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Dear Editor,
Sub: Resubmission of the manuscript, "Urban built environment configuration and psychological
distress in older men: Results from the Caerphilly study" (MS: 1233798701695374)
Please find attached the modified draft of our article "Urban built environment configuration and
psychological distress in older men: Results from the Caerphilly study". We are grateful for the
opportunity to extensively revise the article and thank the reviewers for their helpful and insightful
comments. We have set out our response below, addressing each comment in turn, highlighting the
changes made to the article as well as the rationale.
We hope the revised article meets the standards for publication in BMC Public Health and look
forward to hearing from you.
Yours faithfully,
Chris Webster BSc DipTP MSc PhD DSc(econ) FRSA AcSS NTF
Head of School
Professor of Urban Planning and Development
Cardiff School of Planning and Geography
Cardiff University
Glamorgan Building
King Edward VII Avenue
Cardiff CF10 3WA
Wales, UK
Tel +44(0)20 20876084
Response to Reviewer 1
Abstract
1. What is a ‘Lower Layer Super Output Area’: is this a proxy neighbourhood?
Response: Lower super output areas are small area geographies defined by UK Office of National
Statistics with a reasonable degrees of homogeneity in shape and social composition. To help
the reader we have defined LSOA as ‘neighbourhood’ in the text. We have taken the LSOAs as
level 2 neighbourhoods in our multi-level analyses. This is clarified in the methods section.
2. What does the association with slope variability indicate: can the direction of the association be
indicated (e.g. hillier areas were more conducive to better psychological health)
Response: We hypothesise that variability in slope has an impact upon physical activity patterns
rather than slope per se. Therefore, rather than measuring average or spot slope, the study
measured slope variability, parameterized as one standard deviation in slope within a kilometre
network buffer around a respondent's dwelling. In our study, hillier areas that correspond to
higher slope variability were associated with poorer psychological health. This has been clarified
in the abstract and paper.
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3. The Abstract should make it clear that despite the CaPS being prospective, the analysis for this
present study (5th wave) is cross-sectional.
Response: The word cross sectional has now been added to the Abstract
4. The Abstract (and possibly the title) should make it clear that the CaPS study is based on males
only
Response: We have modified the title and abstract accordingly.
Background
5. Can the authors please clarify the seeming contradiction between the first and last sentences of
paragraph 1 on page 4: the first indicates “several studies” and the last indicates “virtually no
study”? Maybe the difference is due to the authors’ use of the terms “built environment
characteristics” (first sentence) and “built environment configuration” (last sentence). Are the
authors referring to two different literatures/concepts? In which case, can this be clarified and
made more explicit.
Response: Thank you for this particularly helpful comment. We have now clarified the text.
6. As part of the Background I would have liked to have seen greater conceptual development of
the proposed relationships. Why for example would we expect the street-network to be
associated with psychological health (PH)? Is it because greater street connectivity facilitates less
restricted access through the neighbourhood, thus fostering social ties and interactions, leading
to better PH? Explicit “theoretical” statements of this type would help the readers’ appreciation
of the issues being examined and more clearly highlight the “so what” factor of the study.
Similarly, why, and in what ways might we expect the neighbourhood environment and
neighbourhood deprivation to moderate the association between the built environment and
PH? At present, this aspect of the study is noted (almost in passing) in the last sentence of the
background.
Response: We have modified the Background section with an explicit mention of hypothesese.
7. Page 6. I would caution the authors to think critically about their use of a modelling approach
that includes so many (so-called) confounders. If any of the confounders are actually mediators
of the association between the built environment and PH then adjustment for the confounder
will inappropriately explain variation that was more appropriately attributable to the built
environment, hence underestimating the actual impact of the built environment on PH. In
specifying (and ideally simplifying) their models I would encourage the authors to consider the
approach described by Fleischer and Diez Roux in their paper “Using Direct Acyclic Graphs to
Guide Analysis of Neighbourhood health effects”, Journal of Epidemiology and Community
Health 2008;62(9):842-6.
Response: Again, we thank the reviewer for raising this issue. The use of DAGS in making these
decisions is an exciting development, but one which is hypothesis specific. We did not consider
our hypotheses to be sufficiently specific for a DAGs based analysis to be appropriate.
Nevertheless, appropriate statistical adjustment is a knotty problem. For example should the
strategy be only to consider variables for which there are statistically significant associations in
the dataset, or variables with established associations in other datasets or variables with a good
theoretical basis for inclusion? Originally, our approach was very conservative and we
attempted to nullify the associations by including many confounders. However, we agree that
this reduces the power for the analysis and we have now reduced the number of variables to 5
variables. Age has been included as a standard covariate, and the remainder (alcohol, social
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class, education and vascular disease) included as there was some evidence of an association
with mental health.
