Nguyen B. Chau

Abstract

In 2020, Hanoi and Ho Chi Minh City (HCMC), Vietnam’s biggest metropolitan cities rank 16^th and 11^th, respectively on the list of the world’s most polluted cities. Yet, the research body investigating the effects of exposure to air particulate matter (PM2.5 and PM10), which mainly contributes to air pollution, on Vietnamese’ psychological health is still scarcely populated. This research aims to fill this gap by using the Patient Health Questionnaire-9 (PHQ-9) and Generalized Anxiety Disorder-7 (GAD-7) to study the depression and anxiety levels of Vietnamese adults (n = 36) from Nha Be District (HCMC) with Air Quality Index (AQI) = 19 (good air quality), District 10 (HCMC) with AQI = 53 (moderate air quality), and Hanoi with AQI = 153 (unhealthy air quality) based on the scale of the United States Environmental Protection Agency (EPA). The study showed that participants from Hanoi scored higher than those from Nha Be and District 10 on both questionnaires. District 10’s participants also scored higher than those living in Nha Be District. However, results from the study also showed that air particulate matter level does not correlate with the severity (whether depression and anxiety symptoms affect participants’ daily lives) and the extent of those mental issues (from none to severe) in participants, while gender and age contribute to the high score of some individuals. This finding asks for heightened attention to Vietnamese living in highly polluted areas, especially impoverished regions where people do not have knowledge and access to healthcare under chronic exposure to air pollution.

Introduction

A large body of research has been conducted around the world on the effects of air pollution on humans’ physical conditions as indicated by the amount of air particulate matter 2.5 (PM2.5) and particulate matter 10 (PM10) – atmospheric mixtures of solid particles and liquid droplets with diameters less than 2.5 μm and 10 μm, respectively – in the air. Nevertheless, much less has been revealed about the impacts of such polluting agents on mental health and cognitive abilities.^[1] According to existing studies, particulate matter and ozone are among the most common and dangerous air pollutants concerning morbidity and mortality. The pathway of infection is through the hypothalamic-pituitary-adrenal (HPA) axis, which plays a critical role in responding to stressors (air pollutants in this case) through acute activation. However, chronic activation of the HPA axis may produce various consequences: increased risk of cardiovascular disease, metabolic dysfunction, depression, and reduced cognitive function.^[2] Another proposed pathway is inflammation involving the central nervous system (CNS). Neuroinflammation has been implicated as having an important role in the pathophysiology of both depression and psychosis.^[3]
In Vietnam, researchers have studied the harmful effects of air pollution on Vietnamese’ people and the risks of developing cardiovascular and respiratory problems. In such studies, they found that air pollutants (PM10, NO₂, SO₂) were positively associated with daily hospital admission for respiratory and cardiovascular diseases of the population in HCMC.^[4] Yet, like elsewhere in the world, there is also an alarming shortage in studies conducted on the correlation between the amount of PM2.5 and PM10 and potential psychological orders in Vietnam. Thus, this paper aims to fill this gap and reveals the consequences of constant exposure to PM2.5 and PM10 on Vietnamese adults who live in regions of low, moderate, and high AQI levels obtained from the Real-time Air Quality Index database.
We found that the high amount of particulate matter in the air correlates with the high depression and anxiety levels in participants, which supports our original hypothesis that air pollution does not only negatively affect human beings’ physique but also deteriorates our psychological system. To assess participants’ depression and anxiety levels, we used the translated PHQ-9 which was already used to measure depressive symptom severity in a Vietnamese population ^[5], and GAD-7 which was used previously to investigate the association of temporomandibular joint (TMJ) with Vietnamese’s anxiety and depression.^[6] Gender and age also play considerable roles in the differences in the mental health conditions of individuals. With these new findings, we propose that more efforts from the government be put into managing waste from industrial and agricultural practices that may contribute to air pollution and educating people from poor regions in Vietnam about the effects of this form of pollution on their mental health.

