male	2.07 (2.65)	0.390	1.00	–
Female	2.17 (2.70)	0.390	1.05 (0.99, 1.11)	0.114
Educational level⁵
No formal studies	2.83 (2.60)	0.002	1.61 (1.29, 2.00)	< 0.001
Primary education	2.41 (2.61)		1.37 (1.19, 1.58)	< 0.001
Secondary education	2.69 (2.90)		1.53 (1.34, 1.74)	< 0.001
Higher education	1.76 (2.41)		1.00	–
Clinical characteristics
Obesity⁶
Yes	2.05 (2.63)	0.507	1.04 (0.97, 1.12)	0.222
No	1.97 (2.58)	0.507	1.00	–
Diabetes Mellitus⁷
Yes	1.72 (2.35)	0.007	1.31 (1.18, 1.45)	< 0.001
No	1.32 (2.05)	0.007	1.00	–
Hypertension⁸
Yes	2.07 (2.64)	0.448	0.96 (0.90, 1.02)	0.163
No	2.16 (2.71)	0.448	1.00	–
Hypercholesterolemia⁹
Desirable levels (< 200 mg/dL)	1.35 (2.18)	< 0.001	0.63 (0.58, 0.69)	< 0.001
Borderline levels (200–239 mg/dL)	1.89 (2.52)		0.89 (0.82, 0.96)	0.002
High levels (> 240 mg/dL)	2.13 (2.57)		1.00	–
Lifestyle characteristics
Type of lifestyle¹⁰
Unhealthy lifestyle	2.86 (2.78)	0.022	1.20 (1.09, 1.33)	< 0.001
Healthy lifestyle	2.38 (2.63)	0.022	1.00	–

Notes: 1 SD= Standard Deviation. 2 p-value is based on the Independent samples t-test when the categorical characteristic has two categories, and on the one-way Analysis of Variance (ANOVA) when the categorical characteristic has at least three categories. 3 IRR= Incidence Rate Ratio, CI= Confidence Interval. 4 p-value refers to the comparison of each category to the baseline category. 5 Educational level is defined as follows: No formal studies= 0 years, Primary education≤ 6 years, Secondary education≤ 12 years, and Higher education> 12 years. 6Obesity was defined as Body Mass Index (BMI)≥ 30 kg/m2. 7 Diabetes mellitus was defined as a fasting blood sugar > 125 mg/dl or the use of antidiabetic medication. 8 Patients whose average blood pressure levels were greater or equal to 140 / 90 mm Hg or were under antihypertensive medication were classified as hypertensives. 9 The definition of hypercholesterolemia was based on the total serum cholesterol levels. 10 Healthy lifestyle= non- smokers and physically active participants, Unhealthy lifestyle= Either smokers, or physically inactive participants

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