Lower prevalence of heart disease but higher mortality risk during follow-up was found among nonrespondents to a cohort study.
OBJECTIVE
The primary aim was to assess the association between response behavior and health status at baseline, and survival in a 5-year follow-up period. A secondary aim was to assess whether reasons for nonresponse were associated with health status at baseline.


METHODS
Data came from a prospective study cohort consisting of 31,349 men and women aged 45-70 years. Objective retrospective and prospective health information derived from general practitioner registries was available for both respondents and nonrespondents.


RESULTS
Results show that among respondents coronary heart disease was more prevalent. Compared with respondents, noncontacts had a higher mortality risk during follow-up. Refusals had hypercholesterolemia more often than did noncontacts, and coronary heart disease or diabetes mellitus less often.


CONCLUSIONS
The paradoxical results that respondents are less healthy at baseline but prospectively have a lower mortality risk may point to a selection effect indicating that the 'worried ill' are more inclined to participate. This effect could imply that observed relationships between risk factors or behaviors and outcomes in cohort studies may be attenuated.
Veenstra
M Y
MY
Addiction Research Institute, Erasmus University Rotterdam, Rotterdam, The Netherlands. m.veenstra@zw.unimaas.nl
Friesema
I H M
IH
Zwietering
P J
PJ
Garretsen
H F L
HF
Knottnerus
J A
JA
Lemmens
P H H M
PH
D017677:Age Distribution; D000368:Aged; D004812:Epidemiologic Methods; D005194:Family Practice; D005260:Female; D006304:Health Status; D006331:Heart Diseases / Q000453:epidemiology* / Q000401:mortality / Q000523:psychology; D006801:Humans; D006937:Hypercholesterolemia / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D009426:Netherlands / Q000453:epidemiology; D018579:Patient Selection; D045808:Refusal to Participate; D015983:Selection Bias