Methods
8. Page 7. The text on this page (and the next) describes the presumed links between the built
environment and PH. To me at least this type of material represents an important conceptual
and theoretical basis for the study and would therefore be better placed in the Background
rather than the Methods (and measurement) section.
Response: Agreed. The material has been moved as suggested.
9. Figure 1 was too small to be able to clearly discern the different spatial scales described by the
authors. If published, I’d recommend that a much larger image be included.
Response: We have enlarged Figure 1 so as to make it more discernible.
10. Apologies if I missed it earlier in the paper, but my first encounter with the acronym LSOA was
on page 9. After searching back to the Abstract I worked out that this referred to “Lower Super
Output Areas’. However, knowing this left me none the wiser as it was unclear what an LSOA
actually was. Can this please be explained at an appropriate point in the manuscript?
Response: Thank you for spotting this oversight. Lower Super Output Areas (LSOA) have now
been described in detail on page 8 under Area level deprivation with appropriate references.
11. Can the authors please justify a cut-point of #5 on the GHQ-30 as indicating psychological
distress? Has this cut-point been used previously in published research, and if so, can an
appropriate source be cited?
Response: The cut point for GHQ 30 employed here is the standard one as recommended by the
test authors’. This criterion has also been validated in the CaPS cohorts (Stansfeld SA, Gallacher
JEJ, Sharp DS, et al. Psychol Med 1991;21: 157–67). This has been clarified in the text.
12. Did the preliminary model testing justify the inherent linear assumptions associated with
including age and alcohol consumption as continuous variables?
Response: Due to the narrow age range of the cohort a curvilinear relationship with mental
health was not expected and this was confirmed. For alcohol consumption, teetotallers had a
slightly greater risk of poor mental health than light drinkers. However, the association along the
range from light to heavy drinkers was linear. It was decided that for the purposes of adjusting
for confounding there would have been no net gain by categorising alcohol consumption and
thereby losing information.
13. 13. Can the authors indicate in the manuscript if the measures of vascular morbidity were selfreported or clinically assessed?
Response: The measures of vascular morbidity were clinically assessed, although angina, by
definition, is diagnosed from symptoms.
14. Can more information be provided about how the 5th wave of the CaPS sample differed from
baseline? What was the response rate for the 5th and previous waves? Presumably the loss to
follow-up was non-random and the sample became more homogenous over-time, resulting in
less within-sample variation. What might have been the implications of wave attrition for the
study’s findings and subsequent conclusions?
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Response: The response rate has been between 85% and 90% at each wave. However, there has
been remarkably little loss of heterogeneity with the full range of values of risk factors
continuing to be represented in the cohort. The issue of representativeness is helpful for the
purposes of applying scientific knowledge but it is not essential for identifying generalisable
associations.
15. What is meant by the phrase “representative sample” (page 11, first paragraph, and then again
on page 12, first paragraph of the Discussion)? In what sense, and of whom, is the sample
representative, and can evidence (e.g. previous published research) be cited to support this
statement?
Response: The term is used here to describe a community sample that was selected to be
representative of men in Caerphilly borough aged 45-59 at recruitment. The significance of this
term however, is to help the reader characterise the population sample being assessed.
16. It is now strongly recommended that Markov chain Monte Carlo simulation be used with
multilevel logistic models, especially as in the present case with small-to-moderate sized
samples, and when estimating variances (in this case the LSOA random effects). In light of this,
can the authors provide a justificationfor the use of GLAMM, which uses adaptive quadrature?
Response: We have now redone the analyses employing MCMC simulation by using the
runmlwin command within Stata. This enabled us to fit multi-level models employing the MCMC
method with MLWin.
17. Why didn’t the authors describe the findings for Table 4? Instead, they simply referred the
reader to the Table on the last line of the findings section.
Response: We have now modified our tables. Our findings of logistic mixed effects models have
been presented in the composite Table 3 with a discussion of results in the findings section.
18. For this reviewer at least, the findings of the study, and the authors subsequent interpretation of
them (especially the surprising and inconsistent results) are a little clouded by the large number
of confounders included in some of the models. I did wonder about the “thinness” (stability) of a
logistic model with only 133 cases in the numerator being predicted by such a large number of
variables, as large models with modest sample-sizes substantially reduces statistical power and
can produce unreliable findings.
Response: As described above (point 7) we have reduced the number of covariates. Five key
individual level confounders have now been included in all our models (age, alcohol
consumption, social class, education and prevalence of vascular morbidities) instead of twelve in
our initial analysis.
19. Page 16. I don’t concur with the authors that the use of residents’ perceptions is a limitation or
weakness: it is simply a different but nevertheless important factor influencing how people use
their neighbourhood.
