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 Table of Contents  
Year : 2020  |  Volume : 64  |  Issue : 3  |  Page : 300-303  

Spatial analysis of hypothyroidism and ground water pH in an Urban Area of Kerala using the geographic information system

1 PhD Student, Achutha Menon Centre for Health Science Studies, Sree Chitra Tirunal Institute for Medical Science and Technology, Thiruvananthapuram, Kerala, India
2 Principal, Government Medical College, Thiruvananthapuram, Kerala, India
3 Superintendent, Department of Health Services, Government of Kerala, Thiruvananthapuram, Kerala, India
4 Director, International and Inter University Centre for Natural Resources Management, University of Kerala, Thiruvananthapuram, Kerala, India
5 Research Fellow, International and Inter University Centre for Natural Resources Management, University of Kerala, Thiruvananthapuram, Kerala, India
6 Associate Professor, Department of Community Medicine, Government Medical College, Thiruvananthapuram, Kerala, India

Date of Submission01-Jul-2019
Date of Decision01-Apr-2020
Date of Acceptance02-Jun-2020
Date of Web Publication22-Sep-2020

Correspondence Address:
Mathew Joseph Valamparampil
Achutha Menon Centre for Health Science Studies, Sree Chitra Tirunal Institute for Medical Science and Technology, Thiruvananthapuram - 695 011, Kerala
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/ijph.IJPH_301_19

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Hypothyroidism is a disease assuming increasing relevance. The causative role of acidic nature of drinking water has not yet been investigated in Kerala. We attempted to determine the spatial association between the occurrence of self-reported hypothyroidism and pH of ground water using the geographic information system. The cross-sectional study was conducted among 1649 individuals residing in the subcenter area in urban Trivandrum. Self-reported hypothyroidism was obtained by the interview. Differential Global Positioning System was used to record the location of each house and its drinking water source. PH of 50 open-well water samples was estimated. The prevalence of self-reported hypothyroidism was 4.24%. Maps depicting pH distribution and occurrence of hypothyroidism were prepared. Most of the areas had acidic ground water. Geo-statistical analysis revealed the occurrence of statistically significant clustering of hypothyroid individuals in areas having acidic ground water. The study brings out possible linkage between hypothyroidism and acidic water intake necessitating detailed epidemiological investigations for drawing more robust associations.

Keywords: Geographic Information Systems, groundwater, hypothyroidism, India, spatial analysis

How to cite this article:
Valamparampil MJ, Varghese S, Mohan A, Reghunath R, Achu A L, Anish T S. Spatial analysis of hypothyroidism and ground water pH in an Urban Area of Kerala using the geographic information system. Indian J Public Health 2020;64:300-3

How to cite this URL:
Valamparampil MJ, Varghese S, Mohan A, Reghunath R, Achu A L, Anish T S. Spatial analysis of hypothyroidism and ground water pH in an Urban Area of Kerala using the geographic information system. Indian J Public Health [serial online] 2020 [cited 2021 Nov 27];64:300-3. Available from:

Disease is a function of the epidemiological triad of agent, host, and environment. The factors of external environment are spatially controlled, and hence, the agents and hosts also have specific location characteristics. The relationships between environment and health are thus intrinsically geographical, that is, the interaction between the geographies of the agent and of the host. Geographic Information System (GIS) is gaining the attention of the policy-makers in health, due to the ease with which the components of the epidemiological triad can be assessed and analyzed in various combinations. The disease causing agent and the human host interacting in favorable environments can be conveniently depicted for easy understanding and prompt management with the help of Medical GIS.[1]

Concerns regarding the occurrence of disease clusters in different parts of the world are very common. Clusters of health events may be identified by an ongoing surveillance system or by concerned people or agencies. Disease-clustering investigations are useful in actively identifying outbreaks or might be used to generate ideas and hypotheses regarding disease etiology. The role of geographical influences in noncommunicable disease causation is increasingly gaining attention among health-care professionals and policy-makers.

Hypothyroidism is a disease assuming increasing relevance. Iodine deficiency remains as the most important cause of hypothyroidism worldwide. In areas of iodine sufficiency, autoimmune diseases and iatrogenic factors are the most important causes. The secondary causes of hypothyroidism include hypothalamic diseases, hypopituitarism or rarely, isolated thyroid stimulating hormone deficiency.[2] Even though the disease predominantly affects women, increasing number of men are also getting affected.[3] Besides, congenital hypothyroidism occurs in about 1 in 4000 newborns, resulting in high morbidity due to varying degrees of permanent neurologic damage.[2]

Although the above-said causes are considered as the most significant, an important role has been advocated for the acidic nature of drinking water, which has not yet been thoroughly investigated in Kerala.[4] Acidic nature of water favors the dissolution of nitrates, perchlorates, etc., which have been proven to be important in causing hypothyroidism in humans.[4],[5] Abnormal ground water pH has been found to be widespread in Kerala in the past and present and the causes have been thought to be excessive amounts of nitrates and perchlorates.[6],[7] Hence, the role of drinking water quality in the occurrence of hypothyroidism requires a thorough investigation. Although ground water quality and water supply practices have been studied in detail using remote sensing and GIS, investigations relating to water quality and health are very few.[8] The objective of the present study was to examine the spatial association between the occurrence of self-reported hypothyroidism in individuals and pH of ground water in an urban area of Trivandrum using GIS. The secondary objective is to find the prevalence and determinants of hypothyroidism.

