Advances in Human Biology

ORIGINAL ARTICLE
Year
: 2019  |  Volume : 9  |  Issue : 2  |  Page : 162--167

Epidemiology, incidence and mortality of thyroid cancer and their relationship with the human development index in the world: An ecology study in 2018


Elham Goodarzi1, Alireza Moslem2, Hossein Feizhadad3, Alireza Mosavi Jarrahi4, Hossein Ali Adineh5, Malihe Sohrabivafa6, Zaher Khazaei7,  
1 Department of Public Health, School of Public Health, Social Determinants of Health Research Center, Lorestan University of Medical Sciences, Khorramabad, Iran
2 Department of Public Health, Iranian Research Center on Healthy Aging, Sabzevar University of Medical Sciences, Sabzevar, Iran
3 Department of Microbiology, Infectious and Tropical Diseases Research Center, Health Research Institute, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran
4 Department of Epidemiology, Faculty of Health Sciences, Simon Fraser University, BC, Canada
5 Department of Epidemiology and Biostatistics, Iranshahr University of Medical Sciences, Iranshahr, Iran
6 Department of Public Health, Student Research Committee, Dezful University of Medical Sciences, Dezful, Iran
7 Department of Epidemiology, School of Public Health, Ilam University of Medical Sciences, Ilam, Iran

Correspondence Address:
Zaher Khazaei
Department of Epidemiology, School of Public Health, Ilam University of Medical Sciences, Ilam
Iran

Abstract

Objective: Thyroid cancer is one of the most common malignancies, with an incidence rate of about two fold in the last 25 years and accounting for 2% of all cancers. The Human Development Index (HDI) is used to measure the development of countries level. The aim of this study was to investigate thyroid cancer morbidity and mortality and its association with HDI. Methods: The present analysis is a descriptive cross-sectional study that is based on cancer incidence data and cancer mortality rates extracted from the World Bank for Cancer in 2018. The incidence and mortality rates and thyroid cancer distribution maps were drawn for world countries. To analyse data, correlation and regression tests were used to evaluate the correlation between incidence and mortality with HDI. The statistical analysis was carried out by Stata 14, and significance level was estimated at the level of 0.05. Results: The results showed a positive correlation between incidence and thyroid cancer (r = 0.497, P < 0.05); however, the correlation observed between mortality and HDI was negative, which was not statistically significant (r = −0.06, P > 0.05). There was a positive and significant correlation between incidence with gross national income per 1000 capita (r = 0.328, P < 0.0001), Mean years of schooling (r = 0.445, P < 0.0001) life expectancy at birth (r = 0.509, P < 0.0001) and expected years of schooling (r = 0.463, P < 0.0001); however, this correlation was not statistically significant in mortality rate (P > 0.05). Linear regression model showed that increase in LEB (B = 0.2, confidence interval [CI] 95%: [0.01, 0.4]) significantly increased thyroid cancer incidence (P < 0.05). The regression analysis showed that increase in life expectancy at birth (B = 0.02, CI 95% [0.008, 0.04]) increased mortality (P < 0.05). The study showed that the mean incidence and thyroid cancer mortality in female were significantly higher than males (P < 0.05). Conclusion: The thyroid cancer incidence in high-HDI countries and the mortality rate in countries with low HDI are increasing. Therefore, HDI can be used to provide a clear picture for the distribution of this cancer in different parts of the world.



How to cite this article:
Goodarzi E, Moslem A, Feizhadad H, Jarrahi AM, Adineh HA, Sohrabivafa M, Khazaei Z. Epidemiology, incidence and mortality of thyroid cancer and their relationship with the human development index in the world: An ecology study in 2018.Adv Hum Biol 2019;9:162-167


How to cite this URL:
Goodarzi E, Moslem A, Feizhadad H, Jarrahi AM, Adineh HA, Sohrabivafa M, Khazaei Z. Epidemiology, incidence and mortality of thyroid cancer and their relationship with the human development index in the world: An ecology study in 2018. Adv Hum Biol [serial online] 2019 [cited 2019 Dec 12 ];9:162-167
Available from: http://www.aihbonline.com/text.asp?2019/9/2/162/257811