Method

METHODOLOGY
Study Participants: A total of 36 Vietnamese adults currently living in District 10 (Ho Chi Minh City), Nha Be District (Ho Chi Minh City), and Ha Noi participated in the study with 12 people representing each region. All participants are fluent in Vietnamese and have lived in their respective regions for at least 5 consecutive years. We divided each group into 3 age ranges: young adults (18 – 35 years old) (n = 16), middle-aged adults (36 – 55 years old) (n =15), and older adults (older than 55 years old) (n = 5) and 3 gender groups: male (n = 16), female (n = 20), and other (n = 0).
Areas: According to the EPA, the AQI value of an area is calculated based on four major air pollutants: ground-level ozone, particle pollution, carbon monoxide, and sulfur dioxide, ranging from 0 to 500 with particle pollution such as PM2.5 and PM10 making up a large portion. The quality of air is then classified into 6 groups based on the AQI value: Good (0 – 50), Moderate (50 -100), Unhealthy for Sensitive Groups (101 – 150), Unhealthy (151 – 200), Very unhealthy (201 – 300), and Hazardous (301 – 500). Based on the Real-time AQI database, AQI values of Nha Be, District 10, and Ha Noi are 19 (Good), 53 (Moderate), 153 (Unhealthy), respectively. Thus, these three regions were selected to represent different levels of air pollution in the two biggest metropolitans in Vietnam, Ho Chi Minh City, and Hanoi.
Assessment Questionnaires for Depression and Anxiety: Two questionnaires, PHQ-9 and GAD-7, were used to measure the level of depression and anxiety in participants. The raw score for both tests was calculated by adding up all the answers (0 – Not at all, 1 – Several days, 2 – More than half the days, or 3 – Nearly every day) for each question. The Vietnamese version of both questionnaires (already translated and retranslated to English for verification) was obtained from Canada’s Multicultural Health Care website. Both were conducted on Vietnamese people in previous studies and proved to be suitable for Vietnamese of all ages.

Fig. 2. The Vietnamese version of the PHQ-9 and GAD-7 obtained from Canada’s Multicultural Health Care website. A response of “Not at all” for any question will be counted as 0. A response of “Several days,” “More than half the days,” or “Nearly every day” will receive 1, 2, or 3 points, respectively. All the points will then be added up and classified correspondingly based on the PHQ-9 and GAD-7 scales.
Informed Consent: Each individual signed the informed consent form translated into Vietnamese by Pham Ngoc Thach University before participating in the study. Participants who live in Ho Chi Minh City completed the questionnaires on paper while participants from Ha Noi completed an online google form with informed consent. The online questionnaire was created so that every part was similar to that of the original questionnaire on paper.
Data analysis: From the PHQ-9, the total score of each participant was classified into 5 categories based on their raw scores: Minimal/None (0 – 4), Mild (5 – 9), Moderate (10 – 14), Moderately severe (15 – 19), and Severe (20 – 27). On the other hand, from GAD-7, participants’ scores were classified into 4 categories: None (0 – 4), Mild (5 – 9), Moderate (10 – 14), Severe (higher than 15). The data was then processed in Prism, a scientific 2D graphing and statistics software. Hypotheses were tested using the ordinary one-way and 2-way ANOVA hypothesis tests with standard p-value = 0.05.

Results

Effects of air particulate matter on depression and anxiety levels

The data shows that the presence of air particulate matter in areas with high air pollution level is directly correlated with the depression and anxiety levels of Vietnamese adults that participated in the study. Based on figure 3, there is not a correlation between depression level in District 10 participants and Nha Be participants. Nevertheless, there is a very strong correlation between the depression level in Ha Noi participants and Nha Be participants and the pollution level in each region: AQI = 153 and AQI = 19, respectively (p = 0.001*** on the ordinary one-way ANOVA test).