The present study was conducted as a community-based cross-sectional investigation in a sub-center area of an Urban Health Centre at Thiruvananthapuram, Kerala, during February to May of 2016. A “sub-center” is the smallest defined healthcare unit in the community, usually catering to a population of roughly 4000–5000 people. The studied sub-center was selected randomly from a total of 11 sub-centers under the field practice area of a Government Medical College in Kerala, India. Institutional Ethical Clearance for the study was obtained from the Human Ethics Committee of Government Medical College, Trivandrum, India (IEC No: 01/28/2016/MCT). Written informed consent was obtained from the individual participants.

The study area comprises 540 individual houses and 274 apartments in 4 multi-storied buildings. All the individual houses were recruited in the study (census method), and all the individuals in the houses who have resided in the area for a minimum duration of 2 years were considered as study participants. Details regarding individuals were obtained, from an adult member of the household present at the time of data collection, using a semi-structured questionnaire. Dwellings found closed/uninhabited were visited on 3 separate days, at different times of the day and still found to be locked were excluded. Apartments in multistoried buildings were also excluded from the present analysis as only one location could be attributed to these houses which are located vertically. Thus, a total of 452 houses were finally included in the study.

All individuals residing in the 452 occupied houses were recruited into the study. Each of the dwellings was visited by a team of two investigators – one doctor and one GIS expert. Training was provided before data collection for ensuring the quality of data. A semistructured questionnaire was used for assessing the details regarding age, gender, socioeconomic status, and existing self-reported illnesses including hypothyroidism of each family member. An individual is stated to be affected with a hypothyroidism if he/she has a history of taking medications presently which was verified by the doctor by checking the treatment documents, drug prescriptions, or tablet strips. The questionnaires were verified at the end of each day for ensuring completion and quality of data.

Remote-sensing data products were used to prepare various geo-environment-related thematic maps. The entire data were later collated in the ArcGIS platform for the analysis using appropriate statistical and spatial software. Data regarding hypothyroidism were entered into Microsoft Excel spread sheet. The two data sets were compiled on Arc GIS software for the creation of the spot maps. Hotspot maps of hypothyroidism and groundwater pH were prepared. Descriptive and analytical statistics were performed using the SPSS software version 16.0.

pH of water samples from 50 open wells was estimated by a subsequent visit to the households by the investigators. These wells served as the sources of drinking water for the respective households. The wells from which the water was to be sampled were determined by considering the soil texture, the slope of the terrain, and the land use pattern. The pH of these samples was interpolated to create a gradient map of ground water pH.

The mean (standard deviation) age of the 1649 study population was 37.72 (21.53) years. Of the 810 males, 12 (1.5%) were reported to have hypothyroidism, whereas 58 (6.9%) out of the 839 females had the same. Overall self-reported prevalence of hypothyroidism in the population was 4.24% (3.26–5.22) [Table 1].
Table 1: Self-reported hypothyroidism according to age and gender in the study area (n=1649)

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The spatial analysis of the houses where the disease was reported which shows weak clusters [Figure 1]. Interpolated gradient maps showing ground water pH of the entire study area revealed that the ground water in the area was acidic with a major portion of the area falling in the pH range of 5–5.5. This is an alarming situation since the WHO standards specify a pH of 6.5–8.3 for drinking water. A spot map of self-reported hypothyroidism was over layered on the ground water pH map [Figure 2], and it shows there were no major clusters, but most of the cases were located in low pH (<5.5) areas having acidic ground water. Geostatistical analysis also revealed the occurrence of statistically significant clustering of hypothyroidism (99% confidence) mostly in areas having highly acidic ground water. The analysis has accounted for the varying population density across the study area by using the spatial autocorrelation methods. This has ensured that no false hotspots are created just due to the increased number of individuals with hypothyroidism residing at a particular location. However, the presence of houses in the low pH zone, without any reported disease, probably points that they depend on a different source rather than ground water for drinking purpose.
Figure 1: Distribution map of individuals with hypothyroidism.

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Figure 2: Hotspot map of hypothyroidism and groundwater pH.

