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Decrease in Average Height of Adults in India Alarming: Study

Non-genetic factors like food intake, standard of living and health care play a big role in determining height.
Decrease in Average Height of Adults in India Alarming: Study

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The average height of adults in India is declining as against an increase in average heights worldwide. The situation is alarming, pointed out a recent study titled ‘Trends of adult height in India from 1998 to 2015: Evidence from the National Family and Health Survey’.

In the context of an overall increase in average heights worldwide, the decline in average height of adults in India is alarming and demands an urgent enquiry. The argument for different standards of height for the Indian population as different genetic groups needs further scrutiny,” the authors of the study said. However, the trends from India clearly underline the need to examine the non-genetic factors and also to understand the interplay of genetic, nutritional and other social and environmental determinants on height, they added.

To trace the trends of height among adults in India, the authors conducted quantitative secondary data analysis to explore the variation in height. The data on height on a large scale is collected under the erstwhile National Nutritional Monitoring Bureau (NNMB) and the National Family Health Survey (NFHS).

In the 15-25 age group, the mean height of Indian women showed significant improvement between NFHS-II and NFHS-III. However, between NFHS-III and NFHS-IV, their average height declined by 0.12 cm. Between NFHS-III and IV, tribal women in the same age group showed a significant decline in their average height by 0.42 cm. The average height of women in the poorest wealth index category was observed to have suffered a significant decline.

The average height of Indian men in this age group has significantly declined by 1.10 cm between NFHS-III and IV. The decline in average height was observed across religious group, caste or tribe, residence and wealth index.

The state-wise trends of average height of men in 15-25 age group find only men from Nagaland showing significant improvement in their average height. Himachal Pradesh, Manipur, Meghalaya, and Mizoram also showed improvement in the average height of men while rest of the states exhibited decline.

Height is widely accepted and recognised as one of the key measures of physical well-being and biological standard of living at the population level. In addition to genetic potential, other factors such as socio-economic condition, disease history, access to quality health services, and nutritional security have a significant bearing on human stature, according to the study.

The role of nutrition over stature, however, has had a long and contested history among nutritionists, policymakers and health professionals. In India, the debate was recently fuelled by Dr [Arvind] Panagariya’s argument on stunting and subsequent critiques of it by various scholars. Evidently, much of this scholarship on stunting and height has focused on children,” the authors said. But “little attention has been paid to adult height, a more or less constant phenomenon having a higher potential for exploration of determinants”, they added.

The authors pointed out that genetic, environmental and social factors influence height. Although it is claimed that genetic factors determine 60%–80% of the final height, environmental and social factors contribute significantly to the realisation of that potential. The genetic potential in this case refers to an optimum level of height achievable in ideal conditions.

An individual’s realisation of the given genetic potential is a reflection of food intake as well as availability, accessibility and effectiveness of health care services during the growing period. It is well established that the attained height of an individual is an embodiment of nutritional status and other determinants traced from womb to late adolescence,” the study stated.

Several studies in economics, health and nutrition demonstrate the relationship between gross domestic product, per capita expenditure on food, net nutritional intake, disease occurrence and stature. The authors said: “Adequate nutrition is closely linked with an individual’s achievement of his/her genetic potential of height growth. The impact of nutrition on height gain can start as early as foetal life. Malnutrition during infancy, especially stunting around puberty, significantly affects the final height gain in adulthood.”

On the other hand, “overall change in factors such as nutrition, sanitation, hygiene, transport and income have been found to positively impact height and weight gain among Indian schoolchildren. The international study of childhood poverty found the Mid Day Meal programme to have improved both stunting and underweight”.

According to the study, deficits in final height or the failure of realisation of genetic potential of a population ultimately reflect prior nutritional stress, which is conditioned by social and environmental factors over time. Socioeconomic factors, like household characteristics (number of siblings, occupation, class and locality, etc.), have a bearing on human stature. Caste is another social factor that shapes different socioeconomic determinants and consequent inequality across different aspects of life in India.

Data from NFHS-IV showed strong and significant correlation between average adult height and social category. The average height of people belonging to the Scheduled Tribe and Scheduled Caste category were found to be shorter than Other Backward Classes and others. Moreover, across all these categories, the richest in the wealth index had the highest mean height while the poorest had the lowest, clearly signalling the role of class, the study showed.

Analysis of NFHS III data shows higher socioeconomic status to be associated with greater height and greater secular increase in height. So far as gender is concerned, over time, the average heights of both Indian males and females have improved but the improvement was higher in males compared to females.”

According to the authors, despite considerable evidence to the contrary, the role of genetic factors has often been used to downplay the role of food intake, standard of living and health care, especially in countries like India. The role of socioeconomic and environmental factors is left out of the equation.

The authors raised questions like “what is the genetic potential for height in Indian population?” Is it different for other countries or population groups? Are we achieving that genetic potential? What factors shape realisation of the given genetic potential?

The authors concluded that “the trends from India clearly underline the need for examining the non-genetic factors to understand and find solutions to these disturbing trends”.

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