NRIs more prone to lifestyle ills

February 29, 2008
By Syed Akbar
Hyderabad, Feb 28: Indians living in the USA are prone to more number of diseases linked to diet and environment than other people living there, says a research study.
Senior researchers Pragna I Patel, Niyati U Mehta and others, who conducted the study involving scores of Asian Indians living in the US, found that "Asian Indians display a high prevalence of diseases linked to changes in diet and environment that have arisen as their lifestyle has become more westernised".
The study associated Indians with a high prevalence rate of diseases like atherosclerosis (narrowing of blood vessels), hypertension, diabetes, prostate cancer, Hirschsprung disease (enlargement of colon) and age-related macular (cornea) degeneration. As Indians are becoming more westernised both in diet and lifestyle, the prevalence of diseases associated with these lifestyle changes is increasing.
The researchers used 1200 genome-wide polymorphism in more than 400 individuals from 15 Indian language groups and compared their data with those of other populations living in America. The non-Indian populations studied for comparison were from Africa, Asia (including Central, Southern, Eastern, and South-East Asian populations), Americas (native populations of South and Central America, and native
populations of North America), Europe (including non-native European American populations, and Russia), Oceania (Australia, New Zealand, and the Pacific islands).
They also found that Indians constitute a distinct population-genetic cluster, and despite the geographic and linguistic diversity of the groups they exhibit a relatively low level of genetic heterogeneity.
The analysis of the data revealed that allele frequency differences between the different Indian language groups were small, and interestingly the variant alleles were present only in a subset of the Indian language groups.
"Our results also support the inclusion of the Indian population in disease-related genetic studies, as it exhibits unique genotype as well as phenotype characteristics that may yield new insights into the underlying causes of common diseases that are not available in other populations," they said.
Metabolic disorders have been found to have a disproportionately high prevalence in the Indian population, a phenomenon which is likely associated with the increasing westernisation of Indian. Prevalence of coronary artery disease in individuals of Indian origin is currently much higher than in other ethnic groups and is even increasing.
It is estimated that 18 per cent of the Indian population suffer from hypertension, one of the major risk factors associated with CAD, and that the prevalence of hypertension is also increasing within this population.
They said Type-2 diabetes is now reaching epidemic proportions among Indians, most prominently in urban Indians where there has been a very steep increase in prevalence over the last decade from 8.3 per cent in 1992 to around 17 per cent now. Other diseases are also found at varying frequencies in Indian population including
Hirschsprung disease, age-related macular degeneration, prostate cancer, and type-1 diabetes.
The frequencies of variants associated prostate cancer were similar to those of African populations. However, none showed a high similarity to the populations of Eastern Asia. This could reflect a greater degree of non-Asian compared to Asian gene flow into India during the course of its history.
One possible explanation for the differences between the trends in the Indian groups and other world populations could be the differential migration of non-Indian individuals into different parts of India during the course of its history.
"There could also be selective pressures that are unique to, more important in, or different in action in, India than the other world populations, and that also share a strong correlation with latitude," they observed.
The Asian Indian population represents a large population within which many complex-trait disorders are found at a high frequency. In some cases, such as coronary artery disease, Indians exhibit unique phenotypic characteristics that distinguish them from the other populations, suggesting that unique causative factors underlie this and possibly other related diseases.