Prevalence and associated factors for asthma in adults in Quito: a cross-sectional study

Abstract

Background:

Although several epidemiological studies of asthma have been carried out in Ecuador in the last two decades, none of these has estimated the prevalence of asthma in adult populations.

Objective:

To estimate the prevalence of asthma symptoms in adults in the city of Quito and to identify possible associated factors.

Methods:

A cross-sectional study was conducted on subjects older than 18 years residing in the Metropolitan District of Quito. The Global Asthma Network (GAN) questionnaire was applied to collect information on asthma symptoms and sociodemographic and lifestyle data. Bivariate and multivariate analyses with logistic regression were used to identify asthma-related factors.

Results:

2,476 subjects answered the questionnaire (80.9% women, mean age 40 years). The prevalence of wheezing in the last 12 months, asthma ever, and asthma diagnosed by a doctor were 6.3%, 1.9% and 1.6%, respectively. The prevalence of rhinitis ever and eczema ever was 13.7% and 5.5%. The presence of mould at home (OR: 2.13; 95% CI: 1.48 -3.06; p <0.001), cat at home (OR: 1.06; 95% CI: 1.06 -2.13; p <0.022) and rhinitis at some time (OR: 3.65; 95% CI: 2.53 - 5.29; p <0.022) were associated with the presence of wheezing in the last 12 months.

Conclusions:

Our study shows that, compared to other cities in Latin America, the prevalence of asthma in adults in Quito is relatively low. Along with the presence of rhinitis, factors related to housing quality are closely linked to the occurrence of asthma in adult populations.

Remark

1) Why was this study conducted?

In Ecuador, since 2003, the only study that has estimated the prevalence of asthma in adults was the World Health Survey. Since then, no study has updated the prevalence of asthma in the adult population in the country.

2) What were the most relevant results of the study?

Compared to other cities in Latin America, the prevalence of asthma in adults in Quito is relatively low. Factors related to housing quality are associated with the occurrence of asthma in adult populations.

3) What do these results contribute?

Our results allow comparing the prevalence of asthma in adults with previous studies conducted in the country and other countries in Latin America, as well as monitoring future trends in the prevalence of asthma.

Introduction

In the last decades, asthma has emerged as a significant challenge for health systems worldwide, affecting individuals of all ages ¹ . While the global prevalence of asthma is difficult to estimate because of a lack of up-to-date information and data gaps, the most recent global estimates suggest that 339 million people worldwide have asthma ² . Among those with asthma, children are most affected, and asthma is now the most common chronic disease of childhood ³ . However, although asthma prevalence in adults is relatively lower compared to children and adolescents, significant direct and indirect costs are associated with this condition through emergency visits, physician visits, diagnostic tests, among other social costs ⁴ .

Three major international studies (The European Community Respiratory Health Survey, The World Health Survey and The Global Allergy and Asthma Network of Excellence) have provided data on asthma prevalence in adults for comparisons between countries and regions ¹ . These studies have estimated that the overall prevalence of asthma in young adults (18-45 years old) is 4.3% but with vast differences between countries ⁵ . However, very little is known about the prevalence of asthma in middle-aged people and older adults, including the elderly ² , mainly because of the greater difficulty in distinguishing asthma from other respiratory conditions such as chronic obstruction from lung disease or chronic sinusitis ^{2 , 6} .

In Latin America (LA), the prevalence of asthma in adult populations has been rarely investigated ^{7 - 9} . However, estimations from countries that were part of The World Health Study (WHS) ¹⁰ showed that the prevalence of recent wheeze in adults ranged from 3.83% in Ecuador to 22.6% in Brazil. The prevalence of doctor diagnoses for asthma in these countries ranged from 2.0% in Ecuador to 12.0% in Brazil ⁵ . Since the WHS was conducted in 2003, few studies have estimated the prevalence of asthma in adults in LA. The objective of the present study was to estimate the prevalence of asthma symptoms in people over 18 years of age in the city of Quito and to evaluate possible associated factors.

Materials and Methods

Study Design

A cross-sectional study was conducted to estimate the prevalence of asthma symptoms in subjects over 18 years old in Quito, Ecuador. This study is part of the GAN initiative, and It was done between October 2018 to December 2019.

