What are the Impact of Season and Temperature Variations in India on the Number of Adolescent/Adult Mortality Due to Heart Disease / Hypertension – A Cross-Sectional Research Study?

Background/Rationale

One of the researchers of this study who is also a medical doctor with experience of 18 years has suspected that there are season and temperature variations in India on the number of adolescent/adult mortality due to Heart disease / Hypertension. During regular duties at various Government hospitals, the researcher felt some trends in the title-mentioned research question. Hence the researcher decided to investigate the query mentioned in the title with proper evidence and accredited data. The key purpose is to alert the policy-makers, caregivers, medical doctors, patients, decision-makers, researchers, and citizens of India, etc through evidence-based study to take proper care during the seasonal and temperature variations which may harm persons suffering from Heart disease / Hypertension.

There are several research studies done on the impact of season and temperature on hypertension and related mortality which established that a relationship exists between them. For example, a cross-sectional analytic research study on the impacts of seasonal differences on blood pressure extents in children, adolescents, and young adults prepared by Miersch A, et al. [1] found a noteworthy seasonal variation in blood pressure (BP) measurements. This research study found that the mean increase in systolic/ diastolic blood pressure during the winter season was 4.45/2.42 mmHg respectively. This research study also found that an important correlation exists between outdoor temperature and systolic BP [1]. These studies have also prompted the researcher to investigate the title-mentioned research question. Climatic conditions are now a well-known factor that can influence cardiovascular health established through several research studies [2]. Some research studies had also revealed that cardiovascular disease-related morbidity and mortality usually increase during winter which is attributed to several physiological alterations during winter necessary for protecting the body from cold such as a rise in sympathetic activity, change in the blood coagulation profile, endothelial dysfunction, and rise in blood pressure (BP) [3]. Few research studies have shown that BP increases with a decrease in temperature [4]. The climatic conditions are considerably different in different geographical locations, and this is also influencing other diseases such as COVID-19 in India [5, 6]. Several population-based research studies were done about factors affecting seasonal variations in BP such as one done by Goyal A, et al. [7]. One review paper on seasonal patterns of twelve cardiovascular diseases found that there is a seasonal trend in cardiovascular disease (CVD) incidence with the highest numbers of cases in the colder winter months, in many countries [8]. Another research study done by Sinha P ET alia found that the prevalence of hypertension (HTN) in summer is lower in comparison to winter months [9]. Continuous ongoing changes in the global climate can also affect the epidemiology of HTN and also the epidemiology of CVD. One multicenter research study in central China done on the impact of temperature on life loss per death from CVD found that both cold and hot temperatures can cause premature death from CVDs [10].

Despite being the second-most populous country of the world with wide variations of seasons/temperature, the researcher has not found any adequate broad country- based study conducted in India for evaluating the impact of temperature / seasonal variation on the number of adolescent/adult mortality due to Heart disease / Hypertension in the general population. In the light of the above-mentioned truths and facts, we conducted an HMIS (health management information system) -based cross sectional observational research study with accredited data from 36 states and union territories of India including mortalities from all public/private/rural and urban health facilities of India registered with HMIS of MoHFW (Ministry of Health and Family Welfare) [11].

CVDs (Heart Diseases) are the most important cause of death accounting for 17.9 million people’s mortality globally in 2019, representing 32% of all global mortalities; of which 85% were caused by heart attack and stroke [12]. Hypertension is a serious medical condition of elevated blood pressure that increases the risks of heart diseases; 1.28 billion adults globally have HTN and two-thirds (66%) of these are living in low- and middle-income countries (LMICs) like India [13]. According to WHO (World Health Organization), HTN is diagnosed if, when it is observed on two different days that the systolic blood pressure (SBP) measurement on both days is ≥140 mmHg and/or the diastolic blood pressure (DBP) readings on both days is ≥90 mmHg.

Study Design

This research study was a Country / HMIS (MoHFW) accredited data-based retrospective cross-sectional study conducted across all HMIS registered public/private/rural and urban health facilities of 36 states and UTs (union territories). The Geographical latitude and longitude division according to temperature/season and analysis of the impact of season and temperature variations on the mortality trends of adolescents/adults due to Heart disease / Hypertension across 36 states and union territories of India will be performed in the next versions.

Enlistment of the HMIS registered public/private/ rural and urban health facilities mortality across 36 states and union territories of India were started in January 2018 Winter season (January - February) and were followed for 4 seasons: Winter Season Jan-Feb, Pre-Monsoon Season Mar-May, Monsoon Season Jun-Sep, Post-Monsoon Season Oct-Dec(°C). These divisions of the season - months were based on observed temperature/season variation in different months in India according to the apex body Indian Meteorological Department (IMD) established for this purpose in the country. On an average temperature basis, the coldest months were Winter Season Jan-Feb, whereas Monsoon Season June to September was registered as the hottest months of the year according to the IMD data.

