Abstract
Background: The Respiratory Health in Northern Europe (RHINE) study started in 1990 and has for more than 20 years been conducted in study centers in Denmark, Sweden, Norway, Iceland and Estonia.
Aims: To examine if and how non-response over time affects prevalence and association estimates.
Methods: Participants answered questionnaires in 1990, 2000 and 2011-12. We compared age and sex distribution between those who responded only in 1990, and those who responded in both 1990 and 2011-12. We compared baseline prevalence of 10 respiratory symptoms and also associations between age/sex and asthma, rhinitis and wheeze between all 1990 responders and those who also responded in 2011-12.
Results: Of 21673 subjects aged 20-44 at baseline, 61% participated also in 2011-12 (N=13142). Long-term responders were slightly older than non-responders in 2011-12 (32.1 yrs versus 31.0 yrs (p<0.05)), and a larger proportion was female (53% vs 48% (p<0.05)). There was a slightly lower baseline prevalence (p<0.05) of wheeze, dyspnea and cough symptoms among long-term responders (e.g. waking with dyspnea 4.3% (3.9, 4.7) and chest tightness 10.7% (10.1, 11.3)) than among the total population (e.g. waking with dyspnea 4.8% (95%CI 4.5, 5.2) and chest tightness 11.4% (95%CI 10.9, 11.8)), but no difference in asthma and rhinitis outcomes. Association measures between age/sex and asthma, rhinitis and wheeze were not affected by long-term follow-up.
Conclusions: Long-term responders were slightly older and more often women than non-responders. Long-term responders had slightly less baseline respiratory symptoms than the total baseline population, but associations between age/sex and respiratory symptoms do not differ.
- © 2013 ERS