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Web-based interventions are popular for promoting healthy lifestyles such as physical activity. However, little is known about user characteristics, adherence, attrition, and predictors of repeated participation on open access physical activity websites.
The focus of this study was Active-online, a Web-based individually tailored physical activity intervention. The aims were (1) to assess and compare user characteristics and adherence to the website (a) in the open access context over time from 2003 to 2009, and (b) between trial participants and open access users; and (2) to analyze attrition and predictors of repeated use among participants in a randomized controlled trial compared with registered open access users.
Data routinely recorded in the Active-online user database were used. Adherence was defined as: the number of pages viewed, the proportion of visits during which a tailored module was begun, the proportion of visits during which tailored feedback was received, and the time spent in the tailored modules. Adherence was analyzed according to six one-year periods (2003-2009) and according to the context (trial or open access) based on first visits and longest visits. Attrition and predictors of repeated participation were compared between trial participants and open access users.
The number of recorded visits per year on Active-online decreased from 42,626 in 2003-2004 to 8343 in 2008-2009 (each of six one-year time periods ran from April 23 to April 22 of the following year). The mean age of users was between 38.4 and 43.1 years in all time periods and both contexts. The proportion of women increased from 49.5% in 2003-2004 to 61.3% in 2008-2009 (
Adherence, patterns of use, attrition, and repeated participation differed between trial participants and open access users. Reminder emails to encourage repeated participation were effective for trial participants but not for registered open access users. These issues are important when interpreting results of randomized controlled effectiveness trials.
In recent years,Web-based interventions targeting health issues such as nutrition [
To maximize effectiveness, it is important for developers of such interventions to know more about user characteristics, adherence (the extent to which individuals use the content of the Internet intervention) [
Few studies have described use and users of open access websites in the domain of smoking [
In Switzerland, a Web-based tailored physical activity intervention (Active-online) [
The aims of the present study were: (1) to assess and compare user characteristics and adherence to the website (a) in an open access context over time from 2003 to 2009, and (b) between participants in an RCT and open access users (all open access users and the subgroup of registered open access users only), and (2) to analyze attrition and potential predictors of repeated use of the website in trial participants compared with registered open access users.
Active-online is an individually tailored program to promote physical activity targeting adults aged 30 to 60 years. Active-online is freely available on the Internet in the three main languages of Switzerland: German, French, and Italian. At the start of the program, users find a language selection page followed by a welcoming page that explains the program and provides additional information and motivational material (see
Users may visit Active-online without registering, or they may register. Registration is very brief and involves leaving an email address. Registered users receive a password which allows them to revisit the website and follow changes in their physical activity behavior. Registered users receive reminder emails that contain a link to revisit the website after 2, 4, and 7 months.
Screenshot of the welcoming page of Active-online
Structure of Active-online and the tailored intervention modules
The HEPA module offers a maximum of four individually tailored feedbacks based on the transtheoretical model of behavior change [
The RCT is described in detail elsewhere [
In April 2003, Active-online was officially launched with a promotional event. Data from the open access period were included for six one-year time periods through April 2009. Each one-year time period started on April 23 and ended on April 22 of the following year. Data from the effectiveness trial were included from May 1, 2006, through September 30, 2007.
The total number of visits on Active-online (including visits on the welcoming page) was available from the Internet provider. However, the absolute numbers were difficult to interpret because these depended on the software used to assess them and whether visits by web crawlers could be identified, for example. For both open access users and trial participants, visits on Active-online were captured in the Active-online user database as soon as the new browser window for the selection of one of the two tailored modules was opened (see
For each visit that was captured in the Active-online user database, starting time and date, finishing time and date, number of pages viewed, and time spent within the tailored modules were recorded in addition to responses to the questionnaires preceding each tailored feedback.
During the study period, between April 23, 2003, and April 22, 2009, more than 250,000 visits were counted on Active-online (including visits not going beyond the welcoming page and excluding visits by web crawlers). For the present study, only those visits that went beyond the welcoming page and were recorded in the Active-online user database during the study period were included. These numbered 113,290.
Inclusion and exclusion of records used in the analyses
Of the 110,776 visits, 108,673 were recorded in the open access context and 2103 during the RCT. For the analysis of time trends, open access visits were stratified according to the six one-year periods between 2003 and 2009. The number of recorded and first visits and the proportion of first visits resulting in registration are displayed in
Recorded website visits in the open access context (according to the six time periods from 2003-2009) and during the RCT
Open Access Program Use | Number of Visits Recorded in Database | Number of First Visits (% of Recorded Visits) | Number of First Visits Resulting in |
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2003-2004 | 42,626 | 41,699 (97.8%) | 2263 (5.4%) |
2004-2005 | 25,392 | 25,026 (98.6%) | 784 (3.1%) |
2005-2006 | 12,776 | 12,517 (98.0%) | 592 (4.7%) |
2006-2007 | 9847 | 9539 (96.9%) | 610 (6.4%) |
2007-2008 | 9689 | 9451 (97.5%) | 513 (5.4%) |
2008-2009 | 8343 | 8140 (97.6%) | 322 (4.0%) |
Total (2003-2009) | 108,673 | 106,372 (97.9%) | 5084 (4.8%) |
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aTrial participants were automatically registered within Active-online.
