Impact of Oral Rehydration and Selected Public Health Interventions on Reduction of Mortality from Childhood Diarrhoeal Diseases in Mexico

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Introduction

Experiences in several countries indicate that selected public health interventions reduce mortality from diarrhoeal diseases (1, 2). Historically, improvements in basic sanitation, nutritional status, and hygiene education have had the greatest impact in this respect (3, 4). More recently, use of oral rehydration therapy (ORT) and measles vaccination have been reported to reduce short-term childhood mortality from diarrhoeal diseases (2, 5).

In Mexico mortality from diarrhoeal diseases has decreased over the last few decades, mainly because of general improvements in living conditions, an increase in school attendance, and in particular an increase in literacy campaigns for women, as well as improvements in basic sanitation. In 1984, a nationwide programme was implemented to promote use of the ORT formulation recommended by WHO in order to accelerate this trend in mortality reduction, mainly among children under 5 years of age.(a) Prior to this, ORT had been used only in a few public hospitals, with no measurable impact on mortality (6, 7). Since the launch of the national oral rehydration therapy programme, there has been an increase in the consumption of oral rehydration salts (ORS) and the reduction in mortality rates has been more evident. Among the other public health interventions that have been introduced in Mexico in recent years are the following: a universal immunization programme (UIP), with particular emphasis on measles immunization (8), a programme to increase the quality and availability of potable water (clean water programme (CWP)) (9), and an increase in women's education standards, which may have also influenced the decrease in diarrhoeal disease mortality, as has been observed in other countries (1, 10-12). Since the role played by these interventions in this decline had not been analysed, we carried out the present study to assess their impact on the decrease of diarrhoeal disease mortality and to estimate the relative impact of the national ORT programme on this reduction.

Methods

Secondary data analyses were carried out to study mortality trends in Mexico, correlating them with the use of ORT and other selected public health interventions.

Three periods were covered in the analyses, as outlined below.

* Stage 1(1978-83). Over this period (selected for purposes of comparison), ORT had not been introduced as a public health measure in the country.

* Stage 11 (1984-89). The government launched a nationwide programme to decrease diarrhoeal disease mortality (national ORT programme).

* Stage III (1990-93). In addition to the national ORT programme, the following public health and sanitation programmes were launched: in 1990, UIP, with an emphasis on measles immunization; and in 1991 there was a strong reinforcement of basic sanitation (COOP) before the arrival of cholera in Mexico.

Statistics on mortality trends were obtained from official records, as described below.

Mortality

Deaths caused by diarrhoeal diseases included codes A00 to A09 of the Tenth International Classification of Diseases (ICD-10). Mortality rates among under-5-year-olds, as well as the corresponding rates for the period 1978-93, were obtained from Ministry of Health records, which are calculated from data provided by the National Institute of Statistics, Geography and Informatics. The proportion of deaths that were registered by physicians is quite high in Mexico: 86.2% in 1978, increasing to 94.8% in 1992. Although there is underregistration of deaths, estimated in some Mexican states to be as high as 40% (13), this concerns mainly newborns, and hence affects only infant mortality. On the other hand, underregistration has decreased over the past 20 years, thus making the reduction of childhood mortality reported in this historical analysis all the more relevant.

Service statistics

Sanitation and education. Data on basic sanitation were obtained from the General Censuses of Population and Housing for 1970, 1980, and 1990, as well as from the reports of the National Water Commission for 1991, 1992, and 1993. …