[Show abstract][Hide abstract] ABSTRACT: Food tax-subsidy policies are proposed to hold promise for helping to produce healthier patterns of food purchasing and consumption at population level. Evidence for their effects derives largely from simulation studies that explore the potential effects of untried policies using a mathematical modelling framework. This paper provides a critique first of the nature of the evidence derived from such simulation studies, and second of the challenges of cumulating that evidence to inform public health policy.
Effects estimated by simulation studies of food taxes and subsidies can be expected to diverge in potentially important ways from those that would accrue in practice because these models are simplified, typically static, representations of complex adaptive systems. The level of confidence that can be placed in modelled estimates of effects is correspondingly low, and the level of associated uncertainty is high. Moreover, evidence from food tax-subsidy simulation studies cannot meaningfully be cumulated using currently available quantitative evidence synthesis methods, to reduce uncertainty about effects. Simulation studies are critical for the initial phases of an incremental research process, for drawing together diverse evidence and exploring potential longer-term effects. While simulation studies of food taxes and subsidies provide a valuable and necessary input to the formulation of public health policy in this area, they are unlikely to be sufficient, and policy makers should not place excessive reliance on evidence from such studies, either singly or cumulatively. To reflect known and unknown limitations of the models, results of such studies should be interpreted cautiously as tentative projections. Modelling studies should increasingly be integrated with more empirical studies of the effects of food tax and subsidy policies in practice.
BMC Public Health 12/2015; 15(1):297. DOI:10.1186/s12889-015-1641-5 · 2.26 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Few studies have evaluated the effects of infrastructural improvements to promote walking and cycling. Even fewer have explored how the context and mechanisms of such interventions may interact to produce their outcomes.
This mixed-method analysis forms part of the UK iConnect study, which aims to evaluate new walking and cycling routes at three sites - Cardiff, Kenilworth and Southampton. Applying a complementary follow-up approach, we first identified differences in awareness and patterns of use of the infrastructure in survey data from a cohort of adult residents at baseline in spring 2010 (n = 3516) and again one (n = 1849) and two (n = 1510) years later following completion of the infrastructural projects (Analysis 1). We subsequently analysed data from 17 semi-structured interviews with key informants to understand how the new schemes might influence walking and cycling (Analysis 2a). In parallel, we analysed cohort survey data on environmental perceptions (Analysis 2b). We integrated these two datasets to interpret differences across the sites consistent with a theoretical framework that hypothesised that the schemes would improve connectivity and the social environment.
After two years, 52% of Cardiff respondents reported using the infrastructure compared with 37% in Kenilworth and 22% in Southampton. Patterns of use did not vary substantially between sites. 17% reported using the new infrastructure for transport, compared with 39% for recreation. Environmental perceptions at baseline were generally unfavourable, with the greatest improvements in Cardiff. Qualitative data revealed that all schemes had a recreational focus to varying extents, that the visibility of schemes to local people might be an important mechanism driving use and that the scale and design of the schemes and the contrast they presented with existing infrastructure may have influenced their use.
The dominance of recreational uses may have reflected the specific local goals of some of the projects and the discontinuity of the new infrastructure from a satisfactory network of feeder routes. Greater use in Cardiff may have been driven by the mechanisms of greater visibility and superior design features within the context of an existing environment that was conducive neither to walking or cycling nor to car travel.
International Journal of Behavioral Nutrition and Physical Activity 12/2015; 12(1). DOI:10.1186/s12966-015-0185-5 · 4.11 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Introduction:
Walking and cycling bring health and environmental benefits, but there is little robust evidence that changing the built environment promotes these activities in populations. This study evaluated the effects of new transport infrastructure on active commuting and physical activity.
Quasi-experimental analysis nested within a cohort study.
Four hundred and sixty-nine adult commuters, recruited through a predominantly workplace-based strategy, who lived within 30 kilometers of Cambridge, United Kingdom and worked in areas of the city to be served by the new transport infrastructure.
The Cambridgeshire Guided Busway opened in 2011 and comprised a new bus network and a traffic-free walking and cycling route. Exposure to the intervention was defined using the shortest distance from each participant's home to the busway.