The proportion of women among Active-online users and the mean age of visitors were included in the analyses as demographic variables. The main measure of physical activity was the proportion meeting the current Swiss recommendations for health-enhancing physical activity (HEPA): 30 minutes or more of moderate intensity activities on 5 or more days per week or 20 minutes or more of vigorous intensity activities on 3 or more days per week [
Adherence, defined as the extent to which individuals experienced the content of the website [
Attrition describes the phenomenon that participants stop using the intervention [
Comparisons are reported between trial participants (all of whom were registered, according to the study design), open access users (including both registered and unregistered open access users), and the subgroup of open access users who had registered and received a password to revisit Active-online.
Demographic variables were compared between open access users and trial participants using
Nonusage attrition curves were based on the proportion of visitors still using the website up to a specific number of weeks or months after the first visit versus those who had stopped using it. The date of each user's last visit was designated as the date when program usage ended. The nonusage attrition curves are presented over 18 months (considered a suitable timeframe for trial participation) and over 12 weeks (for comparison with other published attrition curves). Similarly, attrition curves based on the duration of single visits (first visits and longest visits) are presented, which correspond to the proportion of visitors who had continued to use the intervention within a single session versus those who had ended the session after a specific number of minutes. Duration was defined as the time spent in the tailored modules as recorded in the user database; therefore, individuals that did not enter a tailored module have been assigned a duration of zero. STATA 9.2 (STATACorp LP, College Station, TX, USA) was used for the analyses.
The yearly number of open access visits recorded in the Active-online database decreased from 42,626 in 2003-2004 to 8343 in 2008-2009. In the open access context, the proportion of women using Active-online increased from 49.5% in 2003-2004 to 61.3% in 2008-2009 (
Among open access Active-online users, 55.1% were women, while 74.9% of trial participants were women (
There were differences, but no consistent trends over time, in adherence to Active-online among open access users (based on the analysis of first visits). In general, use of the intervention among open access users was higher in 2003-2004, 2005-2006, and in 2006-2007, but lower in 2004-2005 and after 2007 (
For first visits, adherence to Active-online was highest for registered open access users (
Analyzing adherence according to longest visit, we found that results remained very similar to the results for first visit among open access users, indicating that the first and longest visit were identical among these users. This was not true for trial participants, however. As was the case for first visits, registered open access users achieved the highest adherence when results were based on longest visit. Trial participants' adherence was considerably higher during the longest visit than during the first visit (indicating that the first visit was not the longest visit) and was higher compared with all open access users.
Adherence at first visit according to time periods during open access use 2003-2009, and at first and longest visit according to open access context and randomized controlled trial
Median (IQR) Number of Pages Viewed per Visit | Number of Visits (%) When a Tailored Module Was Started | Number of Visits (%) When ≥ 3 Minutes Spent in the Tailored Modules | Number of Visits (%) When At Least One Tailored Feedback Was Received | Median (IQR) Minutes Spent in Tailored Module per Visit (When a Module Was Started) | Median (IQR) Minutes Spent in Tailored Modules per Visit (if ≥ 3 Minutes Spent in Modules) | |
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2003-2004 | 16 (9-28) | 29,967 (71.9%) | 19,349 (46.4%) | 24,973 (59.9%) | 4.2 (1.8-11.4) | 8.4 (4.8-15.6) |
2004-2005 | 11 (4-21) | 16,465 (65.8%) | 9341 (37.3%) | 13,132 (52.5%) | 3.6 (1.2-8.4) | 7.2 (4.2-13.8) |
2005-2006 | 19 (11-31) | 8851 (70.7%) | 5593 (44.7%) | 7277 (58.1%) | 4.2 (1.8-11.4) | 9.0 (4.8-15.6) |
2006-2007 | 21 (13-32) | 6661 (69.8%) | 4154 (43.5%) | 5716 (59.9%) | 4.2 (1.8-10.8) | 8.4 (4.8-15.6) |
