Table 1 Adapted STROBE Statement—checklist of items that should be included in reports of observational studies (including additions/adaptations for accommodating geographical data)

Title and abstract

(a) Indicate the study’s design with a commonly used term in the title or the abstract

(b) Provide in the abstract an informative and balanced summary of what was done and what was found

Introduction

Background/rationale

Explain the scientific background and rationale for the investigation being reported

Objectives

State specific objectives, including any prespecified hypotheses

Methods

Study design

Present key elements of study design early in the paper

Setting

Describe the setting, locations, and relevant dates, including periods of recruitment, exposure, follow-up, and data collection

Participants

(a) Cohort study—Give the eligibility criteria, and the sources and methods of selection of participants. Describe methods of follow-up

Case–control study—Give the eligibility criteria, and the sources and methods of case ascertainment and control selection. Give the rationale for the choice of cases and controls

Cross-sectional study—Give the eligibility criteria, and the sources and methods of selection of participants

(b) Cohort study—For matched studies, give matching criteria and number of exposed and unexposed

Case–control study—For matched studies, give matching criteria and the number of controls per case

Variables

Clearly define all geographic variables, outcomes, exposures, predictors, potential confounders, and effect modifiers. Give diagnostic criteria, if applicable

Data sources/ measurement

For each geographic and outcome variable of interest, give sources of data and details of methods of assessment (measurement). Describe comparability of assessment methods if there is more than one group

Bias

Describe any efforts to address potential sources of bias

Study size

Explain how the study size was arrived at

Quantitative variables

Explain how quantitative geographic and outcome variables were handled in the analyses, including how geographic variables were handled in the creation of attribute tables, thematic maps, etc. using GIS software (as well as the name and version number of the software used). If applicable, describe which groupings were chosen and why.

Statistical methods

(a) Describe all statistical methods, including spatial analyses and those used to control for confounding.

(b) Describe any methods used to examine geographic and outcome subgroups and interactions

(c) Explain how missing geographic and outcome data were addressed

(d) Cohort study—If applicable, explain how loss to follow-up was addressed

Case–control study—If applicable, explain how matching of cases and controls was addressed

Cross-sectional study—If applicable, describe analytical methods taking account of sampling strategy

(e) Describe any sensitivity analyses

Results

Participants

(a) Report numbers of individuals at each stage of study—e.g. numbers potentially eligible, examined for eligibility, confirmed eligible, included in the study, completing follow-up, and analysed

(b) Give reasons for non-participation at each stage

(c) Consider use of a flow diagram

Descriptive data

(a) Give characteristics of study participants (e.g. demographic, clinical, social) and information on exposures and potential confounders. Summarize geographic characteristics of study area (if applicable).

(b) Indicate number of participants with missing data for each geographic and outcome variable of interest

(c) Cohort study—Summarise follow-up time (e.g., average and total amount)

Outcome data

Cohort study—Report numbers of outcome events or summary measures over time

Case–control study—Report numbers in each exposure category, or summary measures of exposure

Cross-sectional study—Report numbers of outcome events or summary measures

Main results

(a) Give unadjusted estimates and, if applicable, confounder-adjusted estimates and their precision (e.g., 95% confidence interval). Make clear which confounders were adjusted for and why they were included

(b) Report category boundaries when geographic or continuous outcome variables were categorized

(c) If relevant, consider translating estimates of relative risk into absolute risk for a meaningful time period

Other analyses

Report other analyses done—e.g. spatial analyses, analyses of subgroups and interactions, and sensitivity analyses

Discussion

Key results

Summarise key results with reference to study objectives

Limitations

Discuss limitations of the study, taking into account sources of potential bias or imprecision. Discuss both direction and magnitude of any potential bias

Interpretation

Give a cautious overall interpretation of results considering objectives, limitations, multiplicity of analyses, results from similar studies, and other relevant evidence

Generalisability

Discuss the generalisability (external validity) of the study results

Other information

Funding

Give the source of funding and the role of the funders for the present study and, if applicable, for the original study on which the present article is based