Type 2 Diabetes Mellitus is a Metabolic disorder linked closely to obesity and sedentary lifestyle. It has become one of the rapidly growing public health issues. Globally, over 537 million adults are estimated to be living with diabetes. It is estimated that the global burden might reach 643 million by 2030.
The paradigm shifts in the lifestyle and the transition from rural to urban areas, particularly in the low- and middle-income countries, seems to be a crucial environmental determinant of the rising prevalence. The accelerating pace of urbanization, characterised by rising population density, and industrialisation poses a substantial risk for Type 2 Diabetes Mellitus.
It is imperative to understand the biological and behavioral mechanisms through which urban establishments affect the metabolism of glucose in an individual. This article delves into the multifactorial basis that connects rapid urbanization to diabetes. It also explores the preventive intervention strategy to curb the onset and progression of this dreadful disease.
Is there a link between Urbanization and Diabetes?
Researchers have identified a strong association between urban lifestyle and diabetes prevalence across various demographics. According to WHO, individuals residing in an urban landscape have 2-4 times more risk for developing T2DM compared to their rural counterparts. For instance, a study by Mohan et a., identified a twice as high prevalence rate in urban Indian households. It has been observed that migrants are the most affected, as they rapidly acquire the metabolic risk factors. This may happen within a few years of their relocation.
These studies suggest deep-rooted causal pathways that do link urban ecosystems to T2DM through either environmental exposures or unique behavioural changes.
Path from Urbanisation to Diabetes.
Urbanisation and technological advances go hand in hand. Technological advances allow an individual to get tasks done without having to move around, limiting his/her physical activity. Urban ecosystems often lack pedestrian infrastructure like a simple walkable footpath, green spaces or safe recreational areas. The increased work hours and sedentary screen-based tasks put further time-bound restrictions. The switch from walking to using automobiles, even for short-distance commutes, may offer comfort and save time, but it eventually curbs all the slightest possibility of physical mobility. This decline in daily energy expenditure contributes to central adipose deposition, dysfunction of the mitochondria, and insulin resistance, a key hallmark of T2DM.
Changes in dietary habits
Urbanisation is marked by an increased consumption of calorie-dense ultra processed foods. These are rich in refined carbohydrates, saturated fats and high levels of sugars. Intake of such a diet can result in postprandial hyperglycemia and exhaustion of the pancreatic beta cells. Often, these foods are cheaper and are marketed aggressively by the fast-food industry. It results in increased consumption, particularly by the lower socio-economic strata.
Environmental Pollution
Studies have established fine particulate matter (PM2.5) as a novel diabetogenic factor. These pollutants promote systemic inflammation and result in oxidative stress. It results in adipose tissue dysfunction and also impairs insulin sensitivity. Heavy metals and endocrine-disrupting chemicals like phthalates and BPA interfere with pancreatic beta cell function and disrupt insulin signalling.
Disruption of Circadian Rhythm
Urban environments have documented increased light pollution. This, along with irregular sleep-wake cycles and night shift work, impairs melatonin and cortisol regulation. This hampers the homeostasis and results in impaired glucose tolerance. Sleep deprivation elevates ghrelin and induces insulin resistance.
Psychosocial stress
Urban living is accompanied by exposure to certain chronic stressors such as financial burden, job insecurity, and interpersonal conflicts, etc. Chronic stress activates the Hypothalamic Pituitary axis and raises cortisol levels. This enhances hepatic gluconeogenesis and promotes deposition of fat in the viscera, thereby worsening glycemic control.
Urban stress can also result in behavioural risks. Individuals might indulge in emotional eating, alcohol consumption to mitigate stress. This can compound the existing metabolic risk.
Policy Dimension
Urban areas serve as magnets for the rural population by offering job opportunities and the promise of financial stability. The rapid migration can result in overcrowding and unequal housing and healthcare opportunities. Low-income urban developments are disproportionately affected. City slums are synonymous with Food Deserts. They lack access to healthy, affordable, nutritious food, while cheaper, unhealthy fast-food outlets proliferate. Even the urban healthcare systems are overburdened and underfunded. This eventually results in undiagnosed or poorly managed diabetes cases until complications arise.
Transgenerational link
These urban-induced metabolic changes can have a lasting transgenerational impact. If a female is exposed to stress, endocrine disruptors, while she’s pregnant, can result in epigenetic modifications (e.g DNA methylation, acetylation of histones). This predisposes the infant to insulin resistance and obesity. Urban lifestyle has been associated with accelerated metabolic risk independent of genetic predisposition.
Prevention Strategies
The causal association between urban livelihood and diabetes provides a targeted road map for prevention.
Primary prevention can be done at the policy level. Policies can promote health by prioritising and integrating physical health during urban planning and design. Development of pedestrian friendly walking spaces, public parks and affordable public transport can be some positive measures towards this domain.
The government can reshape the urban food environment by nutritional intervention. Certain measures include imposing taxes on sugar-sweetened beverages and ultra-processed food, subsidising healthy staples like fruits, vegetables, and whole grains, regulating fast food advertisement. establishing a farmer’s market.
Policies aimed at reducing air pollution and limiting industrial waste are critical to decrease the prevalence of diabetes. Workplace policies ensure work life balance, regular breaks can help to mitigate circadian disruptions.
Governments and municipalities must recognize diabetes as a disease of urban planning. Mobile platforms can be developed for tracking glucose levels, lifestyle coaching and early screening especially in slum areas. Multisectoral collaboration can assist in reducing the burden of diabetes.
Conclusion:
The diabetes epidemic, driven by urbanization, is not inevitable. It is a modifiable outcome of policy decisions, environmental engineering and social behaviour. As the global population becomes increasingly urban, the fight against diabetes will be won or lost in our cities.