Fig. 3. Individual PHQ-9 score of participants in Nha Be District (AQI = 19), District 10 (AQI = 53), and Hanoi (AQI = 153) (n = 36). Participants from Nha Be District and District 10 completed the PHQ-9 on paper, while participants from Hanoi filled out the online form. The difference in air pollution does not have any correlation with the depression level in people from Nha Be and District 10 (p = 0.125 on the ordinary one-way ANOVA test). However, there is a very strong correlation between depression in participants in Nha Be and Hanoi and their respective air pollution levels (p = 0.001*** on the ordinary one-way ANOVA test).
Similarly, in figure 4 which presents the data from GAD-7, there is not a correlation between generalized anxiety level in Ho Chi Minh participants and Nha Be participants. However, there is a very strong correlation between the anxiety level in Ha Noi participants and Nha Be participants (p = 0.001*** on the ordinary one-way ANOVA test).

Fig. 4. Individual GAD-7 score of participants in Nha Be District (AQI = 19), District 10 (AQI = 53), and Hanoi (AQI = 153) (n = 36). Participants from Nha Be District and District 10 completed the GAD-7 on paper, while participants from Hanoi filled in the online form. The difference in air pollution does not have any correlation with anxiety levels in people from Nha Be District and District 10 (p = 0.556 on the ordinary one-way ANOVA test). However, there is a strong correlation between anxiety in participants in Nha Be District and Hanoi and their respective air pollution levels (p = 0.001*** on the ordinary one-way ANOVA test).

The extent and severity of depression and anxiety in different regions

At the end of the survey, there is a question asking the participant “If you check off any problems, how difficult have these problems made it for you to do your work, take care of things at home, or get along with other people” translated into Vietnamese for the use of Vietnamese people. Four levels of difficulty indicate the extent to which the depressive or anxiety symptoms they chose affect their daily lives. From figure 5, there is no correlation between the extent of mental health issues and where the participants currently live. No participants found it very difficult or extremely difficult to carry out daily chores while having such symptoms. There are more participants from Nha Be finding it “not difficult at all” to go about their normal lives than those from Hanoi, but District 10 has the highest number of participants finding that it is “somewhat difficult” to carry out all the tasks.

Fig. 5. The extent to which depression and/or anxiety symptoms made it difficult for participants to do daily work, take care of things at home, or get along with other people. At the end of the questionnaire, participants chose the level that described the difficulty with which depression and/or anxiety have interfered with their daily activities. There is not a significant correlation between air pollution level (where Hanoi is the most polluted, Nha Be the least) and the impacts of depression and/or anxiety on subjects’ daily lives (n = 36, p > 0.05 on the 2way ANOVA test). The 4 colored boxes represent the extents to which participants are affected, which corresponds with the colors of boxes on the graph.
For the PHQ-9, levels of depression in participants are divided into five categories with scores from 1 to 27 (the higher the score, the more severe depression is). On the other hand, for theGAD-7, levels of anxiety in participants are divided into four categories with scores from 0 to 21 (the higher the score, the more severe anxiety is). On both tests, participants in Hanoi showed all levels of depression and anxiety as in figures 6 and 7. Statistically, however, there are no correlations found between the amount of air particulate matter from the three regions and the severity of depression/ anxiety in participants.

Fig. 6. Classification of depression level based on raw scores of participants from three regions. The total score of each participant in the PHQ-9 was calculated by adding up their answers to each question in the test, which was then classified into 5 categories. The graph shows that participants from Hanoi underwent all degrees of depression, from mild to severe while those in Nha Be District had minimal/none to mild depression. Statistically, the 2way ANOVA test does not show any correlation between air pollution and the severity of depression in participants (p > 0.999). The 5 colored boxes represent 5 different levels of depression, which correspond with the colors of boxes on the graph.