Main outcome measures:
Change in weekly time spent in active commuting between 2009 and 2012, measured by validated 7-day recall instrument. Secondary outcomes were changes in total weekly time spent walking and cycling and in recreational and overall physical activity, measured using the validated Recent Physical Activity Questionnaire. Data were analyzed in 2014.
In multivariable multinomial regression models-adjusted for potential sociodemographic, geographic, health, and workplace confounders; baseline active commuting; and home or work relocation-exposure to the busway was associated with a significantly greater likelihood of an increase in weekly cycle commuting time (relative risk ratio=1.34, 95% CI=1.03, 1.76) and with an increase in overall time spent in active commuting among the least active commuters at baseline (relative risk ratio=1.76, 95% CI=1.16, 2.67). The study found no evidence of changes in recreational or overall physical activity.
Providing new sustainable transport infrastructure was effective in promoting an increase in active commuting. These findings provide new evidence to support reconfiguring transport systems as part of public health improvement strategies.
American journal of preventive medicine 11/2015; DOI:10.1016/j.amepre.2015.09.021 · 4.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Background:
Active commuting may help to increase adults' physical activity levels. However, estimates of its energy cost are derived from a small number of studies which are laboratory-based or use self-reported measures.
Adults working in Cambridge (UK) recruited through a predominantly workplace-based strategy wore combined heart rate and movement sensors and global positioning system (GPS) devices for one week, and completed synchronous day-by-day travel diaries in 2010 and 2011. Commuting journeys were delineated using GPS data, and metabolic intensity (standard metabolic equivalents; MET) was derived and compared between journey types using mixed-effects linear regression.
182 commuting journeys were included in the analysis. Median intensity was 1.28 MET for car journeys; 1.67 MET for bus journeys; 4.61 MET for walking journeys; 6.44 MET for cycling journeys; 1.78 MET for journeys made by car in combination with walking; and 2.21 MET for journeys made by car in combination with cycling. The value for journeys made solely by car was significantly lower than those for all other journey types (p<0.04). On average, 20% of the duration of journeys incorporating any active travel (equating to 8min) was spent in moderate-to-vigorous physical activity (MVPA).
We have demonstrated how GPS and activity data from a free-living sample can be used simultaneously to provide objective estimates of commuting energy expenditure. On average, incorporating walking or cycling into longer journeys provided over half the weekly recommended activity levels from the commute alone. This may be an efficient way of achieving physical activity guidelines and improving population health.
Preventive Medicine 10/2015; In Press. DOI:10.1016/j.ypmed.2015.09.022 · 3.09 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Objective Some studies have assessed the effectiveness of environmental interventions to promote physical activity, but few have examined how such interventions work. We investigated the environmental mechanisms linking an infrastructural intervention with behaviour change.
Design Natural experimental study.
Setting Three UK municipalities (Southampton, Cardiff and Kenilworth).
Participants Adults living within 5 km of new walking and cycling infrastructure.
Intervention Construction or improvement of walking and cycling routes. Exposure to the intervention was defined in terms of residential proximity.
Outcome measures Questionnaires at baseline and 2-year follow-up assessed perceptions of the supportiveness of the environment, use of the new infrastructure, and walking and cycling behaviours. Analysis proceeded via factor analysis of perceptions of the physical environment (step 1) and regression analysis to identify plausible pathways involving physical and social environmental mediators and refine the intervention theory (step 2) to a final path analysis to test the model (step 3).
Results Participants who lived near and used the new routes reported improvements in their perceptions of provision and safety. However, path analysis (step 3, n=967) showed that the effects of the intervention on changes in time spent walking and cycling were largely (90%) explained by a simple causal pathway involving use of the new routes, and other pathways involving changes in environmental cognitions explained only a small proportion of the effect.
Conclusions Physical improvement of the environment itself was the key to the effectiveness of the intervention, and seeking to change people's perceptions may be of limited value. Studies of how interventions lead to population behaviour change should complement those concerned with estimating their effects in supporting valid causal inference.