2007-2008 | 19 (11-30) | 6015 (63.6%) | 3728 (39.4%) | 5152 (54.5%) | 4.2 (1.8-10.2) | 8.4 (4.8-14.4) |
2008-2009 | 16 (11-25) | 4818 (59.2%) | 2639 (32.4%) | 4090 (50.3%) | 3.0 (1.2-7.8) | 6.6 (4.2-11.4) |
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< .001 | < .001 | < .001 | < .001 | < .001 | < .001 |
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Open access: all users | 16 (9-27) | 72,777 (68.4%) | 44,804 (42.1%) | 60,340 (56.7%) | 4.2 (1.8-10.2) | 8.4 (4.8-15) |
Open access: registered |
42 (30-57) | 4892 (96.2%) | 4643 (91.3%) | 4629 (91.1%) | 15.0 (8.4-24.0) | 15.6 (9.6-24.6) |
Trial participants | 7 (2-21) | 322 (38.5%) | 265 (31.7%) | 250 (29.9%) | 9.0 (3.6-15.6) | 10.8 (6.0-16.2) |
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< .001 | < .001 | < .001 | < .001 | < .001 | < .001 |
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Open access: all users | 16 (9-27) | 72,943 (68.5%) | 44,985 (42.2%) | 60,531 (56.8%) | 4.2 (1.8-10.2) | 8.4 (4.8-15.0) |
Open access: registered |
43 (31-57) | 5021 (96.5%) | 4789 (92.0%) | 4779 (91.8%) | 15.6 (9.0-24.6) | 16.2 (10.2-25.2) |
Trial participants | 23 (8-38) | 626 (74.4%) | 554 (65.8%) | 549 (65.2%) | 12.0 (5.4-18.6) | 13.2 (7.8-20.4) |
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< .001 | < .001 | < .001 | < .001 | < .001 | < .001 |
aEach one-year time period started on April 23 and ended on April 22.
b
c
Nonusage attrition curves for open access users and trial participants over 18 months
Nonusage attrition curves for open access users and trial participants over 12 weeks
Attrition curves for the duration of the first visit for open access users and trial participants
Attrition curves for the duration of the longest visit for open access users and trial participants
In total, 1312 (25.8%) of open access users who registered and received a password and 558 (67.3%) of the trial participants returned for a repeated visit (
Predictors of repeated participation for registered open access users and for trial participants
Registered Open Access Users (2003-2009) | Trial Participants | ||||||||
N | % Repeated Visits | Unadjusted OR (95% CI) | Adjusted ORa(95% CI) | N | % Repeated Visits | Unadjusted OR (95% CI) | Adjusted ORa(95% CI) | ||
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Female | 2,886 | 24.1 | 1.00 | 1.00 | 626 | 66.3 | 1.00 | 1.00 | |
Male | 2,197 | 28.0 |
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210 | 70.5 | 1.21 (0.86-1.70) | 0.79 (0.39-1.62) | |
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< 30 | 1,270 | 20.5 | 1.00 | 1.00 | 151 | 53.6 | 1.00 | 1.00 | |
30-45 | 2,111 | 25.9 |
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324 | 65.7 |
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1.61 (0.71-3.66) | |
46-60 | 1,370 | 28.2 |
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269 | 75.1 |
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> 60 | 332 | 35.8 |
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92 | 72.8 |
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1.72 (0.57-5.20) | |
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Yes | 1,587 | 24.4 | 1.00 | 1.00 | 347 | 70.3 | 1.00 | 1.00 | |
No | 2,697 | 25.8 | 1.07 (0.93-1.24) | 1.11 (0.96-1.29) | 489 | 65.2 | 0.79 (0.59-1.07) | 0.76 (0.56-1.03) | |
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Not available | ||||||||
Yes | 125 | 64.8 | 1.00 | 1.00 | |||||
No | 711 | 67.8 | 1.14 (0.77-1.70) | 1.03 (0.69-1.56) | |||||
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Not available | ||||||||
<= 25 | 501 | 67.5 | 1.00 | 1.00 | |||||
25-30 | 227 | 68.7 | 1.06 (0.76-1.48) | 0.93 (0.65-1.32) | |||||
> 30 | 106 | 64.2 | 0.86 (0.56-1.34) | 0.79 (0.50-1.25) | |||||
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Not available | ||||||||
Compulsory school | 29 | 51.7 | 1.00 | 1.00 | |||||
Apprenticeship | 289 | 67.8 | 1.97 (0.91-4.24) | 1.73 (0.78-3.81) | |||||
High school | 124 | 63.7 | 1.64 (0.73-3.70) | 1.82 (0.79-4.19) | |||||
Higher professional education, upper |
189 | 70.9 |
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1.95 (0.86-4.41) | |||||
University | 205 | 67.8 | 1.97 (0.90-4.31) | 1.74 (0.78-3.91) | |||||
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Not available | ||||||||
Swiss | 737 | 68.4 | 1.00 | 1.00 | |||||
Non Swiss | 99 | 59.6 | 0.68 (0.44-1.05) |
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aAdjusted for sex, age category, and whether HEPA recommendations were met. Additional adjustment for the other potential predictors in the model (RCT only) did not change the results.