Study settings and population

Quito is the capital of Ecuador, a country with approximately 17,267,986 inhabitants (projection for 2019), a Human Development Index of 0.752 (ranked 86th in the world) and a gross national income per capita 11,350.00 PPP dollars. Quito, located at 2850 metres altitude, is the most populous city in Ecuador, with about 2.9 million inhabitants (projection for 2019) and a population density of 7,200 people living per km². The city has 156 public schools in the urban area, with approximately 134,000 students. The largest percentage of the population of Quito identifies itself as mestiza (80.6%), 12.8% as white, 3.3% as indigenous, and 3.1% as afro-Ecuadorian. Regarding the level of education, 2.7% of the population are illiterate, 30.9% have primary education, 39.7% have secondary education, and 26.7% have a university education. In the study area, the sex ratio is estimated at 100 women by 95 men ¹¹ .

This study is part of the project "Study of the prevalence of asthma and other allergic diseases in adolescents in Quito", and it is described elsewhere ¹² . The present study used information from the parents of adolescents who attended different educational units (public and private) of the Metropolitan District of Quito (MDQ).

Sample size

A total sample of 3,000 students was selected following the GAN guidelines ¹³ . A cluster sampling method was used to select 12 academic units (public and private) geographically distributed in the city. After this first stage, we selected all the students attending each school's ninth and tenth grades, which correspond to the student population of 13 and 14 years old. The eligibility criteria were: (i) children studying in the urban area of the MDQ and (ii) children between 13 and 14 years old. Each student was given an adult GAN questionnaire, which was to be filled out at home only by one representative of each adolescent (mother or father)

Data Collection

Questionnaires

The adult GAN questionnaire had a total of 42 self-administered questions. We evaluated demographic information such as sex, age, race/ethnicity and education. Several questions on asthma symptoms included breathing problems, wheezing in the past 12 months, wheeze attacks, speech problems, sleep problems, problems exercising, asthma ever, and asthma diagnosed by a doctor. Additionally, the instrument included questions on care for asthma as medical care during asthma attacks and medication for asthma. Lifestyle and home environment variables also were evaluated as moisture inside the house, mould inside the house, presence of large stains of moisture or mould inside the house, cat at home, dog at home, traffic around the house, smoking habits, smoking in the past, smoking habit in the present. The presence of allergic diseases (rhinitis ever and eczema ever) was included in the questionnaire. The outcome was defined as wheeze in the last 12 months (current wheeze).

Statistical analyses

A descriptive analysis was conducted to obtain frequencies and percentages of demographic, lifestyle, and asthma symptoms variables. Odds ratios (OR) were calculated using logistic regression to identify possible risk factors for current wheeze. In bivariate analyses, we associated each variable with current wheeze using logistic regression and p values <0.05 were considered statistically significant. Additionally, multiple regression analysis was used to find the best model. The final model was selected using back-wards step-wise regression and was that which explained the most variation in current wheeze prevalence, that with the smallest mean square error, and the highest value of adjusted R². Associations with p <0.05 were considered statistically significant. Data were analysed using the Software Package for Social Sciences (SPSS) version 24.0.

Ethics approval

This study was approved by the Ethics Committees of the Hospital Clinic de Barcelona (Reg. HCB/2016/0822) and by the Ethics Committees of the Hospital Carlos Andrade Marín in Quito. Additionally, the project was approved by the Ministry of Health and Education of Ecuador and the Directors of the selected schools. All parents/guardians were informed about the study in a face-to-face session, and those who agreed to participate signed a written consent form.

Results

Of a total of 3,000 questionnaires sent to parents or representatives, 2,476 were returned with the requested information, which means coverage of 82.5%. Table 1 shows the characteristics of the study population based on demographic and quality of life indicators. Around 81.0% of the study population were female, 60% had less than 40 years old, 92.9% were mestizo, and 60.9% of the population had secondary education. Rhinitis and eczema ever were reported by 13.7% and 5.5% of participants, respectively. Prevalence of wheeze in the last 12 months, asthma ever, and doctor diagnoses for asthma were 6.3%, 1.9%, and 1.6%, respectively (Table 2).

Table 1. Sociodemographic and lifestyle indicators of the study population.