Fig. 7. Classification of anxiety level based on raw scores of participants from three regions. The total score of each participant in the GAD-7 was calculated by adding up their answers to each question in the test, which was then classified into 4 categories. The graph shows that participants from Hanoi underwent all degrees of anxiety, from none to severe while all Nha Be’s participants did not have any anxiety whatsoever and District 10’s participants underwent none to mild anxiety. Statistically, the 2way ANOVA test does not show any correlation between air pollution in different areas and the severity of anxiety in participants (p > 0.999). The 4 colored boxes represent 4 different levels of anxiety, which correspond with the colors of boxes on the graph.

The effects of gender on depression/ anxiety level of participants in different regions

In total, 16 males and 20 females participated in the study. From the PHQ-9, there is a moderate difference between the score of male participants from Nha Be District and those from Hanoi (p = 0.040) with males from Hanoi scoring higher. There is no correlation between males from District 10 versus those from other regions. On the other hand, there is no correlation between the depression levels of female participants from all three regions. In figure 8, the mean for females’ scores in each region is higher than that of the males. However, there exist overlaps between males’ and females’ score in each region that prevent a definite conclusion about the effects of gender on depression level.

Fig. 8. PHQ-9 scores of male and female participants from Nha Be District, District 10, and Hanoi. The total score of each participant in the PHQ-9 was calculated by adding up their answers to each question in the test and then classified into male (n = 16) and female (n = 20) groups. There is a statistically significant correlation between the depression level of male participants from Nha Be District and those from Hanoi (p = 0.040*). Female participants were represented with purple dots and male participants were represented with black dots.
From the GAD-7, there is a moderately strong correlation between the score of male participants from Nha Be District and those from Hanoi (p = 0.017). There is no correlation between males from District 10 versus those from other regions. On the other hand, there are strong correlations between females from Hanoi and those from District 10 and Nha Be, separately. Females from Hanoi score much higher than the GAD-7 than their counterparts in the other two regions. Nevertheless, there is no correlation between those in District 10 and Nha Be. In figure 9, the mean for females’ scores in each region is higher than that of the males. However, there are also overlapping regions that prevent a definite conclusion about the effects of gender on anxiety level.

Fig. 9. GAD-7 scores of male and female participants from Nha Be District, District 10, and Hanoi. The total score of each participant in the GAD-7 was calculated by adding up their answers to each question in the test and then classified into male (n = 16) and female (n = 20) groups. There is a statistically significant correlation between the anxiety level of male participants from Nha Be District and those from Hanoi (p = 0.017*). Among female participants, there is a very strong correlation between the anxiety level of those from Nha Be and those from Hanoi (p = 0.008*) as well as those from District 10 and those from Hanoi (p = 0.003*). Female participants were represented with purple dots and male participants were represented with black dots.

The effects of age on depression/ anxiety level of participants in different regions

Participants belong to three age groups: young adults (18-35 years old) (n=16), middle-aged adults (36-55 years old) (n =15), and older adults (older than 55 years old) (n=5). From the PHQ9 data presented in figure 10, there is a strong direct relationship between the PHQ-9 test score of young adults in Nha Be and in Hanoi (p = 0.003**) and between middle-aged adults in these two regions (p = 0.002**). Furthermore, there is a very strong correlation between the score on this test from middle-aged adults in District 10 and those from Hanoi (p <0.001***).

Fig. 10. PHQ-9 scores of participants in 3 different age groups. The total score of each participant from the PHQ-9 was calculated by adding up their answers to each question in the test and then classified into young adults (18-35 years old) (n=16), middle-aged adults (36-55 years old) (n =15), and older adults (older than 55 years old) (n=5). According to the 2way ANOVA test, there is a significant correlation between the depression level of young adults in Nha Be District and Hanoi(p = 0.003**). Among middle-aged adults, there is a correlation between those from Nha Be District and Hanoi (p = 0.002**) and between those from District 10 and Hanoi (p < 0.001***). Young adults were represented with red dots, middle-aged adults black, and older adults blue.
From figure 11, a strong correlation is found between GAD-7 scores of young adults from Nha Be and those from Hanoi (p = 0.002**) with those from Hanoi scoring much higher than from Nha Be. On the other hand, middle-aged adults from Nha Be and Hanoi also have a correlation where the score increases for those living in Hanoi with higher amounts of particulate in the air.
No correlation whatsoever among older adults in the three regions in both tests were detected.

