This review compared interventions based on the transtheoretical model (TTM) with other interventions or usual care. The authors concluded that TTM-based interventions had some short-term benefits over controls but few studies demonstrated benefits beyond 6 months. The review had some methodological and reporting limitations but the conclusions appear suitably cautious.

To assess whether interventions based on the transtheoretical model (TTM) are more effective than other interventions in promoting physical activity.

MEDLINE and PsycINFO were searched from 1982 to 2001. The keywords used were 'transtheoretical', 'stages of change', 'activity' and 'exercise'. Only English language studies were sought. The reference lists of identified studies were checked.

Study designs of evaluations included in the review

No specific criteria for the study design were given. The included studies were randomised controlled trials (RCTs), non-randomised studies and uncontrolled before-and-after studies.

Specific interventions included in the review

Interventions based on the TTM (or 'stages of change') to promote physical activity were sought. The specific interventions in the included studies were counselling and/or written information. These were compared with usual care or non TTM-based information or counselling. The duration of follow-up ranged from 3 weeks to 24 months.

Participants included in the review

All the participants were adults (over 16 years of age) who were living in the community. The included studies recruited patients mainly from primary care centres, advertising campaigns, workplaces and diabetes clinics. Several studies specifically recruited adults at cardiovascular risk (with one or more modifiable risk factors). All of the included studies were carried out in the USA or UK.

Outcomes assessed in the review

The included studies reported on 'stage of change' of the TTM for physical activity. Some measurement of the physical activity levels before and after the intervention also had to be reported. Physical activity was mostly evaluated by self-reported questionnaires or, in a few studies, by physical fitness assessments or electronic motion sensors. The outcomes were classified as short term (6 months or less) or long term (more than 6 months).

How were decisions on the relevance of primary studies made?

The authors did not state how the papers were selected for the review, or how many reviewers performed the selection.

Aspects of 'quality' were described and discussed for each study. Such aspects included the methods of recruiting participants, the length of follow-up, study design, type and delivery of TTM intervention and control group, and measurement of physical activity. The authors did not state how the papers were assessed for quality, or how many reviewers performed the quality assessment.

The authors did not state how the data were extracted for the review, or how many reviewers performed the data extraction. Data were extracted on the numbers of patients recruited and completing the study, country of study, experimental intervention and control, length of follow-up and main results.

How were the studies combined?

The studies were combined in a narrative discussion and presented in tabular format.

How were differences between studies investigated?

Differences between the studies were described narratively. The authors attempted to explain any differences in terms of the intensity of the intervention, the participants recruited, differences in the nature of the experimental intervention, and the length of follow-up.

Sixteen studies (7,465 participants recruited) were included: 13 RCTs (6,306 patients recruited), 2 non-randomised controlled trials (549 patients recruited) and one uncontrolled before-and-after study (610 patients recruited).

There was substantial heterogeneity in the programmes reviewed in terms of the intervention design, recruitment methods, participants recruited, outcome measures, length of follow-up, and results; this made comparison difficult. Losses to follow-up were often high, ranging from 3 to 61%.

In the short term (less than 6 months), most studies (11 out of 15) reported some significant benefit of TTM-based interventions over control conditions, in terms of either stage progression or activity levels. Only 6 studies showed a statistically-significant benefit in terms of increased activity. In one study, the control group (who were given 6 months' free gym membership, starting with 3 weeks of supervised exercise instruction) showed a statistically-significant increase in activity levels in comparison with TTM interventions. In the longer term (over 6 months), only 2 out of 7 studies reported some benefit of TTM- based programmes.

TTM-based activity promotion programmes generally found some short-term benefits in terms of activity levels or stage of activity change. Few studies demonstrated any longer term benefits (over 6 months).

The aims of this review were well designed and the searching was reasonably comprehensive, although it would have benefited from the use of other databases (e.g. SPORTDiscus, and EMBASE) and the inclusion of publications in languages other than English. It is possible that some relevant studies have been missed. The authors' use of a narrative discussion was appropriate in view of the types of studies included. The methods of the review, e.g. for extracting the data and assessing the quality of the studies, were not described. As the authors discussed, there were difficulties with losses to follow-up, length of follow-up, and with different approaches to TTM in the included studies.

The authors drew suitably cautious conclusions, highlighted difficulties with this topic, and made sensible suggestions for further research. As the authors discussed, changes in 'stage of change' model for physical activity may not be a good proxy for changes in actual activity levels. It may, therefore, have been more appropriate for the authors' conclusions to have been based on changes in activity levels, rather than a combination of 'stage of change' and activity levels.

Practice: The authors stated that it was unclear whether TTM physical activity promotion was more effective than other non-staged interventions for increasing physical activity, particularly in the longer term.

Research: The authors stated that further studies are needed to assess the benefits of TTM, and made detailed suggestions in relation to study designs.

This is a critical abstract of a systematic review that meets the criteria for inclusion on DARE. Each critical abstract contains a brief summary of the review methods, results and conclusions followed by a detailed critical assessment on the reliability of the review and the conclusions drawn.