BMJ Open 09/2015; 5(9):e007593. DOI:10.1136/bmjopen-2015-007593 · 2.27 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The ‘Bikeability’ cycle training scheme, a flagship policy of the government in England, aims to give children the skills and confidence to cycle more safely and more often. Little, however, is known about the scheme׳s reach. This paper examined which schools offer Bikeability, and which children participate in cycle training.
[Show abstract][Hide abstract] ABSTRACT: New transport infrastructure may promote a shift towards active travel, thereby improving population health. The purpose of this study was to determine the effect of a major transport infrastructure project on commuters' mode of travel, trip frequency and distance travelled to work.
Quasi-experimental analysis nested within a cohort study of 470 adults working in Cambridge, UK. The intervention consisted of the opening of a guided busway with a path for walking and cycling in 2011. Exposure to the intervention was defined as the negative of the square root of the shortest distance from home to busway. The outcome measures were changes in commute mode share and number of commute trips - both based on a seven-day travel-to-work record collected before (2009) and after (2012) the intervention - and change in objective commute distance. The mode share outcomes were changes in the proportions of trips (i) involving any active travel, (ii) involving any public transport, and (iii) made entirely by car. Separate multinomial regression models were estimated adjusting for commute and sociodemographic characteristics, residential settlement size and life events.
Proximity to the busway predicted an increased likelihood of a large (>30 %) increase in the share of commute trips involving any active travel (relative risk ratio [RRR] 1.80, 95 % CI 1.27, 2.55) and a large decrease in the share of trips made entirely by car (RRR 2.09, 95 % CI 1.35, 3.21), as well as a lower likelihood of a small (<30 %) reduction in the share of trips involving any active travel (RRR 0.47, 95 % CI 0.28, 0.81). It was not associated with changes in the share of commute trips involving any public transport, the number of commute trips, or commute distance.
The new infrastructure promoted an increase in the share of commuting trips involving active travel and a decrease in the share made entirely by car. Further analysis will show the extent to which the changes in commute mode share were translated into an increase in time spent in active commuting and consequent health gain.
International Journal of Behavioral Nutrition and Physical Activity 06/2015; 12(1):81. DOI:10.1186/s12966-015-0239-8 · 4.11 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Changes to the environment that support active travel have the potential to increase population physical activity. The Cambridgeshire Guided Busway is an example of such an intervention that provides new traffic-free infrastructure for walking, cycling and public transport. This qualitative investigation explored the diverse experiences of new transport infrastructure and its impacts on active travel behaviours.
Thirty-eight adult participants from the Commuting and Health in Cambridge natural experimental study were purposively selected according to their demographic and travel behaviour change characteristics and invited to participate in semi-structured interviews between February and June 2013. A mixed-method, following-a-thread approach was used to construct two contrasting vignettes (stories) to which the participants were asked to respond as part of the interviews. Inductive thematic qualitative analysis of the interview data was performed with the aid of QSR NVivo8.
Perceptions of the busway's attributes were important in shaping responses to it. Some participants rarely considered the new transport infrastructure or described it as unappealing because of its inaccessibility or inconvenient routing. Others located more conveniently for access points experienced the new infrastructure as an attractive travel option. Likewise, the guided buses and adjacent path presented ambiguous spaces which were received in different ways, depending on travel preferences. While new features such as on board internet access or off-road cycling were appreciated, shortcomings such as overcrowded buses or a lack of path lighting were barriers to use. The process of adapting to the environmental change was discussed in terms of planning and trialling new behaviours. The establishment of the busway in commuting patterns appeared to be influenced by whether the anticipated benefits of change were realised.
This study examined the diverse responses to an environmental intervention that may help to explain small or conflicting aggregate effects in quantitative outcome evaluation studies. Place and space features, including accessibility, convenience, pleasantness and safety relative to the alternative options were important for the acceptance of the busway. Our findings show how environmental change supporting active travel and public transport can encourage behaviour change for some people in certain circumstances.
International Journal of Behavioral Nutrition and Physical Activity 06/2015; 12(1):72. DOI:10.1186/s12966-015-0230-4 · 4.11 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Active commuting is associated with various health benefits, but little is known about its causal relationship with body mass index (BMI).