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The biologic potency of the thyroid hormone is largely dependent on the metabolic transformations occurring at the peripheral tissue. This is a major difference from other hormones released in the human body. The individuals with hypothyroidism are almost seen to be uniformly distributed in the study area with no major clustering. Despite this, the occurrence of significant hotspots in areas with acidic water is a major finding from the study. Ground water pH has been found to be abnormal in Kerala in the past too.[6] The association of high nitrate levels in ground water with subclinical hypothyroidism has been shown in previously.[4] The high levels of perchlorate in ground water in Kerala as proven recently is also a grave concern due its role in influencing ground water pH.[7] Hence, the association between hypothyroidism and low ground water pH as evidenced from this study is of high priority for places such as Kerala in low- and middle-income countries (LMICs). This is because large majority of population draws drinking water from various ground water sources directly due to the lack of availability of centralized treated drinking water supply. However, in this study, the absence of significant disease hotspots in all areas with lower pH and the presence in some areas with better pH demands detailed epidemiological investigations to account for all the exposure factors.

The prevalence of self-reported hypothyroidism was found to be much higher among women than men as is always seen for the disease. Even though the numbers were lower than what was detected from some earlier Indian studies[3],[9] by means of clinical and laboratory assessment, the proportion of affected individuals in the community is not low either. This prevalence is higher than what is seen in developed countries as evidenced from the HUNT study.[10] The lower prevalence could be due to the higher proportion of undetected subclinical cases which is usually seen with hypothyroidism.[3] The use of laboratory techniques for determining the prevalence would have yielded higher prevalence rates. This was not done as it was not the primary objective of this study. The prevalence of 6.9% among women is an ominous sign due to the high morbidity of the disease and also due to the risk for increased occurrence conditions such as mental retardation and congenital hypothyroidism in infants.

The limitations of the study include the inability to do spatial regression analysis using all available exposure variables of hypothyroidism. Temporal changes in groundwater pH have not been accounted for. Furthermore, the association between ground water pH and hypothyroidism lacks directionality due to the inability to ascertain the exact pH cutoff which is a risk factor for hypothyroidism.

The study highlights lower ground water pH as upcoming threats for hypothyroidism. This points to the need for the periodic use of accurate measurement tools for the assessment of drinking water quality along with the conventional approaches aimed at tackling hypothyroidism in rapidly expanding urban and rural areas in India and other LMICs.

Financial support and sponsorship

Funding is provided by the State Board of Medical Research of the State of Kerala, India. Award number A2-SBMR(2015-2016)/17351/2015/MCT.

Conflicts of interest

There are no conflicts of interest.

   References Top

Musa GJ, Chiang PH, Sylk T, Bavley R, Keating W, Lakew B, et al. Use of GIS mapping as a public health tool-from cholera to cancer. Health Serv Insights 2013;6:111-6.  Back to cited text no. 1
Longo F, Kasper H, Jameson L. Harrisons Principles of Internal Medicine. 18th ed. United States of America: The McGraw Hill Companies Inc.; 2011. p. 4881-84.  Back to cited text no. 2
Marwaha RK, Tandon N, Ganie MA, Kanwar R, Sastry A, Garg MK, et al. Status of thyroid function in Indian adults: Two decades after universal salt iodization. J Assoc Physicians India 2012;60:32-6.  Back to cited text no. 3
Aschebrook-Kilfoy B, Heltshe SL, Nuckols JR, Sabra MM, Shuldiner AR, Mitchell BD, et al. Modeled nitrate levels in well water supplies and prevalence of abnormal thyroid conditions among the Old Order Amish in Pennsylvania. Environ Health 2012;11:6.  Back to cited text no. 4
Buffler PA, Kelsh MA, Lau EC, Edinboro CH, Barnard JC, Rutherford GW, et al. Thyroid function and perchlorate in drinking water: An evaluation among California newborns, 1998. Environ Health Perspect 2006;114:798-804.  Back to cited text no. 5
Rejith PG, Jeeva SP, Vijith H, Sowmya M, Hatha AA. Determination of groundwater quality index of a highland village of Kerala (India) using Geographical Information System. J Environ Health 2009;71:51-8.  Back to cited text no. 6
Nadaraja AV, Puthiyaveettil PG, Bhaskaran K. Surveillance of perchlorate in ground water, surface water and bottled water in Kerala, India. J Environ Health Sci Eng 2015;13:56.  Back to cited text no. 7
Asadi SS, Vuppala P, Reddy MA. Remote sensing and GIS techniques for evaluation of groundwater quality in municipal corporation of Hyderabad (Zone-V), India. Int J Environ Res Public Health 2007;4:45-52.  Back to cited text no. 8
Usha Menon V, Sundaram KR, Unnikrishnan AG, Jayakumar RV, Nair V, Kumar H. High prevalence of undetected thyroid disorders in an iodine sufficient adult south Indian population. J Indian Med Assoc 2009;107:72-7.  Back to cited text no. 9
Asvold BO, Vatten LJ, Bjøro T. Changes in the prevalence of hypothyroidism: The HUNT Study in Norway. Eur J Endocrinol 2013;169:613-20.  Back to cited text no. 10


  [Figure 1], [Figure 2]

  [Table 1]


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