Motivations for (non)participation in population-based health studies among the elderly – comparison of participants and nonparticipants of a prospective study on influenza vaccination

Table 1 Comparison of the participants and nonparticipants of the influenza vaccination study in terms of demographic and health-related variables, %

	Participants of the study (n = 200)	Nonparticipants of the study (n = 531)	p value*
Sex			0.08
Female	43	50
Male	57	50
Median age in years (interquartile range)	72 (68–76)	73 (69–76)	0.11^a
Body Mass Index^b			0.37
Underweight (≤18.49 kg/m²)	1.0	1.6
Normal weight (18.50-24.99 kg/m²)	36	42
Overweight (25.00-29.99 kg/m²)	45	38
Obesity (≥30.00 kg/m²)	18	18
Myocardial infarction			0.68
Yes	6.0	6.8
No	93	91
Don’t know	0.50	0.38
Missing values	0.50	1.7
Cancer			0.54
Yes	20	22
No	80	76
Don’t know	0	1.1
Missing values	0	1.7
Diabetes mellitus			0.008
Yes	7.5	15
No	92	83
Don’t know	0.50	0.57
Missing values	0	1.7
Self-perceived health status			<0.0001
Poor	0	0.19
Fair	9.0	15
Good	64	62
Very good	21	14
Excellent	4.0	0.19
Missing values	2.0	8.0
Ever vaccinated against influenza			0.93
Yes	78	78
No	21	21
Don’t know	1.0	0.19
Missing values	1.5	1.1

*Chi-square test, the category “don’t know” and missing values were not considered in this test
^aMann–Whitney test
^bBody Mass Index (BMI) was calculated using the formula “weight/height²” (kg/m²). Weight and height were objectively measured at the study center in the influenza vaccination study and self-reported by the nonparticipants

ISSN: 1471-2288