Fig. 11. GAD-7 scores of participants in 3 different age groups. The total score of each participant from the GAD-7 was calculated by adding up their answers to each question in the test and then classified into young adults (18-35 years old) (n=16), middle-aged adults (36-55 years old) (n =15), and older adults (older than 55 years old) (n=5). According to the 2way ANOVA test, there is a significant correlation between the anxiety level among young adults in Nha Be District and Hanoi (p = 0.002**). Among middle-aged adults, there is also a correlation between those from Nha Be District and Hanoi (p = 0.045*). Young adults were represented with red dots, middle-aged adults black, and older adults blue.

Discussion

 Findings:

The study shows that the higher the air particulate matter is, the higher the depression and anxiety levels are in Vietnamese adults from Ho Chi Minh City and Hanoi. While the score itself was affected, the extent and degree of such stress-related illnesses were not affected by the difference in the amount of particulate matter in the three regions. The correlation in this study corroborates with an observational study conducted in China, which found that short-term air pollution worsens mental health and depression symptoms in families and individuals from 162 counties in 25 provinces of China who participated in the survey.^[7] Another study in Spain also revealed that higher exposition to different air pollutants (particularly to PM10) is associated with a more frequent history of depression.^[8]
There is a correlation between males from Nha Be and those from Hanoi in both tests, but there is only a correlation between women from Nha Be versus Hanoi and District 10 versus Hanoi in the GAD-7 test. No correlation exists between the sample from District 10 and that from Nha Be.
Out of the three age groups, young adults, and middle-aged adults from Nha Be and Hanoi do share strong correlations with one another on both tests. Furthermore, there is also a very strong correlation between middle-aged adults from District 10 and Hanoi in the PHQ-9. No relationship is found between older adults in any group against one another. This also happened with a study conducted in America, which did not find a positive association between short-term changes in pollutant levels such as PM2.5 and depressive symptoms in a cohort of geriatric adults (age ≥ 65 years).^[9] A definitive conclusion was not reached on whether age was a factor in the different test scores on the PHQ-9 and GAD-7. In this study, the number of older adults (n = 5) was significantly smaller than that of the other two age groups (n = 15 and n = 16), so it might lead to the inability of Prism to generate any relationships between the groups.
The fact that there is not much correlation between the data set from District 10 and Nha Be District may stem from the fact that these two regions are both in Ho Chi Minh City. This leads to the possibility of citizens in two districts sharing the same atmosphere. People who report living in either district can also travel to the other frequently since they are not far away from one another. Furthermore, the insignificant difference may also be because the extent of pollution between the two regions is not stark enough to effect a change in mental health. Thus, choosing another region in a further area from Ho Chi Minh City such as Hue or Danang (Central Vietnam) with more striking differences in their AQI level may improve the final conclusions.

Limitations:

Firstly, the sample of this study is small (n = 36) so the results are not representative of the whole country and may not be the same if this was conducted on a larger scale in different regions other than just Nha Be, District 10, and Hanoi. Secondly, the form for Hanoi participants is online due to restrictive traveling during the COVID-19 season, which may lead to some participants not taking it as seriously as they would on paper. Thirdly, there are a lot of factors that are not controlled and recorded in this experiment such as participants’ upbringing, individual socioeconomic status, particular events during the testing period that adds to the stress, etc. The fact that Nha Be District is a less developed area in the city than District 10 and Hanoi – the heart of the country and a major industrial hub is not enough. Fourthly, the AQI index of different areas in one district can be strictly different from one another. Hanoi has 36 towns, each of which may have a very different air pollution status. Fifthly, as this research study was conducted during the summer of 2020 when the COVID-19 pandemic undoubtedly put some more stress on every individual, especially those from Hanoi with a lot of cases, it may skew the results presented above relatively.