We used cohort data from three consecutive annual waves of the British Household Panel Survey, a longitudinal study of nationally representative households, in 2004/2005 (n=15 791), 2005/2006 and 2006/2007. Participants selected for the analyses (n=4056) reported their usual main mode of travel to work at each time point. Self-reported height and weight were used to derive BMI at baseline and after 2 years. Multivariable linear regression analyses were used to assess associations between switching to and from active modes of travel (over 1 and 2 years) and change in BMI (over 2 years) and to assess dose-response relationships.
After adjustment for socioeconomic and health-related covariates, the first analysis (n=3269) showed that switching from private motor transport to active travel or public transport (n=179) was associated with a significant reduction in BMI compared with continued private motor vehicle use (n=3090; -0.32 kg/m(2), 95% CI -0.60 to -0.05). Larger adjusted effect sizes were associated with switching to active travel (n=109; -0.45 kg/m(2), -0.78 to -0.11), particularly among those who switched within the first year and those with the longest journeys. The second analysis (n=787) showed that switching from active travel or public transport to private motor transport was associated with a significant increase in BMI (0.34 kg/m(2), 0.05 to 0.64).
Interventions to enable commuters to switch from private motor transport to more active modes of travel could contribute to reducing population mean BMI.
Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.
Journal of epidemiology and community health 05/2015; 69(8). DOI:10.1136/jech-2014-205211 · 3.50 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We examined the impact of regulatory action to reduce levels of artificial trans-fatty acids (TFAs) in food. We searched Medline, Embase, ISI Web of Knowledge, and EconLit (January 1980 to December 2012) for studies related to government regulation of food- or diet-related health behaviors from which we extracted the subsample of legislative initiatives to reduce artificial TFAs in food. We screened 38 162 articles and identified 14 studies that examined artificial TFA controls limiting permitted levels or mandating labeling. These measures achieved good compliance, with evidence of appropriate reformulation. Regulations grounded on maximum limits and mandated labeling can lead to reductions in actual and reported TFAs in food and appear to encourage food producers to reformulate their products. (Am J Public Health. Published online ahead of print January 20, 2015: e1-e11. doi:10.2105/AJPH.2014.302372).
American Journal of Public Health 01/2015; 105(3):e1-e11. DOI:10.2105/AJPH.2014.302372 · 4.55 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: New transport infrastructure may help promote active travel, thereby contributing to increasing overall physical activity and population health gain. In 2011 a guided busway with a path for walking and cycling was opened in Cambridgeshire, UK. This paper investigates the predictors of walking, cycling and bus use on the busway.
Cross-sectional analyses of the final questionnaire wave (2012) of the Commuting and Health in Cambridge cohort study following the opening of the busway. Participants were 453 adult commuters who had not moved home or workplace. Busway use was self-reported and proximity calculated using GIS. Separate multivariable logistic regression models were used to assess predictors of walking, cycling and bus use on the busway.
Exposure to the intervention (proximity: the negative square root of the distance from home to busway in kilometres) increased the odds of use for cycling (OR 2.18; 95% CI 1.58 to 3.00), bus travel (OR 1.53, 95% CI 1.15 to 2.02) and walking (OR 1.34; 95% CI 1.05 to 1.70). The effect of exposure was strengthened in towns for bus use, and in towns and villages for walking, compared with urban areas. Men were more likely than women to have cycled on the busway, whereas individual socioeconomic characteristics did not predict bus use or walking.
New high-quality transport infrastructure attracts users, determined by geographical exposure and spatial contextual factors such as settlement size and availability of parking at work. Future longitudinal analyses will determine effects on overall travel and physical activity behaviour change.
[Show abstract][Hide abstract] ABSTRACT: Several jurisdictions are now imposing taxes on food and beverages to prevent obesity (and related conditions). Existing evidence concerning their effects comes largely from simulation studies and trials in closed settings, both of which have limitations. Rigorous evaluation of actual taxes may provide richer evidence with greater external validity to support policy making. This article describes existing evaluation studies and outlines an implicit underlying theoretical framework for how taxes are expected to affect health. It then explores three important issues for future studies: selection of an appropriate evaluative perspective (comparing realist and biomedical experimental paradigms); approaches to causal inference; and the challenge of a low signal-to-noise ratio. We argue that evaluation should be informed by a realist perspective as well as making appropriate use of established empirical quasi-experimental approaches to testing causal effects. This should be underpinned by a theoretical framework that acknowledges complexity and the potential diversity of impacts.