Variables	Categories	n	%
Sex	Men	472	19.1
	Women	2,004	80.9
Age group (years)	21-30	136	5.6
	31-40	1,293	53.7
	41-50	750	31.1
	≥51	229	9.5
Ethnic group	Mestizo	2,299	92.9
	Others	177	7.1
Education	Primary	349	14.1
	Incomplete Secondary	419	16.9
	Completed Secondary	1,189	48
	University	517	20.9
Humidity at house	No	1,746	70.5
	Yes	730	29.5
Mould at house	No	1,985	80.2
	Yes	491	19.8
Smoking habit in the past	Never	1,917	77.4
	Seldom	453	18.3
	Daily	106	4.3
Smoking habit in the present	Never	2,179	88
	Seldon	248	10
	Daily	49	2
Traffic around the house	Never	201	8.2
	Seldom	962	39.2
	Frequently in the day	666	27.1
	Day and night	627	25.5
Cat at home	No	1,697	69.1
	Yes	759	30.9
Dog at home	No	726	29.6
	Yes	1,730	70.4
Rhinitis ever	No	2,138	86.3
	Yes	338	13.7
Eczema ever	No	2,340	94.5
	Yes	136	5.5

Table 2. Asthma symptoms .

Symptoms	Categories	n	%
Do you ever have trouble with your breathing?	Never	1,740	70.3
	Only rarely	550	22.2
	Repeatedly, but it always gets completely better	163	6.6
	Continuously, so that your breathing is never quite right	23	0.9
Have you had wheezing or whistling in your chest at any time in the past 12 months? (current wheeze)	No	2,320	93.7
	Yes	156	6.3
Have you had wheezing or whistling in your chest at any time in the past 12 months?	None	2,312	93.7
	1 a 3	126	5.1
	4 a 12	19	0.8
	More than 12	11	0.4
In the past 12 months, how often, on average, has your sleep been disturbed due to wheezing?	Never woken with wheezing	73	2.9
	Less than one night per week	56	2.3
	One or more nights per week	27	1.1
Have you ever been breathless when the wheezing noise was present?	No	66	2.7
	Yes	90	3.6
In the past 12 months, how often, on average, has your sleep been disturbed due to shortness of breath?	Never woken with wheezing	73	2.9
	Less than one night per week	60	2.4
	One or more nights per week	23	0.9
In the past 12 months, how often, on average, has your sleep been disturbed due to coughing?	Never woken with wheezing	51	2.1
	Less than one night per week	60	2.4
	One or more nights per week	45	1.8
Have you ever had asthma? (Asthma ever)	No	2,428	98.1
	Yes	48	1.9
Was your asthma confirmed by a doctor? (Doctor diagnosis of asthma)	No	2,437	98.4
	Yes	39	1.6

Table 3 shows the bivariate and multivariate analysis between wheeze in the last 12 months and demographic and lifestyle variables. Our results showed that women had 1.86 times more chance of wheeze compared to men (OR: 1.86; CI 95%: 1.13-3.08; p: 0.015), people who lived in homes with humidity had 1.99 times more chance of wheeze compared to those who lived in homes without humidity (OR: 1.99; CI 95%: 1.43-2.76; p: <0.001), people who lived in mold homes had 2.42 times more chance of wheeze compared to those who lived in mold-free homes (OR: 2.42; CI 95%: 1.72-3.42; p: <0.001), people who smoked daily in the past had 2.4 times more chance of wheeze than those who never smoked (OR: 2.4; CI 95%: 1.33-4.35; p: 0.004), people who smoke daily had 2.56 times more chance of wheeze than those who never smoked (OR: 2.56; CI 95%: 1.13-5.88; p: 0.024), people with a cat at home had 1.48 times more chance of wheeze than those without a cat at home (OR: 1.48; CI 95%: 1.04-2.02; p: 0.031), people with rhinitis and eczema ever had 4.31 and 2.61 times more chances of wheeze, respectively, than those without rhinitis and eczema (OR: 4.31; CI 95%: 3.04-6.10; p: <0.001) (OR: 2.61; CI 95%: 1.56-4.36; p: <0.001).

Table 3. Bivariate and multiple regression analyses between recent wheeze and sociodemographic and lifestyle variables.