Full Text



 Introduction



Thyroid cancer is one of the most common malignant endocrine glands worldwide.[1],[2] Papillary and follicular cancers make up 90% of thyroid cancer.[3],[4] It is estimated that thyroid cancer prevalence is 1%–5% in female and 2% in male, and it is the 7th most common cancer in female and the 14th in male. According to the American Cancer Association, by 2014, 62,980 new cases of thyroid cancer have been diagnosed, most of which are in female and in individuals under the age of 65. The main reasons for this difference in female than male are polymorphism role in female oestrogen receptors.[5],[6],[7] Oestrogen also significantly increases the amount of cell proliferation in cancerous thyroid cells compared to the male hormone.[7],[8] The most common age of thyroid cancer affliction is seen in the fifth and sixth decades of life.[9] Initial manifestations of this cancer are single or multiple thyroid nodules, lymphadenopathy around the neck and voice violence.[10],[11] Cancer comprises a range of clinical symptoms from high differentiation and favourable prognosis to unprotected anaplastic malignant neoplasia, which is often seen in the elderly.[12] Gender (female), age, weight, diabetes mellitus, obesity, height and body mass index, exposure to ionising radiation, use of levothyroxine, tumour size, pregnancy, lifestyle, weather conditions,[12],[13] genetic factors, underlying thyroid disease, hormonal factors (more prevalence in female) and nutritional factors (especially iodine) play an important role in thyroid cancer pathogenesis.[14],[15] Since the 1990s, thyroid cancer incidence has risen in most developed countries, such as the United States, Canada, France and Australia, and has doubled. The reports also confirmed the incidence of cancer in Asians.[16],[17],[18],[19] It is possible that this increase in the number of thyroid cancer cases is due to the improvement of diagnostic methods or further exposure to unknown risk factors.[20],[21] Therefore, due to the nature and numerous factors affecting thyroid cancer, increasing the number of new cases, especially in female, and the increased mortality rate caused by this cancer around the world, this study was designed to evaluate thyroid cancer morbidity and mortality and its association with the Human Development Index (HDI) of societies in 2018.

 Methods



Due to limitations in quality and existing cancer data coverage worldwide, especially in low- and middle-income countries, it is necessary to be cautious in interpreting these data. The IARC approach is not just to evaluate, compile and use data from other institutions, but the intention is to work with country centres to improve the native data quality, data coverage and analytical capacities. The urgent need for investment in population-based cancer data coverage in low- and middle-income countries led to Global Cancer Registry Programme (GICR) launch in collaboration with the IARC. The GICR's aim is to provide cancer control data, which can be regularly promoted through the coverage, quality and use of world population-based cancer data. A summary of the steps used to calculate the incidence of cancer, its mortality and prevalence is presented below. The calculation methods vary from country to country, and the quality of the national computing data depends on the coverage, accuracy, time of the outbreak and the mortality rate of each country.

Incidence

The methods used to calculate the incidence rate associated with gender- and age-related cancer in each country, in order of priority, fall into the following broad categories:

The reported national incidence rate was announced by 2018 (45 countries)The newest observation rates (national or regional) for the population were applied in 2018 (50 countries)The rates were calculated using national mortality data with modelling and the mortality ratio of the cancer record in that country (14 countries)The rates were calculated using national mortality using modelling, mortality rate and incidence of cancer recording in neighbouring countries (37 countries)National incidence rates for age and gender for all cancers were obtained by averaging the overall rates of neighbouring countries. Subsequently, these levels were partitioned to produce a national incidence for each specific site using the relative frequency of cancer data (7 countries)Rates were calculated as an average of selected neighbouring countries.

