Urban-Rural Differences in the Prevalence of Coronary Heart Disease and Its Risk Factors in Delhi

Article excerpt

Introduction

Public health planning in most developing countries has focused mainly on problems related to communicable diseases, which have been responsible for high morbidity and mortality (1). The situation is different in developed countries, such as the USA, where coronary heart disease is the leading cause of death (2). However, with changing lifestyles in developing countries such as India? chronic and degenerative diseases, including coronary heart disease, are making an increasingly important contribution to mortality statistics, particularly in urban areas.

Over the last three decades, great progress has been made in identifying the risk factors for coronary heart disease. Some of the preventive measures, such as cessation of smoking? management of hypertension both by pharmacological and nonpharmacological means, control of diabetes, reduction in intake of dietary saturated fats, and early diagnosis and management of hypercholesterolaemia, have resulted in a significant decline in mortality from the condition in the industrialized world. Nevertheless, the disease continues to be the leading cause of death in many countries.

Coronary heart disease is considered to be an important public health problem not only in developed countries but increasingly in developing countries such as India. In 1959, the WHO Expert Committee on Cardiovascular Diseases and Hypertension (3) recommended that epidemiological surveys be conducted in as many countries as possible, in order to analyse the risk factors and to determine the prevalence of the disease in different countries. Over the past three decades a few such studies have been conducted in India, but the majority have been confined to hospital populations or used a sample size that was too small and/or nonrandomized, making it difficult to draw any valid conclusions.

Materials and methods

A community-based epidemiological study was conducted over the period 1984-87 on 13723 adults in the age group 25-64 years living in Delhi and 3375 living in rural areas about 50km away from the city, to determine the prevalence of coronary heart disease and its risk factors. The cluster sampling methodology, using a randomized house-to-house survey, and the criteria for diagnosis have been published elsewhere (4, 5). The study was supported by ECG examination and analysis of fasting blood samples for lipids in subjects with clinically detected coronary heart disease and asymptomatic adults free of clinically manifest disease in every second and fifth household, respectively.

In the present study, the prevalence of coronary heart disease and its risk factors were compared in the two populations. The following risk factors were studied: family history of coronary heart disease, obesity, smoking, physical inactivity, hypertension, diabetes mellitus, and hyperlipidaemia. In addition, dietary intake of the following was also assessed: total and saturated fat, cholesterol, sodium, and alcohol.

The U.S. National Cholesterol Education Program Expert Panel on detection, evaluation and treatment of high blood cholesterol has defined desirable, borderline, and high levels of blood lipids as below the 50th percentile, between the 50th and 75th percentile, and above the 75th percentile values, respectively (6). For the present study, the cut-off levels of serum lipids were based on 50th percentile values obtained from the study population (Table 1).

Table 1: Cut-off levels of serum lipids used in the study

                                    Cut-off (mg/dl) in:

Blood lipid (mg/dl)              Urban sample   Rural sample

Total cholesterol                190            170
Low density lipoprotein (LDL)    110             90
   cholesterol
High density lipoprotein (HDL)    53             52
   cholesterol
Triglycerides                    120            138

Hypertension was defined as a systolic blood pressure of [is greater than] 160 mm Hg and/or a diastolic blood pressure of [is greater than] 90 mm Hg or currently taking anti-hypertensive drugs. …