Setting

This research study evaluated the impact of season and temperature on the prevalence of mortality of adolescents/ adults due to Heart disease / Hypertension across 36 states and union territories of India during the study period i.e. 1st January 2018 to 31st December 2020. This research study examined/investigated a total of 941153 mortality of adolescents/adults due to Heart disease / Hypertension across 36 states and union territories of India during 36 continuous months of study from 1st January 2018 to 31st December 2020. Microsoft office and Stata15.1 software were used for data collection and analysis from HMIS of MoHFW. The researcher feels that more years’ data should be utilized for such studies and this will be available in the next version with 10 plus years of data analysis research.

Participants

Eligible participants were any adolescent/adult who died due to Heart disease / Hypertension in any public/ private/rural/urban health facilities registered on the HMIS database of MoHFW across 36 states and union territories of India during the study period i.e. 1st January 2018 to 31st December 2020. A total of 941153 eligible subjects’ mortalities were included in this research study on an all- India basis. The study population for this novel research study consisted of any adolescent (10 to 19) / adult (19 and above) mortality due to Heart disease / Hypertension across 36 states and union territories of India of both the sexes.

Ethical Considerations

Ethical approval was not applicable as this research study has not done any human or animal trials etc. or involved them in such a way that requires ethical approvals. Added

Meteorological Data

to this, the data utilized is available to the public and we had not disclosed any hidden or secret data. The purpose of this research study is well explained above, and ethical approval is not applicable for such studies in India based on data available in the public domain. The researcher is a medical doctor working for the government of Bihar, India and this research study is a part of the author’s independent self- financed research.

Variables

The key variables for this research study were the meteorological variables data from IMD and mortality data from HMIS which are enlisted below in Tables-1, 2, 3, and 4.

Table1: All India Mean Seasonal Temperature (°C) and statistical analysis of temperature data.

Mortality Data

Table2: Number and statistical analysis of total Adolescent / Adult deaths due to Heart disease / Hypertension related in different months and years.

Data Sources/Measurement

Temperature data were collected from IMD whereas the mortality data were collected from HMIS. Measurements were done with the help of Microsoft Office and Stata15.1 software to find out the impact of season and temperature on the prevalence of mortality of adolescents/adults due to Heart disease / Hypertension across 36 states and union territories of India.

Bias

Data from consecutive three years were utilized to reduce the bias. Further, mean temperature for different seasons and mean for other variables were compared for bias reduction. In the next version, more years will be studied for bias reduction and generalizability.

Study Size

A total of 941153 eligible subjects’ mortalities were included in this research study on an all-India basis, see table-2 for details.

Quantitative Variables

See Tables – 1, 2, 3, and 4.

Statistical Analysis

The data was analyzed by Microsoft Office and Stata15.1 statistical software. Data were calculated as mean ± standard deviation as well as 95% C. I (confidence interval) and standard errors etc. were also calculated with the help of original data, see tables-1, 2, 3, 4, and 5 for quantitative variables. Comparisons of mortalities among the four seasons with different mean temperatures were done and results are described in words and charts, see charts – 1, 2, 3, 4, and 5.

Meteorological Data Analysis Results

The mean temperature (degree Celsius) ± standard deviation recorded in Winter Season Jan-Feb (°C), were 20.91 ± .29, with 95% Conf. Interval 20.20 - 21.62, Std. Err. .16, Min 20.71, and Max 21.24; The mean temperature (degree Celsius) ± standard deviation recorded in Pre-Monsoon Season Mar-May(°C), were 27.91 ± .30,, with 95% Conf. Interval 27.17 - 28.66, Std. Err. .17, Min 27.58, and Max 28.16; The mean temperature (degree Celsius) ± standard deviation recorded in Monsoon Season Jun-Sep(°C), were 28.44 ± .16,, with 95% Conf. Interval 28.05 -28.84, Std. Err. .09, Min 28.28, and Max 28.6; The mean temperature (degree Celsius) ± standard deviation recorded in Post-Monsoon Season Oct-

Dec(°C) were 23.59 ± .14,, with 95% Conf. Interval 23.26 - 23.93, Std. Err. .08, Min 23.49 and Max 23.75 see Table-1 and Figure-1.

Total Adolescent / Adult Deaths Due to Heart Disease / Hypertension Related In Different Months and Years Analysis Results

A total of 941153 eligible subject’s mortalities that died due to Heart disease / Hypertension related causes were analyzed during the 36 month observational study period. The analysis of monthly variations of eligible subject’s mortalities that died due to Heart disease / Hypertension are shown for different months of different years and combined all years in Table-2 and Figure5.

