Chronic Diseases of Lifestyle Research Unit

An Overview of Chronic Diseases of Lifestyle

Definition of Chronic Diseases of Lifestyle
Chronic diseases of lifestyle (CDL) are a group of diseases that share similar risk factors because of exposure, over many decades, to unhealthy diets, smoking, lack of exercise, and possibly stress. The major risk factors are high blood pressure, tobacco addiction, high blood cholesterol, diabetes and obesity. These result in various long-term disease processes, culminating in high mortality rates attributable to stroke, heart attack, tobacco- and nutrition-induced cancers, chronic bronchitis, emphysema, renal failure, and many others.
Internationally, these diseases are also known as ‘non-communicable diseases’ (NCDs) or ‘degenerative diseases’.

Chronic Diseases of Lifestyle in South Africa (pdf format, 2.33mb)

Background
The disease profile of the world is changing rapidly, especially in low and middle income countries. In 2005, 60% of deaths in the world were attributable to CDL. The 35 million deaths from CDL in 2005 were double the number of deaths for all infectious diseases (HIV/AIDS, tuberculosis, malaria), maternal and perinatal conditions, and nutritional deficiencies combined. Approximately four out of five CDL deaths occurred in low and middle-income countries, with heart disease, stroke, cancer, chronic respiratory diseases and diabetes being the main ones. While the global CDL burden is enormous, common risk factors are largely modifiable and therefore action can be taken to reduce the relevant morbidity and mortality. 

The main causes of CDL are known, which include an unhealthy diet, tobacco use and physical inactivity as the major modifiable risk factors. These are expressed through intermediate risk factors, such as raised blood glucose, abnormal blood lipids, high blood pressure and overweight/obesity. The relationship between the major modifiable risk factors and the main CDL is similar in all regions of the world (Figure 1).1,2

According to the World Health Organization (WHO),1,2 underlying determinants of CDL can be thought of as the "causes of the causes". These factors are beyond the individual’s control, and are characteristics of the social and structural environment. The Global Strategy on Diet, Physical Activity and Health recognises the role of stakeholders in creating healthy environments that enable and encourage behaviour change. Current socio-economic, cultural, political, and environmental determinants that have a significant influence on CDL are urbanisation, globalisation, and population ageing.2


Figure1. Causes of chronic diseases of lifestyle 1,2

The most important fact is that these CDL can be prevented. “There is abundant evidence to support the argument that a large percentage of CDL are preventable by changing modifiable and intermediate risk factors. Poor diet and physical inactivity directly account for 4.8 million deaths each year. Furthermore, poor diet and physical inactivity significantly influence intermediate risk factors that attribute to over 14 million deaths a year. This provides an imperative to develop evidence-based policies and supportive programmes to target these risk factors”.2

History of the Chronic Diseases of Lifestyle Unit and our Research
Community health research on chronic diseases of lifestyle in the MRC was initiated in 1975 at the National Research Institute of Nutritional Diseases (NRIND). This initiative was prompted by the high ischaemic heart disease mortality rates in white communities and headed by Prof Jacques Rossouw. In line with international developments in cardiovascular disease (CVD) epidemiology a major community-based CVD risk factor intervention project, CORIS, was launched in the south-western Cape in 1979.

This CVD research programme underwent major downsizing and in 1988, when the Centre for Epidemiological Research in Southern Africa (CERSA) was created under leadership of Drs Stephen Fellingham and Derek Yach. Two NRIND staff members, Dr Krisela Steyn and Ms Jean Fourie, joined this vibrant young group of researchers, as the division of Cardiovascular Diseases.

During 1995 this Division separated from CERSA to become the Chronic Diseases of Lifestyle (CDL) Programme to reflect the broader complex of unhealthy lifestyles, emerging risk factors and, eventually, interrelated outcomes]. Dr Krisela Steyn headed this Programme as part of the Community Health Group of the MRC.

CDL expanded its activities, not particularly in terms of full-time staff, but by collaborating with many institutions nationally and internationally. The Programme took on the management of the MRC’s thrust on ‘Chronic Diseases, Cancer and Ageing’. In 2001 during the restructuring of the MRC, the CDL Programme became a Unit. Dr Krisela Steyn’s leadership as Director ended in 2006 when she retired and Dr Nelia Steyn took over as Interim Director, a position she held for three years. When she resigned in 2009, Ms Jean Fourie was appointed Interim Manager.