Variables	Categories	Prevalence	Bivariate			Multivariate
		(%)	OR	95% CI	p	OR	95% CI	p
Sex	Men	3.8	1			1
	Women	6.9	1.86	(1.13-3.08)	0.015	1.57	(0.92-2.68)	0.096
Age group (years)	21-30	4.4	1
	31-40	7.3	1.7	(0.73-3.95)	0.219
	41-50	4.9	1.12	(0.47-2.71)	0.795
	≥51	6.6	1.51	(0.58-4.01)	0.399
Ethnic group	Mestizo	6.4	1
	Other	4.5	0.69	(0.33-1.42)	0.314
Education	Primary	5.4	1			1
	Incomplete Secondary	6.7	1.24	(0.68-2.26)	0.477	1.19	(0.63-2.24)	0.579
	Completed Secondary	5.5	1	(0.59-1.69)	0.987	0.95	(0.54-1.66)	0.867
	University	8.5	1.61	(0.92-2.81)	0.092	1.46	(0.81-2.65)	0.203
Humidity at house	No	5.0	1
	Yes	9.5	1.99	(1.43-2.76)	<0.001
Mould at house	No	5.0	1			1
	Yes	11.4	2.42	(1.72-3.42)	<0.001	2.13	(1.48-3.06)	<0.001
Smoking habit in the past	Never	5.9	1			1
	Seldom	6.2	1.04	(0.68-1.60)	0.85	0.99	(0.63-1.57)	0.993
	Daily	13.2	2.4	(1.33-4.35)	0.004	1.86	(0.93-3.70)	0.076
Smoking habit in the present	Never	6.1	1
	Seldom	6.5	1.06	(0.62-1.81)	0.829
	Daily	14.3	2.56	(1.13-5.8)	0.024
Traffic around the house	Never	6	1
	Seldom	5.9	0.99	(0.52-1.88)	0.98
	Frequently in the day	5.7	0.95	(0.48-1.86)	0.888
	Day and night	7.7	1.31	(0.67-2.51)	0.424
Cat at home	No	5.6	1			1
	Yes	7.9	1.48	(1.04-2.02)	0.031	1.51	(1.06-2.13)	0.022
Dog at home	No	6.7	1
	Yes	6.1	0.9	(0.63-1.28)	0.563
Rhinitis ever	No	4.6	1			1
	Yes	17.2	4.31	(3.04-6.10)	<0.001	3.65	(2.53-5.29)	<0.001
Eczema ever	No	5.9	1
Yes	14.0	2.61	(1.56-4.36)	<0.001

The multivariate analysis showed that people living in mould homes had 2.13 times more chance of wheeze compared to those living in mould-free homes (OR: 2.13; CI 95%: 1.48-3.06; p: <0.001), people with a cat at home had 1.51 times more chance of wheeze than those without a cat at home (OR: 1.51; CI 95%: 1.06-2.13; p: 0.022), and people with rhinitis ever had 3.65 times more chance of wheeze than those without rhinitis (OR: 3.65; CI 95%: 2.53-5.29; p: <0.001).

Discussion

The present study conducted a cross-sectional analysis to evaluate the prevalence of asthma symptoms in an adult population in Quito. Based on the GAN questionnaire, we estimated the prevalence of wheeze in the past 12 months, asthma ever, and doctor diagnosis of asthma for an adult population. Our results allow comparisons of the prevalence of asthma in adults with previous studies conducted in the country and other countries in the region and monitor future trends in asthma prevalence. Additionally, this study identified associated factors such as the presence of mould at home, pets at home (cat) and the presence of rhinitis, all of which are potentially modifiable.

In the last two decades, several studies have been conducted in Ecuador to estimate the prevalence of asthma and other allergic diseases ^{14 - 18} . However, all these studies have been conducted in child or adolescent populations. These studies have shown that the prevalence of asthma in the country varies between 10% and 20% ² . In the case of asthma studies in the adult population, the only study conducted in the country was the World health survey in 2003 ⁵ . This study showed that the prevalence of asthma diagnosed by a doctor for people over 18 years old was 2.03%, and the prevalence of wheeze symptoms was 3.8%. Our results showed that the prevalence of asthma diagnosed by a doctor is slightly lower (1.6%) than that reported by the WHS, and the prevalence of asthma measured by wheeze in the last 12 months was higher than that reported in the WHS. However, it is essential to emphasise that the definition of asthma symptoms in the WHS was based on the medical diagnosis of asthma, clinical asthma, and/or reported wheezing in the last 12 months, and our definition is based solely on those who presented wheeze in the last 12 months.

Few studies in LA have evaluated the prevalence of asthma in the adult population ^{5 , 8 , 9} . In Argentina, a study conducted in 2018 in subjects aged 20-44 years showed that the prevalence of asthma (defining asthma as the presence of exacerbations in the last year plus the use of medications), doctor diagnosed of asthma, and current wheeze was 5.9%, 9.5%, and 13.9%, respectively ¹⁹ . A study conducted in Brazil on patients older than 18 years showed that the prevalence of doctor diagnosis of asthma was 4.4% ²⁰ . In Mexico, a study in patients older than 40 years old showed that the prevalence of doctor diagnosis of asthma was 5% ²¹ . Another study conducted in Bogotá - Colombia, published in 2012, showed that the prevalence of doctor diagnosis of asthma in people aged 18 to 59 years was 6.3%, and the prevalence of current wheeze was 9.68% ²² . Comparing our results with the studies conducted in LA, we can observe that the prevalence of doctor diagnoses for asthma in Quito - Ecuador is relatively low.