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2020 – Monthly /Seasonally Analysis of Mortalities of Adolescent /Adult Deaths Due to Heart Disease / Hypertension

The total number of mortalities observed during 12 months of 2020 from Heart disease / Hypertension were 318391; Mean- 26532.58;Max / month – 32496; Min / month – 19683 and no. of Obs-12. Heart disease / Hypertension mortalities were highest in Sep-20(32496) followed by Aug- 20-(29995) and Jan-20(29560) while lowest mortalities were found in Apr-20 (19683). The mean seasonal mortality for Heart disease / Hypertension mortalities were highest in post monsoon (mean temperature 23.75°C) having mean mortality 29127.33followed by Winter Season Jan-Feb (mean temperature 20.79°C) with mean mortality 27885.5 , monsoon (mean temperature 28.45°C) with mean mortality 27826.5 and pre monsoon (mean temperature 27.58°C) having lowest mean mortality 21310.67See table-1, 2, and 4; figure-2. The change may be due to COVID-19 impact which is found to be having negative impact on Heart disease / Hypertension.

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2019 – Monthly /Seasonally Analysis of Mortalities of Adolescent /Adult Deaths Due To Heart Disease / Hypertension

The total number of mortalities observed during 12 months of 2019 from Heart disease / Hypertension were

316637; Mean- 26386.42;Max / month – 30511; Min / month – 24068 and no. of Obs-12. Heart disease / Hypertension mortalities were highest in Jan-19(30511) followed by Sep- 19-(28196) and Aug-19(26730) while lowest mortalities were found in Apr-19 (24068). The mean seasonal mortality for Heart disease / Hypertension mortalities were highest in Winter Season Jan-Feb (mean temperature 20.71°C)

having mean mortality 28618 followed by post monsoon (mean temperature 23.49°C) with mean mortality 26510.67, monsoon (mean temperature 28.6°C) with mean mortality

26333 and pre monsoon (mean temperature 28°C) having lowest mean mortality 24845.67. See tables 1, 2, and 4; figure 3.

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2018 – Monthly /Seasonally Analysis of Mortalities of Adolescent /Adult Deaths Due to Heart Disease / Hypertension

The total number of mortalities observed during 12 months of 2018 from Heart disease / Hypertension were 306125; Mean- 25510.42;Max / month – 29346; Min / month – 22365 and no. of Obs-12.Heart disease / Hypertension mortalities were highest in Jan-18(29346) followed by Feb-

18-(27581) and Dec-18(27467) while lowest mortalities were found in Apr-18 (22365). The mean seasonal mortality for Heart disease / Hypertension mortalities were highest in Winter Season Jan-Feb (mean temperature 21.24°C) having mean mortality 28463.5 followed by post monsoon (mean temperature 23.55°C) with mean mortality 26737, monsoon (mean temperature 28.28°C) with mean mortality 24434 and pre monsoon (mean temperature 28.16°C) having lowest mean mortality 23750.33 See tables 1, 2, and 4; figure 4.

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Figure 4: Monthly mortalities of Adolescent /Adult deaths due to Heart disease / Hypertension. 2018-2019-2020-Combined –Analysis of Mortalities of Adolescent /Adult Deaths Due to Heart Disease / Hypertension Combined 2018-2019-2020 - Monthly / seasonally-The three years of study when combined together shows that the Heart disease / Hypertension mortalities were highest in January with 89417 mortalities ([95% CONF. INTERVAL] 84795.48 - 94038.52 ; STD. ERR.-1074.109; MEAN- 29805.67; STD. DEV.-620.1374; MIN-29346; MAX-30511 followed by September-85633 (95% CONF. INTERVAL- 57391.89 - 113874.1)and December-83682 (95% CONF. INTERVAL -73045.63 - 94318.37) while lowest mortalities were found in April – 66116 (95% CONF. INTERVAL- 49641.4 - 82590.6 ). The mean seasonal mortality for Heart disease / Hypertension mortalities were highest in Winter Season Jan-Feb (mean temperature 20.91°C) having mean mortality 28322.33 followed by post monsoon (mean temperature 23.59°C) with mean mortality 27458.33, monsoon (mean temperature 28.44°C) with mean mortality 26197.83 and pre monsoon (mean temperature 27.91°C) having lowest mean mortality 23302.22, See tables 1, 3, and 4; figures 5 and 6.

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Figure 6: Combined mean mortality of study period in different seasons. The total numbers of observations of mortality due to Heart disease / Hypertension were thirty six (36- one per month; 12 per year) and 12 for mean temperatures during different seasons, see tables 1, and 2. The total numbers of mortalities observed were 941153 (STD. ERR.-16325.48; [95% CONF. INTERVAL] 908010.5- 974295.5; Mean 26143.14; Std. Dev.-2720.914; Min 19683; Max 32496). The 95% confidence interval of total data mean was [95% Conf. Interval] 25222.51 - 27063.76 with standard error 453.4856.