[Show abstract][Hide abstract] ABSTRACT: Background
Existing reviews identify numerous studies of the relationship between urban built environment characteristics and obesity. These reviews do not generally distinguish between cross-sectional observational studies using single equation analytical techniques and other studies that may support more robust causal inferences. More advanced analytical techniques, including the use of instrumental variables and regression discontinuity designs, can help mitigate biases that arise from differences in observable and unobservable characteristics between intervention and control groups, and may represent a realistic alternative to scarcely-used randomised experiments. This review sought first to identify, and second to compare the results of analyses from, studies using more advanced analytical techniques or study designs.Methods
In March 2013, studies of the relationship between urban built environment characteristics and obesity were identified that incorporated (i) more advanced analytical techniques specified in recent UK Medical Research Council guidance on evaluating natural experiments, or (ii) other relevant methodological approaches including randomised experiments, structural equation modelling or fixed effects panel data analysis.ResultsTwo randomised experimental studies and twelve observational studies were identified. Within-study comparisons of results, where authors had undertaken at least two analyses using different techniques, indicated that effect sizes were often critically affected by the method employed, and did not support the commonly held view that cross-sectional, single equation analyses systematically overestimate the strength of association.Conclusions
Overall, the use of more advanced methods of analysis does not appear necessarily to undermine the observed strength of association between urban built environment characteristics and obesity when compared to more commonly-used cross-sectional, single equation analyses. Given observed differences in the results of studies using different techniques, further consideration should be given to how evidence gathered from studies using different analytical approaches is appraised, compared and aggregated in evidence synthesis.
International Journal of Behavioral Nutrition and Physical Activity 11/2014; 11(1):142. DOI:10.1186/s12966-014-0142-8 · 4.11 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: 276 GPS-tracked commute trips from a free-living sample of adults were analysed.•GPS routes were compared with GIS-modelled shortest routes.•GIS may be acceptable for distance estimation for active commuting.•GPS should be used to obtain accurate estimates of environmental contexts.•Method chosen will likely influence conclusions on health implications of commuting.
[Show abstract][Hide abstract] ABSTRACT: Objective
To assess associations between changes in perceptions of the environment en route to work and changes in active commuting.
655 commuters in Cambridge, UK reported perceptions of their commuting route and past-week commuting trips in postal questionnaires in 2009 and 2010. Associations between changes in route perceptions and changes in time spent walking and cycling, proportion of car trips, and switching to or from the car on the commute were modelled using multivariable regression.
Changes in only a few perceptions were associated with changes in travel behaviour. Commuters who reported that it became less pleasant to walk recorded a 6% (95% CI: 1, 11) net increase in car trips and a 12 min/week (95% CI: − 1, − 24) net decrease in walking. Increases in the perceived danger of cycling or of crossing the road were also associated with increases in car trips. Increases in the perceived convenience of public transport (OR: 3.31, 95% CI: 1.27, 8.63) or safety of cycling (OR: 3.70, 95% CI: 1.44, 9.50) were associated with taking up alternatives to the car.
Interventions to improve the safety of routes and convenience of public transport may help promote active commuting and should be evaluated.
Preventive Medicine 10/2014; 67. DOI:10.1016/j.ypmed.2014.06.033 · 3.09 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The planning profession has been advocated as an untapped resource for obesity prevention, but little is known about how planners view their roles and responsibilities in this area. This paper investigates the role of planners in the Healthy Towns programme in England, and explores the limits and potential for obesity prevention within planning policy and practice. Using a qualitative approach, 23 planning stakeholders were interviewed, identifying the potential for planning in public health, particularly the ‘health proofing’ of local planning policy. National and local governments should better align planning and health policies to support collaboration between planners and public health practitioners.
