Efficacy of Two Tailored Interventions Promoting Physical Activity in Older Adults Maartje M. van Stralen, MSc, Hein de Vries, PhD, Aart N. Mudde, PhD, Catherine Bolman, PhD, Lilian Lechner, PhD Background: Important health benefits can be obtained if effective low-cost interventions promoting physical activity, especially among older adults, are developed. Design: This RCT investigated the efficacy of two tailored physical activity interventions in promoting awareness, initiation, and maintenance of physical activity among older adults compared to a wait-list control group. Data were collected in 2007. Analyses were conducted in 2008. Setting/ participants: In total, 1971 Dutch older adults (mean age=64 years, 57% women) participated. Intervention: Two tailored physical activity interventions, consisting of three tailored letters delivered during 4 months, were systematically developed. The basic tailored intervention targeted psychosocial determinants alone, while the environmentally tailored interven- tion (intervention-plus) additionally targeted environmental determinants. Main outcome measures: Awareness of personal physical activity behavior, self-reported level of physical activity, and compliance with the physical activity guideline were assessed at baseline, 3 months, and 6 months. Results: Intervention participants became more aware of their personal physical activity level at 6 months (OR Ibasic =1.7, OR Iplus =1.6) and were significantly more physically active at 3 (EffectSize[ES] Ibasic =0.20, ES Iplus =0.20) and 6 months (ES Ibasic =0.30, ES Iplus =0.35) when compared to control participants. Moderation analyses showed that the interventions enhanced physical activity initiation at 3 (ES Ibasic =0.26, ES Iplus =0.21) and 6 months (ES Ibasic =0.32, ES Iplus =0.27) among participants insufficiently active at baseline, and induced maintenance at 6 months among participants sufficiently active at baseline (ES Ibasic =0.33, ES Iplus =0.34) when compared to the control condition. No differences between the intervention arms were found. Conclusions: The results indicate that tailoring can be an effective tool in attaining and enhancing awareness, initiation, and maintenance of physical activity among older adults. Targeting environmental determinants in addition to psychosocial determinants, however, did not result in an additional increase in physical activity behavior. Trial registration: This study was registered with the Dutch Trial Register NTR 920. (Am J Prev Med 2009;37(5):405– 417) © 2009 American Journal of Preventive Medicine Introduction P hysical activity has been demonstrated to play an important role in health promotion and quality of life as people age. 1,2 However, in most West- ern countries, such as the U.S. and the Netherlands, less than 60% of the general population complies with the international guideline of 30 minutes of moderate physical activity a day at least 5 days per week, 3 decreas- ing to less than 50% among older adults. 4–7 As the population in Western countries ages, this inactivity is becoming an increasing problem. Therefore, effective low-cost interventions (e.g., print-tailored) promoting physical activity among this age group are needed. Research has shown that physical activity behavior of older adults can be effectively changed through inter- vention programs. 8 –15 Computer-tailored intervention, in which computer technology adapts health informa- tion to the specific needs and characteristics of a person, 16,17 is a low-cost strategy that has the potential From the Department of Psychology (van Stralen, Mudde, Bolman, Lechner), Open University of the Netherlands, Heerlen; EMGO Institute for Health and Care Research (van Stralen), VU University Medical Center, Amsterdam; and Department of Health Promotion (de Vries), Maastricht University, Maastricht, the Netherlands Address correspondence and reprint requests to: Maartje M. van Stralen, MSc, VU University Medical Center, EMGO Institute for Health and Care Research, Van der Boechorststraat 7, 1081 BT Amsterdam, the Netherlands. E-mail: mm.vanstralen@vumc.nl. 405 Am J Prev Med 2009;37(5) 0749-3797/09/$–see front matter © 2009 American Journal of Preventive Medicine • Published by Elsevier Inc. doi:10.1016/j.amepre.2009.07.009