A novel understanding of obesity and diabetes population dynamics in cities

Bagger M1, D. Napier2, B.B. Jensen3, A. Moses4, Lund N1

1: Health Advocacy, Novo Nordisk A/S, Novo Allé 1, 2880 Bagsværd, Denmark
2: Department of Anthropology, University College London, 14 Taviton Street, WC1E 6BT London, United Kingdom
3: Steno Diabetes Center Copenhagen, Niels Steensens Vej 2, 2820 Gentofte, Denmark
4: Research & Development, Novo Nordisk A/S, Vandtårnsvej 112, 2860 Søborg, Denmark

Background:
The increase in diabetes prevalence is one of today’s major health challenges with 415 million people living with the condition globally, making diabetes responsible for 12% of the global health care expenditure (1). Without concerted action, 642 million will be affected by 2040 (1). However, many of the cases can be prevented or at least delayed (1).

Type 2 diabetes (T2D) is a complex disease influenced by various factors and long delays between causes and effects. The global rise in prevalence primarily is driven by population growth and ageing, physical inactivity, rising overweight and obesity (2) as well as unhealthy diet (3). Worldwide, obesity has more than doubled since 1980 (4). In 2014, 39% of adults or more than 1.9 billion adults were overweight – of these more than 600 million were obese equivalent to 13% of all adults (4). Obesity has a range of severe comorbidities including T2D (5).

Two thirds of people with diabetes are living in cities and this is expected to increase to three fourths in 2040 (1). Thus, cities have a great potential to contribute to tackle the obesity and diabetes challenges and reduce their healthcare burden.

A global partnership programme - Cities Changing Diabetes – was established in 2014 to improve the understanding of some of the factors driving the rise of diabetes in urban settings. The programme is a partnership of University College London, Steno Diabetes Center, Novo Nordisk, as well as a broad range of local partners. Since 2014, eight large and very diverse cities across the world have been enrolled in the programme: Copenhagen, Houston, Johannesburg, Mexico City, Rome, Shanghai, Tianjin, and Vancouver.

Aim:
To increase the understanding of drivers behind the escalating occurrence of T2DM in urban settings, we aim to illustrate the degree that obesity drives the current and future prevalence of T2DM in an open cohort. This makes it possible to estimate the extent to which obesity must be reduced to decrease or stabilise the projected increase in the T2DM prevalence.

Methods:
A global dynamic model will be built and project the global prevalence of T2DM, display how much of this is driven by obesity, and simulate different population dynamics between obesity and T2DM. The model – like all models - will express a simplified version of reality omitting details and including assumptions. Obesity and diabetes will be seen as a sequence of comorbidities - obesity potentially leading to T2DM with a certain probability. Only the contribution from obesity will be considered in driving the growth of T2DM in this model. Furthermore, the global model will be applied to illustrate the obesity and diabetes dynamics in different cities by feeding the respective prevalence of obesity and T2D into the model.

Results:
The model will estimate how much of the projected prevalence of T2DM is driven by obesity and how theoretical reductions in the obesity prevalence will impact the future prevalence of T2DM. Additionally, it will demonstrate scenarios of how much obesity should be reduced to stabilise or even reduce the projected diabetes prevalence. Similarly, the model will estimate the human and societal cost of inaction. Preliminary results will be presented at the time of conference revealing the obesity and diabetes dynamics globally and at city level.

Discussion:
The model is designed to assist policy makers in building a stronger case for developing and implementing more effective public health strategies to target a reduction of obesity as a means to prevent diabetes. City planners may use this model to estimate the impact of their public health actions.

References:
1. International Diabetes Federation: IDF Diabetes Atlas, 7th edn. 2015.
2. World Health Organization: Global NCD target. Halt the rise in diabetes. September 2016.
3. Frank BH: Globalization of Diabetes. Diabetes Care 2011;34:1249-57.
4. World Health Organization: Obesity and overweight Fact sheet No 311. January 2015.
5. Guh DP, Zhang W, Bansback N, et al: The incidence of co-morbidities related to obesity and overweight: a systematic review and meta-analysis. BMC Public Health 2009;9:88.