Response: We have now omitted the mention of this view so as to remove any ambiguity on this
topic.
20. Throughout the Discussion it would have been good to see greater mention of the implications
of the study’s findings for public policy, urban design, town planning, and other disciplines
involved in the development of neighbourhoods that support and promote health and wellbeing, both physical and mental.
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Response: We agree with the reviewer regarding the importance of applying findings. In the
concluding paragraph of the paper we have tried to stress that our study presents a detailed
analysis of built environment which has potential towards optimizing urban planning and design
at a community level so as to devise effective intervention strategies in preventive health.
General implications have been mentioned. At the same time we have refrained from being
overly specific about planning implications stressing the point that future large-scale studies are
needed for gathering further evidence.
Response to Reviewer 2's Report
This is an interesting manuscript providing new valuable evidence. There is a need for additional
referencing and reorganisation of the sections. The addition of a comparison between Frank’s
connectivity and Space Syntax would strengthen the results of this paper. I have sometimes
repeated revision information within several of the BMC’s points for consideration. This manuscript
will be of a good quality for publication after revision.
Response: In addressing the reviewer’s points we have interpreted the revision request to be
referring to the comments in the subsequent paragraph.
1. Is the question posed by the authors well defined?
The question posed by the authors is well defined. The introduction states that there have been few
studies examining this topic, which nicely indicates this manuscript will be examining the same topic.
The space syntax history and theory is introduced before natural environment variables are also
mentioned. These introductions and the main hypothesis are explicitly stated.
Major Compulsory Revision
However, there is insufficient background material and references within the background. Instead
these are found within the methods section and this seems to have created omissions of references.
There are several unsubstantiated claims that have no precedence. I realise that you may have
found novel results, however general background material supporting the hypotheses, seem to be
somewhat lacking due to the incorrect organisation of the methods section.
Response: We have reorganized the materials in the Background and Methods sections as per
Referee's suggestions. The Background includes an explicit mention of the study hypothesis with
references.
2. Are the methods appropriate and well described?
Minor Essential Revision
I am not a statistician; however from my experience I find the statistical methods, including
multilevel modelling, to be appropriate. I question the use of both the full table (Table 3) and repeat
of the significant statistics within the text. A list of the non-significant variables would be more
efficient, thereby leaving a clearer table with only the significant variables. This would remove the
need to repeat the few significant variables within the text and increase reader legibility. The
“cleaner” table will appear close to the text describing the results in a published paper.
Response: The reviewer raises two points. Regarding the efficiency of the table 3, we do not
consider formal levels of statistical significance to be particularly informative and so have preferred
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to provide confidence limits for all variables and allow the reader to judge on the strength of
evidence for an association. Regarding the repetition of findings in the text, our desire is to make the
findings as accessible as possible to the reader.
Major Compulsory Revision
The GIS methods have not been described in sufficient detail to allow other readers to repeat this
study. The work of Larry Frank and others’, which the authors cite, provides enough evidence to
begin to recreate their work. The authors of the current paper could rely on previous published work
to some extent but additional detail should be provided within the manuscript.
Response: In compliance with the Reviewer's advice, we have now reinforced our Methods section.
Technical details of spatial analysis, employed land use mix formulae and space syntax based street
network analysis have now been included.
Major Compulsory Revision
Some of the methods section is not methods. For example, hypotheses about “proper land use
planning with optimised mix and density of attractive destinations would have a positive effect on
psychological health….” Belong either in background, or discussion, but not in methods section. The
discussion of hypotheses within the methods section may have hampered the style and reduced
space for technical detail that should have been included.
Response: We have now reorganized the materials in the Background and Methods sections as per
Referee's suggestions.
Major Compulsory Revision
Within the methods section, street-level accessibility is discussed instead of the method being
described in sufficient detail. The high street choice metrics are stated as being measured at 800 m
radius. However, the results in Table 2 give results for Choice R1200m. The comparison with SS
methods and connectivity could also be extended to explore the different “choice distances”.
References to justify the use of 800 m distance (or 1200 m) should be included.
Response: The oversight has now been corrected. In our network model, we have considered a
radius of 1200 metres for the calculation of local movement potential; a standard criterion 15
minutes stroll. Given the spatial extent of Caerphilly, a radius of 3000 metres was employed for the
calculation of city level movement potential. Global accessibility was operationalized by considering
all the network segments in our model (referred in technical terms as movement potential at radius
N).
The superiority of space syntax models stem from their ability to assess the impact of accessibility at
multiple spatial scales. This has now been mentioned in the Discussion section.