The present study aimed to assess user characteristics, adherence, attrition, and predictors of repeated use in trial participants and open access users of a Web-based physical activity intervention. The most important findings were differences in adherence, attrition, and repeated participation between trial participants and open access users. Furthermore, reminder emails had a differential effect on attrition in trial participants and open access users. Assessing the data over time, there was an increase in the proportion of women using Active-online but no consistent trends in terms of adherence.
The yearly number of recorded visits on Active-online decreased from over 40,000 in 2003-2004 to less than 9,000 in 2008-2009. The most likely reason for this decrease was a decline in promotional efforts because there has been no active promotion of the website since 2008. Despite the decrease in the absolute number of visits, it is encouraging that even without active promotional strategies, Active-online still yielded around 23 visits per day in 2008-2009. Furthermore, no consistent time trends in adherence and patterns of individual intervention use were observed in open access users between 2003 and 2009.
Different reasons may be responsible for the increase in the proportion of women using Active-online between 2003 and 2009. For one thing, the proportion of women using the Internet has increased steadily in Switzerland from 23% in 1997 to 44% in 2006 [
Trial participants differed in several ways from open access users. Adherence of trial participants during the first visit was generally lower. Only the small proportion that became involved with the intervention spent as much or more time in the tailored modules compared with open access users. The additional baseline data assessment in the trial context is a likely reason for the low use during the first visit in trial participants. However, comparing trial participants and participants of the feasibility study [
Trial participants were significantly more likely to visit the website repeatedly compared with open access users. Furthermore, when analyzing longest visits (
In the open access context, registration did not achieve high levels of repeated participation (
Open access users and trial participants who started a tailored module spent an average of 7.5 and 9.2 minutes in the modules, respectively. Other studies have found similar visit durations, for example, an average of 9 minutes was found among participants of a randomized study regarding another physical activity website [
Only about 2% of the open access visits on Active-online between 2003 and 2009 were repeated visits (
In a previous study, the main predictors of repeated participation in a behavior change program for healthy body weight were older age, never having smoked, meeting the guidelines for moderate physical activity and vegetable consumption, and being obese [
Nonusage attrition was much higher for open access users (all open access users as well as the subgroup of registered open access users only) than for trial participants. Similar, although less pronounced, results have been reported for spontaneous users of a cognitive behavior therapy website compared with participants in an RCT through the same website [
The open structure of Active-online has advantages regarding dissemination and use of the intervention in that visitors are free to switch between modules, to open several windows concurrently, and to use the tailored intervention without registering. Thus, more individuals may be willing to participate in the intervention. However, this open structure also has some limitations. For example, a repeated visit of an unregistered user is recorded as a new first visit. Furthermore, an individual may open more than one tailored intervention browser window resulting in multiple new visits being recorded in the database. Individuals are also free to stop the intervention at any point, which can produce large amounts of missing data if the intervention is terminated before all questionnaires are completed. Nevertheless, our study results provide insight into an open access Web-based physical activity intervention delivered under real-world conditions and allow comparisons of use and users over time and in different contexts.
Another limitation is the lack of information on the sociodemographic background of open access users and additional potential predictors of repeated website usage. During the development of Active-online it was decided not to include questions ascertaining sociodemographic variables (with the exception of sex and age) at the start of the tailored intervention. There was a concern that this may discourage entering the intervention for individuals who may be unwilling to reveal personal information or to spend time completing questions not related to tailored feedback. Ideally, a newer version of Active-online may include a brief questionnaire with questions related to smoking, BMI, socioeconomic status, education, and nationality, for example. Finally, we compared open access users visiting Active-online between 2003 and 2009 with trial participants visiting the website between 2006 and 2007. Thus, potential period effects may have influenced the differences observed in our analyses. However,
It is important to acknowledge that adherence, patterns of individual use, repeated participation, and attrition on a Web-based individually tailored physical activity intervention may differ between open access users and trial participants. Moreover, reminder emails to encourage repeated participation may not have the same effect in different contexts. These issues are important when interpreting and generalizing results of randomized controlled effectiveness trials.
Active-online was developed at the Institute of Social and Preventive Medicine at the University of Zurich and was funded and supported by the Swiss Federal Office of Sport, Health Promotion Switzerland, Allez Hop, Suva, and Qualitop. The authors would like to thank Thomas Suter who programmed the website.
None declared.
body mass index
confidence interval
health-enhancing physical activity
interquartile range
randomized controlled trial