Health & Place 09/2014; 30:120–126. DOI:10.1016/j.healthplace.2014.08.012 · 2.81 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Active commuting may make an important contribution to population health. Accurate measures of these behaviours are required, but it is unknown how self-reported estimates compare to those derived from objective measures. We sought to develop methods for objectively deriving time spent in specific travel behaviours from a combination of locational and activity data, and to assess the convergent validity of two self-reported estimates.
In 2010 and 2011, a sub-sample of participants from the Commuting and Health in Cambridge study concurrently completed objective monitoring using combined heart rate and movement sensors and global positioning system devices and reported their past-week commuting in a questionnaire (modes used, and usual time spent walking and cycling per trip) and in a day-by-day diary (all modes and durations). Automated and manual approaches were used to objectively identify total time spent using active and motorised modes. Agreement between self-reported and objectively-derived times was assessed using Lin’s concordance coefficients, Bland-Altman plots and signed-rank tests.
Compared to objective assessments, day-by-day diary estimates of time spent using active modes on the commute were overestimated by a mean of 1.1 minutes/trip (95% limits of agreement (LOA): −7.7 to 9.9, p < 0.001). The magnitude of overestimation was slightly larger, but not significant (p = 0.247), when walking or cycling was used alone (mean: 2.4 minutes/trip, 95% LOA: −6.8 to 11.5). Total time spent on the commute was overestimated by a mean of 1.9 minutes/trip (95% LOA: −15.3 to 19.0, p < 0.001). The mean differences between self-reported usual time and objective estimates were −1.1 minutes/trip (95% LOA: −8.7 to 6.4) for cycling and +2.4 minutes/trip (95% LOA: −10.9 to 15.7) for walking. Mean differences between usual and daily estimates of time were <1 minute/trip for both walking and cycling.
We developed a novel method of combining objective data to identify time spent using active and motorised modes, and total time spent commuting. Compared to objectively-derived times, self-reported times spent active commuting were slightly overestimated with wide LOA, suggesting that they should be used with caution to infer aggregate weekly quantities of activity on the commute at the individual level.
International Journal of Behavioral Nutrition and Physical Activity 09/2014; 11(1):116. DOI:10.1186/s12966-014-0116-x · 4.11 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Background
No current validated survey instrument allows a comprehensive assessment of both physical activity and travel behaviours for use in interdisciplinary research on walking and cycling. This study reports on the test-retest reliability and validity of physical activity measures in the transport and physical activity questionnaire (TPAQ).
The TPAQ assesses time spent in different domains of physical activity and using different modes of transport for five journey purposes. Test-retest reliability of eight physical activity summary variables was assessed using intra-class correlation coefficients (ICC) and Kappa scores for continuous and categorical variables respectively. In a separate study, the validity of three survey-reported physical activity summary variables was assessed by computing Spearman correlation coefficients using accelerometer-derived reference measures. The Bland-Altman technique was used to determine the absolute validity of survey-reported time spent in moderate-to-vigorous physical activity (MVPA).
In the reliability study, ICC for time spent in different domains of physical activity ranged from fair to substantial for walking for transport (ICC = 0.59), cycling for transport (ICC = 0.61), walking for recreation (ICC = 0.48), cycling for recreation (ICC = 0.35), moderate leisure-time physical activity (ICC = 0.47), vigorous leisure-time physical activity (ICC = 0.63), and total physical activity (ICC = 0.56). The proportion of participants estimated to meet physical activity guidelines showed acceptable reliability (k = 0.60). In the validity study, comparison of survey-reported and accelerometer-derived time spent in physical activity showed strong agreement for vigorous physical activity (r = 0.72, p<0.001), fair but non-significant agreement for moderate physical activity (r = 0.24, p = 0.09) and fair agreement for MVPA (r = 0.27, p = 0.05). Bland-Altman analysis showed a mean overestimation of MVPA of 87.6 min/week (p = 0.02) (95% limits of agreement −447.1 to +622.3 min/week).
The TPAQ provides a more comprehensive assessment of physical activity and travel behaviours and may be suitable for wider use. Its physical activity summary measures have comparable reliability and validity to those of similar existing questionnaires.
PLoS ONE 09/2014; 9(9):e107039. DOI:10.1371/journal.pone.0107039 · 3.23 Impact Factor