Academic journal article Canadian Journal of Public Health

Region-Level Obesity Projections and an Examination of Its Correlates in Quebec

Academic journal article Canadian Journal of Public Health

Region-Level Obesity Projections and an Examination of Its Correlates in Quebec

Article excerpt

Obesity programs and objectives are typically established at the global, national or provincial/state levels.1-3 However substantial heterogeneity in population health, risk factors and environment is often observed regionally, potentially rendering inefficient any planning and target setting based on information at these high levels.4,5 While most regional health jurisdictions have their own surveillance programs, there remains a lack of studies that collectively assess and compare inter-regional obesity levels and temporal trends within larger administrative territories. This gap in information could mask important region-level disparities, which could in turn hinder the effectiveness of obesity programs at high levels or their implementation at the regional level.

In addition, obesity surveillance and risk factor burden typically rely on cross-sectional prevalence rather than time trends. Prevalence measures provide "snapshots" of burden, i.e., the average proportion of a given population that is obese at a given time. These have formed the basis for monitoring and target setting in public health. For instance, the World Health Organization's (WHO) obesity-related target is to "halt the rise" in prevalence, while its recent report outlines prevalence estimates in hundreds of countries to monitor trends.6 Understanding and forecasting trends is an essential component of public health planning,7 but cross-sectional prevalence measures cannot directly provide the information for these. Further, associations between obesity prevalence and associated characteristics are difficult to interpret because these factors can have a cumulative effect over time that drives the observed prevalence. For instance, longitudinal analyses have found stronger correlations between child poverty and overweight at later time points than earlier ones.8,9 The strength of prevalence-risk factor associations observed at given points are thus dependent on the time when they happened to be measured.

Rather than prevalence, incidence, i.e., the number of new cases per year, is often considered the most useful metric in epidemiologic studies, but data are scarce. The mean annual change (or time trend) in obesity prevalence can be closely related to yearly incidence because the condition is generally long-term.10 The slope metric also has less inertia than prevalence, making it more readily altered by interventions. Trend information can thus be used to understand past and future burden and provide information on the longitudinal associations of behaviours and characteristics with obesity, supporting public health planning. Such factors include income and education,11,12 smoking,13 immigrant status,14,15 stress,16-19 social capital,20,21 and rural vs. urban environment,22-24 which can drive region-level heterogeneity in obesity as well as predict future obesity burden. However, understanding region-level variation in these behaviours and characteristics in relation to obesity is also usually limited to associations with obesity prevalence, rather than correlated with its time trend. The results of such an assessment would be useful for impact assessment of public health interventions and programs, as well as for planning future objectives.

The objectives of the current study are thus to i) construct historical time series (1987-2012) and projections (2013-2023) of obesity prevalence for 16 health regions in Quebec, Canada to assess region-level obesity, time trends and heterogeneity, and ii) compare the yearly rate of change of obesity prevalence vs. cross-sectional prevalence for explaining observed heterogeneity and as a correlate with region-level obesity correlates.

METHODS

Data source and variables

Obesity

Time series in obesity prevalence were constructed for the adult population (age 18+) in 16 of 18 health regions in Quebec. Data were extracted from 13 cross-sectional survey cycles that spanned 25 years (1987-2012) and comprised three surveys: the Quebec Health Survey (1987)25 and the Quebec Health and Social Survey (1992-1993, 1998),26 which were conducted by the Quebec Statistics Institute, and the Canadian Community Health Survey or CCHS (2000-2001, 2002, 2003, 2005, 2007, 2008, 2009, 2010, 2011, 2012)27,28 which was conducted by Statistics Canada. …

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