Influence of seasonal changes on asthma exacerbation in a sudan savanna region: An analysis of 87 cases.

Background: Asthma accounts for 1 out of every 250 deaths worldwide. Many of these deaths are preventable as they occur as a result of suboptimal long-term medical care and delay in seeking help during severe exacerbation. It is believed that increased concentrations of dust, high winds, low temperatures, and low humidity may cause exacerbation of asthma. Objective: The aim of this study is to assess seasonal variation in asthma exacerbation among patients attending Usmanu Danfodiyo University Teaching Hospital, Sokoto. Materials and
Methods: Eighty-seven patients aged 16 years and above with physician-diagnosed asthma were selected by systematic random sampling. Clinical information was obtained from each participant about history of asthma exacerbation and health-care utilization. Meteorological data were obtained from the Nigerian Meteorological Agency corresponding to period of patient's recruitment.
Results: Eighty-seven patients comprising 60 females and 27 males aged 32.1 ± 10.8 years participated in the study. Among the study participants, 50.6%, 28.7%, and 20.7% had exacerbation during harmattan, rainy, and dry (hot) seasons, respectively. Correlation analysis shows a significant negative relationship between temperature and asthma exacerbation (r = -0.372, P < 0.01).
Conclusion: This study shows that asthma exacerbation is most frequent during the harmattan season and low temperature is associated with its exacerbation.

INTRODUCTION

Asthma exacerbations are associated with increased emergency department visits and hospitalizations with attendant increased cost of health care and mortality.[1] About 250,000 deaths worldwide are attributed to asthma yearly and most of these deaths are preventable as they arise from suboptimal asthma control and delay in seeking help during severe attack.[2] In Nigeria, mortality rate from acute severe asthma ranges between 4.9% and 6%.[3]

Asthma attack may be precipitated by indoor allergens (house dust mite, molds, pets, and cockroaches), outdoor allergens (pollens and outdoor molds)[4] and nonallergenic triggers such as viral infections, active and passive smoking, air pollution, occupational exposures, drugs such as nonsteroidal anti-inflammatory drugs and beta-blockers, emotional disturbances, and seasonal changes. Seasonal variation of asthma exacerbations has been reported.[56] There were reported cases of increase in the number of children with asthma exacerbation during September, which also coincides with school return.[7]

The influence of weather on morbidity and mortality due to asthma exacerbation varies with age. Therefore, while children and young adults show autumnal peak in asthma morbidity and a summer peak in mortality, elderly individuals (65 years and above) have greater asthma morbidity and mortality in the winter.[89] For instance, in Nigeria, studies done in South-Western part of the country showed asthma admissions to have seasonal pattern.[101112]

Sokoto is located in the Sudan Savanna region of Nigeria. It has three distinct seasons that includes harmattan (November–February), the hot (March–May), and wet (June–October) seasons.[13] Harmattan period is characterized by dry, cold, and dusty wind during which the temperature may drop to < 20°C in some cases. The mean annual rainfall is about 200 mm with most of it falling in July and August.[13]

Several risk factors such as exercise, emotional stress, air pollution occupational exposures, and seasonal changes have been associated with asthma exacerbation, and prevention of asthma exacerbation has been established as an important component in achieving asthma control.[14] The current long-term goal of asthma management anchors on sustained and effective control of asthma symptoms and minimization of future risk of exacerbations. It is, therefore, important to evaluate the impact of seasonal changes on asthma exacerbation in every region. Furthermore, there is a paucity of data on the impact of seasonal changes on asthma exacerbation in northern Nigeria. This study tends to shed light on the influence of environmental weather conditions in relation to exacerbation and severity of asthma attacks, hoping that the outcome would provide data for planning asthma care and effective control of asthma symptoms.

MATERIALS AND METHODS

This was a cross-sectional retrospective study conducted between 1st February 2016, and January 2017. The study population consisted of asthma patients seen and managed at the medical outpatient (MOP) clinic and Accident and Emergency (A/E) Department of Usmanu Danfodiyo University Teaching Hospital (UDUTH), Sokoto, on account of asthma exacerbation.

A total of 87 patients were recruited for the study after obtaining informed consent. Inclusion criteria included adults aged 16 years and above with physician-diagnosed asthma presenting with asthma exacerbation. Exclusion criteria were current or past history of cigarette smoking and those with comorbid conditions such as pulmonary embolism, chronic obstructive pulmonary disease, and congestive cardiac failure.

