Table 3 Results - observational studies identified in Stage 2 that used alternative study designs or methodological approaches to support causal inference (n = 6)
Study details | Description of variables | Results (for two different methods of analysis, when reported) | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Independent variables | Dependent variables | Main method of analysis: | Alternative method of analysis: | |||||||||
Panel data, RCT or SEM | Cross-sectional analysis | |||||||||||
First author, date, journal | Study population | Description | Time varying | Areal unit | Description | Source | Description of study design | Data type (time periods) | Effect sizes (95% confidence interval)1 | Method | Effect sizes (95% confidence interval)1 | |
Results where no statistically significant differences are observed between main and alternative analyses | Results where a mismatch between results is observed2 | |||||||||||
Franzini, 2009, Am J Public Health [39] | U.S. children (all States; 10-12 year olds) | Traffic levels, physical disorder, residential density and land use | N/A | Individual Systemic Social Observations | BMI | Interviews with students and their parents, 2003 | Structural equation modelling (SEM) | Cross sectional (1) | 0.03 (-0.40, 0.46) (these results relate to physical activity z-scores which contributed to the SEM. Physical environment had no significant impact on physical activity or BMI in the model) | Not reported | ||
Gibson, 2011 [40], Am J Public Health | U.S. young people (all States) | Five measures relating to food environment, including: | No | Zip-code level | BMI (obesity likelihood was also reported) | NLSY, 1998-2004 | Fixed effects panel data analysis | Longitudinal data (2) | Change in BMI: | OLS | None | Under-estimates: |
(a.) supermarkets per square mile | (a.) -1.98* (-1.94,-2.02) | (a.) -0.04 (-0.18, 0.10) | ||||||||||
(b.) small grocery stores, and per square mile | (b.) -0.15* (-0.33,0.04) | (b.) 0.02 (-0.00, 0.04) | ||||||||||
(c.) full-service restaurants per square mile | (c.) 0.20* (0.03, 0.36) | (c.) -0.00 (-0.01, 0.01) | ||||||||||
Kapinos, 2011 [38], Journal of Adolescent Health | U.S. undergraduate students (a single university campus) | Characteristics of dormitory accommodation: | No | Specific to the location of the dormitory accommodation | Weight (kg) (other outcome relating to exercise frequency, meals and snacks are not reported here) | Individual-level survey instrument (39 questions) | Randomised experiment (undergraduates were randomised to different dormitory accommodation) | Cohort data (2) One-year follow-up | Male (M) and female (F) participants: | Not reported | ||
(a.) on-site dining hall | (a.) M: 0.19 (-2.37, 2.76) F: 0.85* (0.12, 1.57) | |||||||||||
(b.) distance to gym | (b.) M: -0.25 (-1.37, 0.87) F: 0.13 (-0.32, 0.59) | |||||||||||
(c.) distance to central campus | (c.) M: -0.08 (-0.80, 0.63) F: -0.45 (-1.15, 0.25) | |||||||||||
Kling, 2004, National Bureau of Economic Research [37] | U.S. (five cities; families with children; 85% with African-American or Hispanic female as household head) | Moving from a high poverty (public housing area) to a low poverty (a census tract with a poverty rate of less than ten percent) neighbourhood | No | Poverty rate was measured at the census tract level | Obesity likelihood | Individual-level survey | Randomised experiment: (moving to low poverty areas) | Cohort data (2) Five-year follow-up | (a.) intent-to-treat effect i.e. effect of being offered a housing voucher or the average effect of an attempted policy intervention on the entire target population: | Not reported | ||
-0.048* (-0.091, -0.005) | ||||||||||||
(b.) treatment-on-treated i.e. those who moved using voucher | ||||||||||||
-0.103* (-0.195, -0.011) | ||||||||||||
Powell, 2009, Journal of Health Economics [41] | U.S. young people (all States) | Measures included: | No | County level | BMI | NLSY, 1997-2000 | Fixed effects panel data analysis | Panel data (4) | No statistically significant results observed in any of the measures. e.g.: | OLS | No statistically significant results observed except in one case (see right). e.g.: | Over-estimate in one case: |
(a.) restaurants per 10,000 people, | (a.) -0.03 (-0.09, 0.02) | (a.) 0.03 (-0.03, 0.09) | ||||||||||
(b.) grocery stores per 10,000 people | (b.) -0.03 (-0.11, 0.05) | (b.) -0.0074 (-0.10, 0.08) | ||||||||||
(c.) physical activity facilities per 10,000 people | (c.) -0.12 (-0.2, 0.05) | (c.) -0.16* (-0.30,-0.02) | ||||||||||
Sandy, 2009, National Bureau of Economic Research [42] | U.S. young children (Indianapolis, Indiana) | Twenty different measures,3 including: | Yes | Individual addresses | BMI (z scores) | Clinical records, 1996-2006 | Fixed effects panel data analysis | Panel data (10) | In general, very few statistically significant results3 | Cross-sectional OLS | In general, very few statistically significant results. | Over-estimates in two cases3: |
However, some selected exceptions (within 0.25 miles and including children of all ages, unless otherwise stated): | ||||||||||||
(a.) restaurants | (a.) -0.08* [-0.13 at 0.1 miles] | (a.) 0.02 [0.08* at 0.1 mile] | ||||||||||
(b.) supermarkets | (b.) 0.05 (0.1 miles) | (b.) -0.19* (0.1 miles) | ||||||||||
Under-estimates in three cases3: | ||||||||||||
(c.)fitness, | (c.) -2.26* | (c.) 0.25 | ||||||||||
(d.) kickball, and | (d.) -0.08* | (d.) 0.04 | ||||||||||
(e.) volleyball facilities | (e.) -0.90* (0.1 miles; children <8 years only) | (e.) 0.03 (0.1 miles; children <8 years only) | ||||||||||
All within 0.25 miles and including children of all ages, unless otherwise stated | ||||||||||||