Population reach and recruitment bias in a maintenance RCT in physically active older adults.
OBJECTIVE
To assess the representativeness of older adults recruited to a physical activity maintenance RCT by conducting sequential comparisons to characterize study sample composition changes occurring between sampling frame construction and study enrollment.


METHODS
Study subjects (N = 1049) were 50 to 70 year old men and women who had increased physical activity within the past year recruited from a Midwestern managed care organization.


RESULTS
Those responding to an initial mailed screener differed on demographic, behavioral, and SES characteristics from those not responding. Compared with ineligibles, eligible individuals were significantly younger, more highly educated, and more likely to report improved health in the prior year. Compared with eligible individuals who did not enroll, enrollees had generally higher education and income.


CONCLUSIONS
Physical activity promotion programs in older adults may have limited reach and substantial volunteer bias. Additional strategies to increase the reach of physical activity interventions into the target population are needed.
Martinson
Brian C
BC
HealthPartners Research Foundation, Minneapolis, MN, USA.
Crain
A Lauren
AL
Sherwood
Nancy E
NE
Hayes
Marcia G
MG
Pronk
Nicolaas P
NP
O'Connor
Patrick J
PJ
D000367:Age Factors; D000368:Aged; D015992:Body Mass Index; D005260:Female; D006279:Health Maintenance Organizations; D006304:Health Status; D006801:Humans; D008297:Male; D008875:Middle Aged; D009043:Motor Activity; D016032:Randomized Controlled Trials as Topic; D015983:Selection Bias