Mapping of India’s Contribution on “Down Syndrome” During 40 Years From 1973-2012

Down syndrome, a genetic disease, is commonly diagnosed congenital malformation/mental retardation syndrome occurring in people of all races and economic levels. The present study is aimed to examine the contribution of Indian scientists on Down syndrome during the 40 years span from 1973-2012. The study analyses the Indian share in the research output, contribution and citation impact of top Indian institutions, most prolific Indian authors, top journals for publication, top collaborating countries, number of citations received and the highly cited papers in the Indian research on Down syndrome.


INTRODUCTION
Down syndrome (DS) or Down's syndrome, also known as trisomy 21, is a genetic disorder caused by the presence of all or part of a third copy of chromosome 21. It is the most commonly diagnosed congenital malformation/mental retardation syndrome (Jones, 2006). The additional genetic material alters the course of development and causes the characteristics associated with Down syndrome. A few of the common physical traits of Down syndrome are low muscle tone, small stature, an upward slant to the eyes, and a single deep crease across the center of the palm -although each person with Down syndrome is a unique individual and may possess these characteristics to different degrees, or not at all (NDDS, n.d.). Some of the complications due to Down syndrome, as given in Merck Manual Home Health Handbook for Patients and Caregivers, are shown in Table 1. Abnormally formed heart chambers

Muscles and bones
Unstable connections between the first 2 bones in the neck Loose joints *Not all complications are present in each person Down syndrome is estimated to affect 1 in 750 live births (Jones, 2006); however, several reports have indicated variability in the estimates of Down syndrome among different ethnic groups. According to WHO, the estimated incidence of Down syndrome is between 1 in 1,000 to 1 in 1,100 live births worldwide. In India, the reported incidence of Down syndrome is around 1 in 1250 live births (Verma, 2006). According to an article published in the leading newspaper Deccan Herald, every year between 23,000 and 29,000 children are born in India with Down syndrome.
Down syndrome occurs in people of all races and economic levels, though older women have an increased chance of having a child with Down syndrome. A 35 year old woman has about a one in 350 chance of conceiving a child with Down syndrome, and this chance increases gradually to 1 in 100 by age 40. At age 45 the incidence becomes approximately 1 in 30. The age of the mother does not seem to be linked to the risk of translocation. To study the effect of advanced maternal age on Down syndrome many hypotheses have been formulated. Initially Penrose identified that advanced maternal age as risk for Down syndrome birth (Penrose 1933(Penrose , 1934) and postulated that the maternal age dependent increase in birth rate of Down syndrome is in some way associated with the non-disjunction mechanism. The biological ageing hypothesis was originally proposed by Brook et al (1984), the central idea of which was that the increasing rate of meiotic errors and subsequent aneuploid birth is related to 'biological aging' of ovary not to the chronological age of women. Ghosh et al. (2010), proposed 'genetic aging' hypothesis which states that some of the mothers who have Down Syndrome baby are genetically older than the mothers of same chronological age who have euploid baby.

OBJECTIVES OF THE STUDY
The main objective of the present study is to analyse India's research productivity on Down syndrome during 1973-2012. The specific objectives of the study include: o To find out Indian share in the research output on Down syndrome. o To study the contribution and citation impact of top Indian institutions conducting research on Down syndrome. o To find out the most prolific Indian authors conducting research on Down syndrome. o To study the various source journals and the top journals preferred for publication.

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o To find out the top countries collaborating with India for research on Down syndrome. o To analyse the citation profile of the papers and to find out highly cited papers.

MATERIALS AND METHODS
The present study is based on the publications data on Down syndrome by Indian research community retrieved from Scopus database during November 2013. Scopus is the world's largest abstract and citation database of peer-reviewed literature. It covers nearly 20,500 titles from over 5,000 international publishers, of which 19,500 are peerreviewed journals in the scientific, technical, medical, and social sciences (including arts and humanities). For retrieving relevant information for the present study the phrases "Down's syndrome", "Down syndrome", "Downs syndrome", "Trisomy 21" were used in the TITLE-ABS-KEY search option and "India" in the AFFILCOUNTRY option. The data was selected for the 40 years time period from 1973-2012. The results were refined to obtain relevant data regarding authors, institutions, source journals, etc. A different search strategy was used for finding the international collaborations and the results obtained were analyzed manually to obtain relevant results. The citations received by the article were taken as the citations which any article received since its publication. However, Scopus doesnot provide complete citations before 1996. This may be considered the limitation of the present study.