Mortality

The methods used to calculate mortality rates associated with gender- and age-related cancer in each country, in order of priority, are categorised into the following general categories:

The nationally monitored mortality rate was announced by 2018 (81 countries)The latest observed national mortality rates were applied for the population in 2018 (20 countries)Rates were calculated using data from the methodology associated with modelling assistance, as well as the proportion of mortality to the obtained prevalence of cancer record in neighbouring countries (81 countries)Rates were calculated as an average of selected neighbouring countries (3 countries).[22],[23]

Human Development Index

HDI is a composite index of three-dimensional indicators: life expectancy, study rates and mastery of the resources needed to have a decent life. All the groups and regions that have made significant progress on all HDI components have grown faster than those with low or medium HDIs. As the indicator shows, the universe is unequal because national averages do not show different experiences of people's lives. There are countless inequalities in the northern and southern countries, and income inequalities have increased in each country and between the different countries.[24],[25],[26]

 Results



The cancer registrations in 2018 show 18,078,957 new cases with 9,555,027 mortalities, of which 567,223 new cases (3.31%) and 41,071 (0.46%) died due to thyroid cancer. The highest thyroid cancer incidence was in the Asia continent with 340,245 (60%) cases, and the lowest was in the Oceania continent with 4999 (0.88%) cases. The highest mortality rate was also found in the Asia continent with 23,847 cases (58.1%), and the lowest was in the Oceania continent with 308 cases (0.75%) [Figure 1].{Figure 1}

[Table 1] shows thyroid cancer incidence and mortality rate in different countries. The study showed that the highest thyroid cancer incidence in the world was in the Republic of Korea (60.7 per 100,000), Cyprus (21 per 100,000) and Canada (19.5 per 100,000). The highest thyroid cancer mortality rate was related to Vanuatu (2.8 in 100,000), Samoa (6.2 in 100,000) and Papua New Guinea (1.8 in 100,000) [Figure 2].{Table 1}{Figure 2}

Based on the cancer registries in 2018, the highest incidence (11.7 per 100,000) is related to very high-HDI areas, and the highest mortality rate (0.48 per 100,000) is related to medium-HDI areas [Figure 3].{Figure 3}

The variance analysis results showed that the highest average thyroid cancer incidence (9.3 per 100,000) was related to very high HDI and the lowest (1.6 per 100,000) was connected to low HDI with a statistically significant difference (P < 0.0001). The highest mean mortality (0.54 per 100,000) was documented in medium HDI, and the lowest (0.41 per 100,000) was in very high-HDI countries without statistically significant difference (P > 0.05) [Table 1].

The study showed that there is a positive and significant correlation between incidence and thyroid cancer (r = 0.497, P < 0.05). The correlation between mortality rate and HDI index showed a negative correlation which was not statistically significant (r = −0.06, P > 0.05) [Figure 4].{Figure 4}

A positive and significant correlation was seen between incidence with GNI (r = 0.328, P < 0.0001), MYS (r = 0.445, P < 0.0001), LEB (r = 0.509, P < 0.0001) and EYS (r = 0.463, P < 0.0001), but this correlation was not statistically significant for mortality (P > 0.05) [Table 2].{Table 2}

Linear regression model showed that increase in LEB (B = 0.2, confidence interval [CI] 95%: [0.01, 0.4]) significantly increased the thyroid cancer incidence (P < 0.05). In addition, analysis of regression results showed that increase in LEB (B = 0.02, CI 95% [0.008, 0.04]) increased mortality (P < 0.05) [Table 3].{Table 3}

The study results showed that thyroid cancer, mean incidence and mortality rates in female were significantly higher than males (P < 0.05) [Table 4].{Table 4}

 Discussion



The average of thyroid cancer mortality rate has increased by 50% in the world from 99 in 1990 to 92 in 2010, with the highest mortality rate compared to other endocrine cancers.[27]

A total of 298,102 new cases of thyroid cancer (66,179 males and 229,923 females) with 39,771 deaths were recorded worldwide in 2012. The standardised incidence and mortality rate of thyroid cancer were 4 and 0.5 per 100,000, respectively. Of these, 14,719 cases were in high-HDI countries and 11,188 in low-HDI countries. The highest incidence was in high HDI and highest mortality was in low- and moderate-HDIs countries. A positive and significant correlation was seen between the standardised incidence of thyroid cancer and the HDI. A negative and significant correlation was also seen between thyroid cancer standardised mortality rate and HDI. Highest incidence rate thyroid cancer was occurred in high-HDI countries and the highest mortality rate in low- and moderate-HDIs countries.[28]