Minor Essential Revision
Readers who are familiar with Larry Frank’s work, but not with Space Syntax, may be somewhat
misdirected with mention of Frank’s research. Although land use density measure is used within the
current paper, there is no mention of Frank’s connectivity measure. The reader is then left
wondering why Space Syntax has been chosen over connectivity. The author’s should consider a
comparison between Frank’s connectivity and Space Syntax. I think the SS method will be new to
many BMC PH readers and the origins of this method should be returned to again in the discussion
to explain the rationale behind it.
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Response: The concept of space syntax has been described in greater detail. An introduction to
space syntax based network modelling and its operationalization in our study has been mentioned in
the Methods Discussion section. Previously street connectivity has been employed in many studies
which enumerated the density of street intersections within a defined buffer. Space syntax is a
network modelling technique which enables a more detailed assessment of street configuration at
multiple urban scales and hence, have been employed in the present study. The movement potential
of a street segment simulates counts of movements through a segment within defined urban scales.
Street network accessibility may act as a predictor of movement as well as define actual use of
community resources. At a radius of walkable distance, this may act as proxy of physical activity and
social connectivity whereas, at a global scale, it correlates with traffic density, road safety, and
pollution which may act as inhibitors to healthy living. As per the Referee's advice, these points have
now been mentioned in the Discussion section.
Minor Essential Revision
Physical activity is mentioned on page 7, the second paragraph on the built environment. However,
this is the first time it is mentioned and again, this is the methods section. The way it is written
suggests they have measures of activity they are using in this analysis. This does not seem to be the
case and is therefore misleading. If activity is mentioned this should be in the discussion, otherwise
readers will expect activity data to form part of the analysis.
Response: This has now been removed from the Methods section, while the preventive role played
by physical activity in influencing mental health have been mentioned in the Background section as a
part of the hypothesis.
3. Are the data sound?
It is difficult to comment on the soundness of the GIS data because methods describing their
derivation have insufficient detail, as described above.
Major Compulsory Revision
A direct comparison between connectivity and Space Syntax is something the authors should
consider adding to strengthen their manuscript.
Response: This has now been incorporated in the Discussion section.
Major Compulsory Revision
I am somewhat concerned that the built environment domain of WIMD has been included as an area
level measure when the study is specifically exploring the environment. This may have led to
circularity and the finding of significant results when there are none. The mental health data and
other health data are sound and based on a well-established cohort.
Response: As suggested by the Reviewer, we have now redone the analysis by including six of the
seven domains of the Welsh Index of Multiple deprivation. The accessibility to services domain has
been excluded from our models in order to overcome any multi-collinearity.
4. Does the manuscript adhere to the relevant standards for reporting and data deposition?
Yes, the statistical analysis is reported using odds ratios, confidence interval and p-values, as
appropriate. Units are standard metric.
Minor Essential Revision
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Authors may need to add an Ordnance Survey acknowledgement directly on the map (Fig 1). They
have derived data but it is based on the ITN OSMM layer.
Response: As per the reviewer's comment, we have now added captions to Figure 1 as well as
mentioned this in the subject to reflect that space syntax analysis was conducted over the network
data derived from ITN OSMM layer.
5. Are the discussion and conclusions well balanced and adequately supported by the data?
The discussion is well written and interesting. The discussion should be expanded to incorporate the
points I have made earlier in the review.
Response: The discussion has been re-modified to comply with the Referee's advice.
Minor Essential Revision
Although it is possible to work out what the author’s mean, the last sentence of first paragraph in
the discussion (attenuated after adjustments for natural environment), and that of the second
paragraph (all the more relevant given that Caerphilly), would benefit with further explanation to
make reading the manuscript easier.
6. Are limitations of the work clearly stated?
Minor Essential Revision
The authors have described several limitations. The year of the Ordnance Survey MasterMap data is
not given; the mismatch between this and the study data could be a limitation, it is unknown.
Response: Limitations arising out of temporal mismatch over the period of CaPS phase V survey has
now been acknowledged in the Strengths and Limitations section.
7. Do the authors clearly acknowledge any work upon which they are building, both published and
unpublished?
Major Compulsory Revision
Largely this has been completed, however the hypotheses (currently in the methods) have not been
adequately referenced.
Response: We have now re-organized the Background and Methods section of the paper along with
addition of appropriate references.
8. Do the title and abstract accurately convey what has been found?
The title and abstract accurately convey the study results clearly without overstating.
9. Is the writing acceptable?
The writing is at an acceptable standard. The manuscript would benefit from a grammar check, and
there is a certain amount of reorganisation recommended due to several hypotheses and
background material present in methods section.
(Major Essential Revision)
Minor Essential Revision
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Please alter spelling to Ordnance Survey. The OSMM layers described are product names and should
be capitalised appropriately.
Response: We have incorporated the reorganization suggested. We have now corrected the spelling
errors.
Minor Essential Revision
It is the Welsh Index of Multiple Deprivation.
Response: The oversight has now been corrected.