Our study's relatively low prevalence of asthma could be related to several factors. First, active and passive smoking are known to be risk factors for asthma ²³ . However, an important positive environmental change experienced in Ecuador in the last years has been a decrease in the prevalence of cigarette smokers ²⁴ . According to the National Institute of Statistical and Census (INEC), cigarette consumption has gradually reduced in the country. In 1998, 9.5% of the Ecuadorians smoked daily; in 1999, 8.2%; in 2006, 5.0% and in 2014, 2.8% ²⁴ . There is also a much greater public awareness of cigarette smoke-related morbidities. Second, the low prevalence could be related to improvements and access to appropriate medical care. In the last two decades, a series of reform policies and processes increased the coverage of the population to social and health ²⁵ . These changes can be seen in the decrease in hospitalisations and mortality from asthma in Ecuador in the last two decades ²⁶ . Age-adjusted hospitalization rates decreased by 54.% from 2000-to 2018, from 278 to 129 per million population, and age-adjusted mortality rates decreased by 68% in the same period, from 11.1 to 3.5 deaths per million population. Third, in the last two decades, policies and regulations have been implemented in Quito to improve air quality. Because of air quality management and control, traffic-related air pollution has declined in Quito, a decrease that has been associated with a lower incidence of respiratory illness in the population ²⁷ . Finally, the low asthma prevalence could be related to new medications and medical care access and effectiveness. The latter is mainly represented by an increase in physicians in the country from 10808 in 2003 to 37293 in 2017 ²⁸ .

This study identified associated factors for asthma. Our results showed that people living in mouldy homes have more wheeze. The relationship between household environmental factors and asthma has been well documented ^{29 , 30} . Among the most important characteristics of the house related to asthma are the excessive humidity of the dwelling and the presence of mould ³⁰ . For example, a recent study conducted on the adult population in Sweden showed that people who lived in houses with mould and humidity had 5.72 times more asthma ³¹ . In our study, a part of the participants resided in the city centre, an area known for a high presence of old houses and colonial constructions. The age of the houses and their building materials could intensify the presence of allergic triggers such as mould, mites, cockroaches and others, increasing the prevalence of asthma. Likewise, our study showed that having a cat at home was associated with the presence of wheeze. It is well known that pets are an important source of household endotoxin. One study found that households with pets had an average of 1.4 times higher endotoxins concentrations in dust sedimented than households without pets ³² . Rhinitis was strongly associated with the presence of wheeze in our study population. It is widely known that rhinitis, sinusitis, and respiratory tract infections are frequently associated with asthma, regardless of the age of onset of the disease ³³ .

Approximately 81% of the study population was female, a factor associated with a higher prevalence of asthma in bivariate and multivariate analyses. The high presence of female participants in our study was because, in our environment, children's education falls on the mothers, so mothers generally filled out the questionnaires. The prevalence of asthma in women was double compared of men. This difference could be related to a higher representation of female participants in our study. However, several studies have shown that the prevalence, severity, rate of exacerbations, hospitalisations and mortality of asthma are higher among women than men populations ³⁴ . These differences could be related to sociocultural factors. For example, in our society, men are less likely to visit health services than women, increasing hospitalisation for asthma in women.

The main methodological limitation of our study is the non-random selection of the population. We worked with a convenience sample from another study. Other limitations of the study include its cross-sectional design and possible memory bias when using questionnaire data. Additionally, we could not evaluate the presence of atopy in the study population, so we could not estimate the associations between asthma symptoms and atopy, a relevant fact because non-atopic asthma is the most common form of childhood asthma in LA ^{35 , 36} .

Conclusions

The present study is one of the first investigations estimating the prevalence of asthma in adults in Quito. Our study shows that, compared to other cities in Latin America, the prevalence of asthma in adults in Quito is relatively low. Along with the presence of rhinitis, factors related to housing quality are closely associated with the occurrence of asthma in adult populations. Our results provide substantial evidence on the factors associated with the prevalence of wheeze symptoms in urban populations in LA.