Global Publication Share
The global publication share of top 15 most productive countries on Down syndrome research varies from 1.20% to 28.34% during 1973-2012. United States tops the list with 8144 publications with a share of 28.34% of total publications. Second rank is held by United Kingdom with 3680 publications and a share of 12.81%. Italy ranks third (4.98%) and France fourth (4.57%). These are followed by Japan (3.83%, 5 th rank), Germany (3.73%, 6 th rank), Canada (3.53%, 7 th rank), Spain (3.07%, 8 th rank), Netherlands (2.66%, 9 th rank) and Australia (2.47%, 10 th rank). Israel, India, Switzerland, Brazil and Sweden ranks 11 th to 15 th respectively (with publication share from 1.20% to 1.73%). Thus, India holds the 12 th rank with 405 (1.41%) publications.
The overall publication output of maximum countries shows an increasing trend from 1973-2012 except for some countries which showed a decline at some point of time. United Kingdom had a decline in its share from 16.  Table 2. It was lowest for India (4.14). The h-index for Down syndrome publications was highest for United States (157), followed by United Kingdom (106) and Germany (68). It was low for Brazil (25) and India (19).

Down Syndrome Research Output in Context of Different Subjects
As reflected in Scopus database classification (based on journal subject), India's publication output on Down syndrome research during 1973-2012 has been published in context of 6 subjects with highest publications output coming from medicine (342 papers, 84.44% share), followed by Biochemistry, Genetics and Molecular Biology (109 papers, 26.91% share), Neuroscience (15 papers, 3.7% share), Pharmacology, Toxicology and Pharmaceutics (14 papers, 3.46% share), Dentistry (10 papers, 2.47% share) and Health Professions (5 papers, 1.23% share) (see Table 4).
The citation impact of each subject category was also analyzed and it was found that Neuroscience have highest citation impact (7.80 citations per paper), followed by Pharmacology, Toxicology and Pharmaceutics (7.50 citations per paper), Biochemistry, Genetics and Molecular Biology (4.99 citations per paper), Dentistry (4.7 citations per paper), Health Professions (4.6 citations per paper) and Medicine (3.86 citations per paper). The subject category Medicine has the highest number of papers as well as citations but the average citation per paper is low.

Top Contributing Institutions of India on Down Syndrome
The top 16 most productive Indian institutions in Down syndrome research publishing 5 or more papers are given in Table 5

Most Productive Indian Authors on Down Syndrome
There are 14 authors who have published 6 or more papers on Down syndrome during 1973-2012. The publication profile of these 14 authors along with their research output, citations and h-index value are given in Table 6

Media of Research Communication
Out of the total 405 Indian publications on Down syndrome 398 appeared in journals, 6 in conference proceedings and 1 in book. The frequency distribution of publications in various source journals/ conferences is shown in Table 7. It was found that there are 118 journals in which only one paper is published and 28 journals in which two papers each were published. The Indian authors published 42 papers in just one journal titled Indian Journal of Pediatrics.

Top Source Journals for Publishing Indian Research on Down Syndrome
The 20 most productive journals publishing Indian research on Down syndrome are shown in Table 8 table 9). The maximum international collaborative papers are with United States (13 papers) and United Kingdom (10 papers). The top international institutions collaborating with India includes University of Pittsburgh Graduate School of Public Health (4 papers), The University of North Carolina at Chapel Hill (2 papers) and Dongguk University, Gyeongju (2 papers).

Citation Profile and Highly Cited Papers
The citation profile of Indian publications on Down syndrome during 1973-2012 is shown in Table 10. Out of the total 405 papers 249 papers (61.48%) have received atleast one citation during 1973-2012 with a cumulative total of 1676 citations. 156 papers (38.52%) did not receive any citation at all. Out of the 249 papers receiving citations, 1 paper received more than 100 citations, 3 papers received citations between 51 to 100, 3 papers received citations between 41 to 50, 4 papers received 31 to 40 citations, 7 papers received 21 to 30 citations, 19 papers received 11 to 20 citations and 212 papers received upto 10 citations.
The top 18 highly cited papers which have been cited more than 20 times are shown in Table 11. Out of these, only 2 are single authored papers and the rest have two or more

SUMMARY AND CONCLUSIONS
The analysis of literature on Down syndrome (during 1973-2012) obtained through Scopus database reveals that the United States account for maximum literature (28.34%) on Down syndrome followed by United Kingdom (with a share of 12.81%). India, with a global share of 1.41% (405 publications), stands at 12 th place in publication output on Down syndrome indicating that the contributions by Indian authors in this area are low. The maximum Indian publications (71.11%) appeared during last 10 years from 2003-2012. The overall citation impact is also not very high with 4.14 citations per paper from 1973-2012.
All India Institute of Medical Sciences, New Delhi is the most productive institution with 46 publications during 1973-2012. The most prolific Indian author is I.C. Verma of Sir Ganga Ram Hospital, New Delhi who published 15 papers and received 167 citations (11.13 citations per paper). The Indian Journal of Pediatrics was most preferred by Indian authors for publishing their research. International collaboration was seen in 38 papers (9.38%) and the maximum collaboration (13 papers) was with United States. About 62% of the total Indian papers have been cited by others and there are 18 papers which have been cited more than 20 times.
The bibliometric analysis of Down syndrome indicates that India's publication output is very small as compared to other countries. The Indian scientists need to focus more on this

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ILNS Volume 34 area of research and also increase international collaborations for research. Efforts can also be increased towards obtaining more research funding and creating awareness about the disease.