Exercise as it relates to Disease/Built for bigger waistlines? Association of the built environment with physical activity and obesity in older adults

The following page is a critique of the article titled "Association of the built environment with physical activity and obesity in older persons" published by Berke et al. in 2007.

What is the background to this research?
Obesity can be described as an abnormal accumulation of body fat that presents a risk to health. Obesity is linked to the development of chronic diseases such as type II diabetes and is a strong predictor of premature death. Participation in regular physical activity plays a critical role in healthy aging as it can prevent or slow the development of chronic diseases and aid in the maintenance of functional independence. Therefore, it is crucial to understand factors that encourage habitual physical activity for the older population, such as the impact of built environments. The built environment is defined as human formed, developed, or structured areas. Neighbourhood aesthetics, convenience to destinations and other environmental attributes are believed to influence the walkability of a neighbourhood. With the high prevalence of obesity and chronic health conditions associated with inactivity, understanding how the built environment can influence health-related behaviours has become an important area of research.

Where is the research from?
The research was undertaken in King County, Washington, United States. Study participants were drawn from the Adult Changes in Thought study, (based in King County) a prospective, longitudinally designed cohort of older patients aimed at detecting the onset of dementia. An earlier study unrelated to the Adult Changes in Thought study, the Walkable and Bikable Communities project, provided scores for neighbourhood walkability for the King County region. The authors of this study have strong track records on research in this field. In particular, Ethan Berke, Eric Larson and Anne Moudon have all been involved in extensive research concerning the built environment, activity levels and health outcomes, spanning many real world settings and measuring a plethora of variables. The paper was published in the American Journal of Public Health. As of 2017 this journal had an impact factor of 4.380, ranked 4th of 156 titles in the public, environmental and occupational health category.

What kind of research was this?
The study adopted a cross sectional design in which 936 adults aged 65-97 participated. As per the nature of cross sectional research, it was an observational study, analyzing data from a population at a specific time point. Cross sectional analyses are a good way to determine prevalence but do not differentiate between cause and effect like longitudinal or RCT studies can. It is also difficult to control external variables in observational studies such as this one.

What did the research involve?
During in-person visits with participants, information was collected on physical activity levels and obesity. Measured height and weight were used to calculate body mass index. A self-report on physical activity was collected at each visit. A written survey queried participants on the number of times per week they took part in various physical activities lasting greater than 15 minutes per bout. The Adult Changes in Thought study also provided a number of covariates including age, income, depression and disease burden.

When examined holistically, the methodology used in this research was not the best approach. Many limitations exist within this analysis. The cross sectional nature of the study makes it difficult to establish a causal link between obesity and walkability. Furthermore, the use of self-reporting as opposed to objectively measuring physical activity introduces the potential of social desirability bias into the measure. The social bias issue has been proven in a number of studies. Despite the study model accounting for many important factors related to obesity and physical activity (e.g. income, education) the fact is that it did not consider other variables that affect walkability such as perception of safety and seasonality.

What were the basic results?
Odds ratios (OR's with 95% confidence intervals) for association of neighbourhood walkability score (interquartile range) and body mass index for participants living at same address ≥ 2yrs:

Note: Data presented only for people living at same address for ≥ 2yrs as it was hypothesized that the effect of the built environment on a change in BMI takes >2 years to detect.

The researchers interpreted two major points from their research:

• There was no significant association between higher neighbourhood walkability and the proportion of participants in the overweight or obese range. This is demonstrated in the table with odds ratios and p-values not reaching statistical significance. This makes sense as the study is cross sectional and therefore it is difficult to establish a causal link between walkability and obesity.

• However, the built environment, as described by neighbourhood walkability score, is associated with increased walking for exercise in both men and women. The association was seen at several buffer sizes (100, 500, 1000m) representing potential distances travelled by older people. This finding was likely hypothesized and validates the neighbourhood walkability scores provided by the Walkable and Bikable Communities project. This point is emphasized a lot more than the previous finding, most likely because it describes a positive association and is potentially something the authors predicted before conducting the study.

What conclusions can we take from this research?
Despite its limitations, the study is able to provide some general recommendations on the built environment and its relationship with physical activity and obesity in older adults although there are many questions still to be answered. In future, it would be ideal to create stronger methodologies with larger sample sizes to be more representative of the whole population and provide stronger evidence. Despite this, the study adds to the growing body of literature about the relationship of walkable communities and activity levels, both past and present.

Practical advice
In real world settings, living spaces that encourage physical activity and help reduce unhealthy body weight should be encouraged and are beneficial. Particularly older people, a growing proportion of society, may seek communities that promote active living. The demand for this type of residential environment could influence urban planners and developers to create communities that encourage walking and improve the health of residents. In addition, redesigning neighbourhoods or fixing barriers to walking, such as damaged sidewalks, to improve pedestrian safety might increase walking and improve health outcomes.

Further information/resources
For further information on the issue of the built environment, physical activity and obesity, check out:

NSW government - Healthy Built Environments: https://www.health.nsw.gov.au/urbanhealth/pages/default.aspx

Australia's physical activity and Sedentary Behaviour Guidelines: http://www.health.gov.au/internet/main/publishing.nsf/content/health-pubhlth-strateg-phys-act-guidelines

Healthy ageing - staying involved: https://www.betterhealth.vic.gov.au/health/HealthyLiving/healthy-ageing-stay-involved

Worldwide Overweight/Obesity Prevalence: http://www.who.int/news-room/fact-sheets/detail/obesity-and-overweight