The number of 298,102 new cases of thyroid cancer was recorded in 2012. The incidence rate ranged from 1.3 per 100,000 per year in low-HDI countries to 9.9 per 100,000 in high HDIs. The number of diagnosed cases in female was higher than male (77.1% vs. 29.9%). Furthermore, thyroid cancer mortality rate in female was 2.5 times higher than male. The most important reasons for it could be the difference in hormonal, reproductive and fertility factors.[29]

The study documented 18,078,957 new cases of thyroid cancer with 9,555,027 deaths in 2018. The highest and lowest incidence and mortality rates of thyroid cancer were in the Asian and Oceania continents, respectively. There was a positive and significant correlation between the HDI and thyroid cancer incidence. The correlation between mortality and HDI was negative, which was not statistically significant. A significant and positive correlation was between incidence rate and HDI dimensions without significant correlation in mortality rate. Increasing LEB led to a significant increase in thyroid cancer incidence and mortality rates. The mean of thyroid cancer incidence and mortality rates in female is significantly higher than males.

In the last few decades, the increasing incidence of thyroid cancer was reported in many countries except African countries (due to inadequate diagnosis).[3] The main causes of thyroid cancer progression are unknown, but geographical, racial, ethnic, environmental and nutritional factors play a significant role in it.[10]

In confirmation of the study results, previous studies have also shown that increased thyroid cancer is affected by socioeconomic status and the extent of community development. In fact, thyroid cancer incidence varies from country to country and is related to the HDI so that its prevalence in male ranges from 79 per 100,000 in West Africa to 365 per 100,000 in Australia and New Zealand. The incidence rate in female similarly increased from 103 per 100,000 in Central and South Asia to 295 per 100,000 in North America. Thus, it can be said that in developed countries, people have a higher level of knowledge about thyroid cancer and exercise seriously physical examinations at an earlier age of life. They also have better access to healthcare and advanced thyroid cancer diagnostic techniques.[30] The increased life expectancy is one of the main causes of increased thyroid cancer in developed countries which facilitates the occurrence of certain diseases such as cancers because individuals are longer exposed to potentially harmful thyroid cancer factors.[30]

Therefore, increasing the age and increasing the aging population is an unfavourable prognostic factor in thyroid cancer.[31] Furthermore, in developed countries, people are increasingly faced with environmental factors such as ionising radiation, cosmic radiation, pesticides and carcinogenic solvents. Exposure to some chemicals during uterus life and childhood, increased autoimmune thyroid disease, overweight, obesity, alcohol and smoking are among the other risk factors that are found in developed and developing countries[32],[33] often which in these areas, benign thyroid disease is high prevalent, a known risk factor for thyroid cancer.[34]

This is while the death rate in high HDI is lower than poorer countries or with the less HDI. In various studies, it is confirmed the relationship between HDI and its dimensions with community's health. In countries with low HDI, diagnosis is the final stage of illness because of less access to health care. Thus, in low-HDI societies, inadequate socioeconomic support is associated with a variety of adverse health outcomes for individuals and justifies additional cancer burden, less survival and other adverse effects of cancer.[35] So that, the mortality rate in male ranges from 132 per 100,000 in very high-HDI countries to 87 per 100,000 in low-HDI countries. Overall, cancers are one of the three leading causes of mortality in the world, and about 70% of deaths from cancer occur in low-HDI countries.[36],[37]

 Conclusion



In recent years, thyroid cancer incidence has increased faster than other malignancies in both genders, which is more pronounced in female than male. Mortality is higher in low-HDI countries than developed countries which have dramatic social consequences. Therefore, having a general picture of thyroid cancer, epidemiological features are effective in preventing, diagnosing and early treating to reduce its mortality.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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