The Danish National Survey of Diet and Physical Activity (DANSDA) 1995-2011-2013: Study design, study participants, participation rate and underreporting.

Aim: This study describes the study design, study participants, participation rate and underreporting in the Danish National Surveys of Diet and Physical Activity (DANSDA) from 1995 to 2011-2013.

Methods: DANSDA are government-funded surveys of food and nutrient intake, physical activity and lifestyle, undertaken to support nutritional policy, risk assessment and public health research. The surveys are cross-sectional based on primarily simple random samples (ages 1-80 years in 1995, 4-75 years in 2000-2013) drawn from the Danish Civil Registration System. Approximately 4800 individuals in 1995, 8200 in 2000-2002, 8400 in 2003-2008 and 7300 in 2011-2013 were invited to participate. Participants completed a seven-day food diary, a physical activity questionnaire (2000-2008), a step diary (2011-2013) and a face-to-face interview. Self-reported anthropometrics (1995-2013) were supplemented with device-based measures (2011-2013). Pedometers were included in 2011-2013.

Results: The number of participants included per survey round was 3100-4400. Participant rates decreased from 66% (1995) to 54% (2011-2013). Non-participation was primarily refusal. Ages 18-30 years, 61-75 years (2000-2013), 61-80 years (1995) and low educated and individuals living alone were underrepresented. Underreporting of energy intake among adults ranged from 14% (1995) to 26% (2008).

Conclusions: