Prediction of 10-year cardiovascular disease risk among Nicobarese Tribes of Andaman and Nicobar Islands

INTRODUCTION

Globally, cardiovascular diseases (CVDs) are the number one cause of mortality, and higher burden is seen in low- and middle-income countries, leading to overburdening of the public health system.^1-3. WHO data on increased CVDs in India is estimated to be one of the greatest of any country in the world and is the largest cause of morbidity and mortality in the Country.⁴

World Health Organization (WHO) and the International Society of Hypertension (ISH) provided CVD risk prediction charts for use in 2014.^5,6 In 2019, WHO released WHO HEARTS CVD Risk Management Charts [WHO HEARTS package, 2020] for conducting the community-based risk prediction. Using a risk score is a cost-effective tool to stratify the entire population. It provides a 10-year risk of major cardiovascular diseases. Its valuable tool for taking appropriate actions by respective health authorities and helpful in counseling patients to modify their lifestyles and comply with medical advices.^6,7

In the Indian sub-continent, as measured through surveys of NFHS-4 (2015-16) and NFHS-5 (2019-20), data related to risk factors of CVDs has shown an increase in trends in recent years, same is the trend in Andaman and Nicobar Islands, which is still on the higher side and the data is worrisome when we compare it with National averages in India.^8,9 With the increase in risk factors and an increased burden of NCDs, the Country is facing a double burden of both Communicable and non-communicable diseases.¹⁰ Few studies have been undertaken in India on the estimation of common CVD risk factors using these WHO risk prediction charts. Most of the studies were conducted in mainland India, and the availability of such evidence from the Andaman and Nicobar Islands is limited.

Our earlier studies on the general population of South Andaman have revealed that 32.4% and 5.8% of the rural population in South Andaman Islands are at moderate and high CVD risk, respectively.¹⁹ However, there are no studies on the indigenous tribal population of these Islands. The Nicobarese tribes are an Austroasiatic-speaking people of the Nicobar Islands, a chain of islands in the Bay of Bengal, north of Sumatra. These tribes are indigenous tribes, and these Islands are difficult to reach, rural, and remote in nature.¹⁸ Very little information on NCD risk factors is known among these tribes, and there are no studies on CVD risk stratification in these tribes. Therefore, this study is undertaken in these Islands to gather evidence on the distribution of NCD risk factors and to predict 10-year CVD risk for the Nicobarese tribal population. This study aimed to study the distribution and determinants of NCD risk factors among Nicobarese Tribes, and to predict the 10-year CVD risk among Nicobarese Tribes using WHO HEARTS risk based CVD tools.

METHODS

A community-based cross-sectional study was conducted during July 2023 to June 2024, among Nicobarese tribes residing in the Nicobar Islands. Adults aged≥40 years of age who do not have any established coronary heart disease and strokes were included in the study.

Inclusion criteria

Individuals ≥40years of age, who do not have any established coronary heart disease and stroke.

Sampling technique

Multi-stage random sampling technique was used. Nicobar district is divided into 03 tehsils, out of which one tehsil was selected through random sampling. All revenue villages in the tehsil were listed, and in the second stage, ten villages were randomly selected for the study. At the community level, in the selected villages, the first line list of all eligible individuals was prepared, and then, 38 individuals from the selected villages were randomly selected irrespective of gender who fulfilled the eligibility criteria.

Sample size

The sample size was calculated using the formula to estimate the proportion of one sample situation. To detect the prevalence of 22.14 % of moderate to high CVD risk, as determined by a previous relevant study conducted in South India,¹² minimum sample size required was 265, with an allowable error of 5% and a confidence interval of 95%. An additional 25% of the sample was added to account for non-response rate and with a design effect of 1.2, the final sample calculated was 384.

Study tools

WHO HEARTS CVD risk assessment tools for the South Asian region were used to assess the CVD risk. The predictor variables for the risk prediction were - age, gender, smoking, systolic BP, and BMI.A semi-structured interview schedule adapted from the WHO STEPS instrument for non-communicable diseases to collect socio-demographic details and CVD risk-related details.³⁰

Ethical approval

Owing to ethical considerations, ethical approval was obtained from the Institutional Ethics Committee (Human) of the ICMR–Regional Medical Research Centre, Port Blair.

Operational definitions

Diagnosis of hypertension: Classification of hypertension [National High BP Education program, 2004].²¹

Diagnosis of type-2 diabetes mellitus: RBS: 200 mg/dL or above. ²¹

Smokers: All current smokers and those who used any tobacco product (cigarettes, beedis, chewing tobacco, or snuff) on a regular basis for at least the previous 01year before the assessment. ²²

Alcohol users: Alcohol use refers to the intake of any form of alcohol in the past 12 months.

Overweight: BMI >23kg/m². BMI calculated using Quetelet's Index formula [WHO Expert Consultation 2004].²³

Data collection and statistical analysis

Anthropometric measurements

Weight was calculated using an EQUAL digital weighing scale with 180 kg capacity and with an accuracy of 100 gm, and height was measured using a stadiometer.

Assessment of blood pressure and blood sugar

Blood pressure was measured using Omron HEM-7120 Automatic Blood Pressure Monitor with two different-sized cuffs-one medium and one large size. Accu-Chek active blood glucose meter kit was used to measure blood glucose.

Statistical analysis

The statistical analyses were conducted using STATA 16 (Stata Statistical Software: Release 16. College Station, TX: StataCorp LLC). For risk assessment, the study employed the WHO CVD risk (non-laboratory–based) charts. Continuous variables were summarized using the median (interquartile range, IQR), while categorical variables were expressed as frequency and percentages. Bivariate analyses included Pearson's Chi-squared test and Fisher's exact test to examine associations among categorical variables. Subgroup comparisons for continuous variables utilized the Kruskal-Wallis rank sum and Wilcoxon rank sum tests. Factors influencing CVD risk classification were evaluated via univariable and multivariable multinomial logistic regression to determine relative risk ratios. Additionally, prevalence ratios for smoking, tobacco usage, obesity, hypertension, and alcohol consumption were computed using simple and multiple generalized linear models with binomial and log link functions. The selection of factors for regression models considered statistical significance and relevant literature after addressing multicollinearity and confounding effects. All statistical tests were two-sided with a type I error rate of alpha = 0.05.

RESULTS

With a response rate of 95.05%, 365 individuals participated in the study (Figure 1). Among the enrolled cohort, 161 (44.1%) were male, with a median age of 54 years (interquartile range: 47 to 62 years). A substantial proportion, 125 (34.2%), were illiterate. The majority, 361 (98.9%), identified as Nicobarese, and 199 (54.5%) were classified as lower socio-economic status. A notable portion, 244 (66.8%), had a BMI ≥23.0 (indicating obesity), while 89 (24.4%) were smokers. Smokeless tobacco use was prevalent among 273 (74.8%), and 228 (62.5%) reported alcohol consumption. None of the female participants were screened for cervical cancer during their lifetime. The median weekly intake of fruits and vegetables was three servings (interquartile range: 2 to 4), with 54 (14.8%) consuming excessive salt. Only 125 (34.2%) engaged in regular physical activity.

Based on the non-laboratory component of the CVD risk assessment chart, 83 (22.7%) had a risk <5%, 132 (36.2%) a risk of 5-9%, 114 (31.2%) a risk of 10-19%, 34 (9.3%) a risk of 20-29%, and 2 (0.5%) a risk of 30% and above.

Statistical analysis revealed several significant associations, including that moderate to high CVD risk scores were significantly associated with illiteracy and lower educational status (P=0.04), salaried/self-employment (P=0.029), alcohol use (P=0.006), lower level of vegetable consumption (P=0.007).

¹n; Median (IQR) or n (Col.), ²n; Median (IQR) or n (Row.), ³Pearson's Chi-squared test, ⁴Kruskal-Wallis rank sum test, ⁵Fisher's exact test

Factors such as male gender (p<0.001), employment status (p=0.008), non-tobacco use (p<0.001), alcohol consumption (p=0.004), and lower salt intake (p=0.004) were significantly associated with smoking status (Table 3). Smokeless tobacco use showed no significant associations except with smoking status (Table 4).

Alcohol consumption showed a significant association with higher risk scores (p=0.006) (Table 2). Factors associated with alcoholism included male gender (p<0.001), employment status (p<0.001), lower socio-economic status (p=0.006), smoking (p=0.004), tobacco use (p=0.002), non-diabetes (p=0.009), and lower salt consumption (p=0.032) (Table 5).

Obesity was significantly associated with higher blood pressure readings, known hypertension (p<0.001), diagnosed hypertension (p=0.011), and diabetes (p=0.046) (Table 6).

¹n; Median (IQR) or n (Row.), ²Pearson's Chi-squared test, ³Wilcoxon rank sum test, ⁴Fisher's exact test

¹n; Median (IQR) or n (Row.), ²Pearson's Chi-squared test, ³Wilcoxon rank sum test, ⁴Fisher's exact test

¹n; Median (IQR) or n (Row.), ²Pearson's Chi-squared test, ³Wilcoxon rank sum test

¹n; Median (IQR) or n (Row.), ²Pearson's Chi-squared test, ³Wilcoxon rank sum test, ⁴Fisher's exact test

Being male (aPR: 5.60, 95% CI: 3.39 to 9.54, p<0.001) and ever being married (aPR: 2.16, 95% CI: 1.01 to 4.65, p=0.048) were associated with higher prevalence of alcoholism, whereas upper or middle socio-economic status was associated with lower prevalence (aPR: 0.42, 95% CI: 0.26 to 0.68, p<0.001). Being male was also associated with a higher prevalence ratio (aRR: 2.01, 95% CI: 1.01 to 4.10, p=0.049) for being a smoker (Figure 2).

Analysis of relative risk ratios (aRR) highlighted that illiteracy (aRR: 2.24, 95% CI: 1.34 to 3.78, p=0.002) and lower vegetable consumption (aRR: 1.71, 95% CI: 1.04 to 2.81, p=0.035) were associated with a higher CVD risk score of 10-19%. Employment and lower vegetable consumption were associated with a higher risk score of ≥20% (aRR: 2.59, 95% CI: 1.14 to 6.01, p=0.024) (Figure 3).

Hypertension

160 (43.8%) individuals reported a history of hypertension. Still, it was found that during the study, almost half of the participants (49.3%) had hypertension, and nearly another half were in pre-hypertension (47.7%). Among those who reported that they knew their status, only 63.1% were regularly taking treatment. Adjusted prevalence ratios (aPR) indicated that being male was associated with a lower prevalence of hypertension (aPR: 0.54, 95% CI: 0.29 to 0.99, p=0.049), while older age (55 years and above) was associated with higher prevalence (aPR: 2.82, 95% CI: 1.78 to 4.51, p<0.001). 26 (7.1%) individuals reported diabetes prevalence, and 27 (7.4%) were newly diagnosed as having diabetes during the study.

DISCUSSION

This study used a non-laboratory method for the assessment of 10-year CVD risk using WHO risk prediction charts; previous studies on evaluation of concordance between laboratory and non-laboratory methods have shown that high concordance exists between results obtained by both methods, Das et al conducted a cross-sectional study in rural Ballabgarh, Haryana, India, involving 1,018 participants aged 30-69 years to assess the reliability of non-laboratory-based WHO cardiovascular disease (CVD) risk assessment charts; the study aimed to determine the concordance between non-laboratory-based and laboratory-based CVD risk charts and estimate the prevalence of selected CVD risk factors, their results showed a high concordance rate of 83.3% between the two types of charts. The sensitivity and specificity of the non-laboratory-based charts were 86.5% and 90.3%, respectively, using a 5% risk threshold. Their study concluded that non-laboratory-based WHO CVD risk assessment charts are suitable for estimating CVD risk in resource-limited settings like rural India, providing a reliable alternative to laboratory-based assessments. ¹⁵ Another study by Trideep and a group among the rural population in Lucknow has concluded that earlier available WHO/ISH risk prediction charts, which were available before WHO HEARTS risk prediction charts, were also feasible and valuable tools to predict CVD risk among asymptomatic individuals, and, such tools help in early detection and prevention of CVDs in resource-scarce settings.¹³ Initially, in our study, even though we had a laboratory component to study blood sugar and lipid levels, convincing the tribal community for blood drawing at the household and community level and transportation of blood samples from far off Islands to Port Blair was one of the challenges due to which this study was limited to use non-laboratory method only.

In this study, 58.9%, 31.2%, and 9.9% of the population were detected with low, moderate, and high CVD risk levels respectively, indicating that moderate and high CVD risk levels were high among Nicobarese tribes while compared with previous studies conducted in Northern and Southern parts of India.^12-14 This could be because a notable portion (66.8%) had a BMI ≥23.0 (indicating obesity), while 24.4% were smokers. Smokeless tobacco use was prevalent among 74.8%, and a substantial proportion (62.5%) reported alcohol consumption. Moderate to high CVD risk levels were associated with alcohol use (P=0.006) and lower levels of vegetable consumption (P=0.007). More than half of these tribes were classified as lower socio-economic status, and lower socioeconomic status was significantly associated with alcohol consumption and higher blood pressure levels. Our earlier reports from South Andamans on the general population have revealed that 32.4% and 5.8% of the rural population in the South Andaman Islands are at moderate and high CVD risk, respectively.¹⁹ It is found that Nicobarese have a higher level of moderate to high CVD risk scores compared to the general population in these groups of Islands, WHO HEARTS risk based CVD management tools has recommendations for management of CVD risk factors based on risk stratification levels and these tools can be adopted for risk reduction activities. ⁷

It is observed that 43.8% of individuals reported a history of known hypertension. Still, it was found that during the study, almost half of the participants (49.3%) had hypertension, and nearly another half of the participants were in pre-hypertension (47.7%) among those who reported that who knew their status, only 63.1% regularly taking treatment. One of our previous reports from South Andaman in the general population has shown that 48.1% were hypertensives, and among those who knew their status, only 63.41% were on regular treatment.²⁵ In this study, the reports are comparable to the burden of hypertension and status of taking regular treatment to hypertension; it could be because there is enculturation; and lifestyle risk factors including smoking, smokeless tobacco consumption, alcoholism, sedentary lifestyle exists among Nicobar tribes, and 14.8% self-reported that they consume excessive salt in their diet. Lower levels of fruit and vegetable consumption are observed among these tribes. The availability of vegetables and fruits in these Islands is a question that needs to be addressed as they depend on the frequency of ships that transport goods once a week or fortnightly. As a result, anecdotally, it is a known factor that prices of fruits and vegetables are high in these Islands.

One of the studies on oral lesions in the Nicobar Islands by A Rajkuwar et al has shown that there is a high prevalence of tobacco consumption (88.25%), especially the smokeless form of tobacco. They reported that oral mucosal lesions were present in 25.75% of the population, and keratosis was the most prevalent among oral mucosal lesions, at 56.3% and they have concluded that this high consumption of smokeless form of tobacco in the Nicobari tribal population increases the risk of developing precancerous and cancerous lesions in both genders.²⁶ Early intervention and oral health education should be done frequently to prevent the development of oral cancer at preliminary stages in this tribal population. ²⁶ Our reports are in the same agreement that higher levels of smokeless tobacco consumption are observed among both genders, and it requires an early intervention to prevent any morbid outcomes.

A report by Gopika et al on the status of cancer screening in India from the National Family Health Survey (NFHS)-5 report, has shown that the percentage of women who have ever undergone cervical cancer screening was only 1.9%; similarly one of our previous reports from South Andamans in the general population have shown that only 5.41% of women have undergone screening test for cervical cancer in their lifetime.^27,28 But in this current study, it is found that none of the women have undergone cervical cancer screening, and a population-based study on HPV infection and associated risk factors among South Andaman Islands conducted by Parvez et al has shown that the high prevalence of HPV as 5.9% and prevalence of HR-HPV16 was 4.1% and HR-HPV18 prevalence was 1.8%.²⁹ Therefore, it indicates to the health authorities and policymakers that cervical cancer screening activities are essential in these Islands.

CONCLUSION

Prediction of 10-year CVD risk levels shows moderate to high CVD risk levels are higher among Nicobarese tribes than reported levels among general populations. Illiteracy, lower level of educational status, consumption of alcohol, and low consumption of vegetables in the diet are the main predictors of such moderate to high CVD risk levels. NCD risk factors such as consumption of alcohol, smokeless tobacco, obesity, lower level of vegetable consumption, and excessive salt consumption are high among Nicobarese tribes. High prevalence of pre-hypertension, hypertension and its irregular treatment is a significant public health issue.

Recommendations

Immediate efforts to mitigate CVD risk levels should be undertaken along with attention to address elevated blood pressure levels and NCD risk factors including reduction of alcoholism, smokeless tobacco consumption, limiting salt intake and encouraging for regular physical activity. Public authorities should take appropriate measures to ease the availability of fruits and vegetables causing improvements in consumption levels in the tribal community, and measures for improving cervical cancer screening activities to be undertaken in these Islands.

ACKNOWLEDGEMENTS

We would like to thank the Tribal Council of Car Nicobar, Village Captains, ASHAs and ANMs of Car Nicobar Islands.

Funding: This research work is funded by ICMR (Indian Council of Medical Research) under Adhoc project sanctioned with letter no. No: 5/4/1-17/CVD/2022-NCD-I

Conflict of interest: None declared

Ethical approval: The study was approved by the Institutional Ethics Committee

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