Potential for future projects:

This experiment could be improved by gathering larger sample sizes with an equal number of participants in each region and from a wide range of age groups, which could help prevent the effects of confounding variables. To eliminate any possible discrepancies between the online question form and paper form, future experiments can use a uniform form and ensure that all participants take it under the same conditions (preferably in person). As the AQI level can change in a matter of days or weeks, it should be controlled in each small region in a more selective and careful manner so that the results are credible. Furthermore, future researchers can add a question at the end of the survey about the opinions of participants about the air pollution in the neighborhood where they live so as to attain a more accurate view of the variable.

Conclusion

This study adds another layer to the scarce amount of research done on the influences of air pollution on the depression and anxiety levels of Vietnamese. It confirms that there is a direct correlation between the amount of air particulate matter that contributes to air pollution and the mental health of Vietnamese adults in District 10, Nha Be District, and Hanoi. Especially with two regions that have starkly different AQI levels, Hanoi and Nha Be, there is a very significant difference between the depression and anxiety levels in people living in those regions. This calls for more care and attention to those who are living in polluted regions as air pollution can be one of the main factors that affect not only human physical conditions but also mental health. Given the alarming pollution status in Vietnam, it is of utmost importance that air pollution solutions be implemented by the government, locals, and citizens, and crucial knowledge about this correlation be spread effectively to Vietnamese in different regions. For future research, the air pollution level and mental health of people living in less developed areas of Vietnam such as the Northern Mountains and Central Highlands, the poor who are not aware of the exposure to air particulate matter that they are under, should be investigated.

Acknowledgments

The author is truly grateful for the guidance of Dr. Huong Thanh Thi Ha (Stanford University) through every step of this research project. I would also like to thank Dr. Ha’s teaching assistants, which include Ms. Quynh My Ngoc Nguyen and Mr. Thinh Quoc Van Tran for always responding to my inquiries and helping me refine my study. I want to thank Ms. Anh Hoang Phuc Le for guiding me through the use of Prism and offering advice on how to create informative and accurate figures. Special thanks to Mr. Luan Van Tran for refining my paper and constantly looking for ways to make it better after each revision. I also want to thank Ms. Caressa Hanh Truong for readily offering help along the way when any difficulties arise and for introducing me to Dr. Huong Ha so I can learn about her ongoing research projects in the field.
This would not have been possible without the help of Ms. Trang Mai Luu, Ms. My Tra Duong, Ms. Tram Quynh Thuy Nguyen, and Mrs. Chau Quynh Thi Bui for providing me with contacts of participants from Hanoi when I did not get access to them due to travel restrictions during COVID-19.
I also want to thank all the participants in my study from Nha Be District, District 10, and Hanoi for your enthusiasm and cooperation. Despite the challenging conditions during COVID-19, you have given me the consent to carry out this study and followed up with you after the questionnaires.
I also want to acknowledge Ms. Trang Quynh Nguyen and Ms. Nam Thi Thu Nguyen for translating the PHQ-9 and GAD-7 to Vietnamese for future studies. You have inspired me to further investigate mental health issues in different populations in Vietnam, given how studies in this field are especially scarce due to the lack of measurement tools (e.g. scale for depression level) that Vietnamese can understand and use. Final thanks go to Canada’s Multicultural Health Care Center for publishing the translated versions of PHQ-9 and GAD-7 into Vietnamese for public use on their website, which I used for this study’s purpose.

Appendix The English version of the PHG-9 and GAD-7 questionnaires

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About the author

Nguyen (Audrey) Chau is from Vietnam and is currently an undergraduate student at Princeton University, NJ. She was awarded the 2018’s Lawrence S. Ting Scholarship by her high school Saigon South International School (SSIS) for a strong commitment to academic excellence and a willingness to serve others. She is also the co-founder of Vietnam’s first Brain Bee competition and president of the environmental club at SSIS. Audrey is currently interested in Abnormal Psychology and Environmental Studies.