A systematic random sampling[15] method was used in selecting patients. Patients at A/E were interviewed after they received treatment for asthma exacerbation and were comfortable to be interviewed. A structured researcher-administered questionnaire adapted from the Behavioral Risk Factor Surveillance System/Asthma Survey Questionnaire[16] was used as an instrument of data collection. A diagnosis of asthma exacerbation was established when a patient with physician-diagnosed asthma presented with progressive shortness of breath, cough, wheezing, or chest tightness. The questionnaire was pretested among 10 selected patients with asthma at MOP Department of Specialist Hospital, Sokoto, as a pilot study before proceeding with the study. This allowed confirmation of suitability, timing, and feasibility of the questionnaire.

Data for temperature, humidity, wind, and rain on the dates of recruitment of the patients were obtained from the Nigerian Meteorological Agency (NIMET), Sokoto. At the agency, temperature was recorded in degree centigrade using a dry bulb thermometer and daily maximum and minimum air temperatures were recorded. Relative humidity was recorded at the agency using a dry and wet bulb thermometer. Maximum daily humidity was recorded at 19 h’ local time and minimum humidity recorded at 07-hour local time. Humidity was recorded as percentage (%). Rainfall was collected using rain gauge and subsequently transferred to measuring cylinder for measurement and was measured in milliliter (ml). Wind velocity was measured in meter per second using a cup counter anemometer. All data collected were used to determine the relationship with asthma exacerbation in relevant participants.

Statistical analysis

The data were recorded and analyzed using Statistical Package for Social Sciences, software version 20. Spss Inc. IBM Corporation, Chicago, Illinois, USA. Categorical data such as sex and occupation were presented as frequencies and percentages, while numeric data such as age and body mass index were presented as mean and standard deviations. Pearson's correlation analysis was used to define relationship between weather variables and asthma exacerbation. All statistical tests were carried out with level of significance set at 0.05.

Ethical consideration

Approval was obtained from the Ethics and Research Committee of UDUTH. Informed consent was obtained from the participants involved in the study and all information obtained was treated with utmost confidentiality. The cost of carrying out the study was borne by the researcher. All procedures complied with 2013 Helsinki declaration.

RESULTS

A total of 87 patients were recruited for the study, 27 (31.0%) male and 60 (69.0%) female. The response rate was 100%. The sociodemographic characteristics of the study participants are shown in Table 1. The mean age of the participants was 32.1 ± 10.8 years. Majority of the patients (39.1%) were in the age group of 20–29 years. Occupation of the participants revealed that 32.2% were in the civil service, while 29.9% were unemployed and 25.3% were students.

Table 1

Sociodemographic characteristics of participants

Characteristics	n=87
Age, mean±SD	32.1±10.8
Age group (years), n (%)
≤19	7 (8.0)
20-29	34 (39.1)
30-39	25 (28.7)
40-49	14 (16.1)
50-59	5 (5.7)
≥60	2 (2.3)
Sex, n (%)
Male	27 (31.0)
Female	60 (69.9)
Ethnicity, n (%)
Hausa	61 (70.1)
Yoruba	7 (8.0)
Ibo	6 (6.9)
Fulani	9 (10.3)
Others	4 (4.6)
Occupation, n (%)
Student	22 (25.3)
Civil service	28 (32.2)
Trading	6 (6.9)
Unemployed	26 (29.9)
Farming	5 (5.7)

SD=Standard deviation

Clinical characteristics of participants

The clinical characteristics of the participants are shown in Table 2.

Table 2

Clinical characteristics of participants

Characteristics	n (%)
Frequency of symptoms within the last 30 days
None	16 (18.4)
1-10	42 (48.3)
10-20	16 (18.4)
20-30	13 (14.9)
Symptoms all the time?
Yes	23 (26.4)
No	64 (73.6)
Times symptom affect sleep within the last 30 days
None	24 (27.6)
1-5	41 (47.0)
>5	22 (25.1)
Symptom-free days within the last 2 weeks
None	27 (31.0)
1-5	26 (29.9)
>5	34 (39.1)
URTI
Yes	49 (56.3)
No	38 (43.7)
Routine clinical checkup times
None	58 (66.7)
1-5	23 (26.4)
>5	6 (6.9)
BMI (kg/m2)	26.99±5.58

URTI=Upper respiratory tract infection, BMI=Body mass index

Majority (42; 48.3%) of participants had frequency of symptoms 1–10 within the last 30 days and most (41; 47%) had their sleep affected by asthma symptoms in the range of 1–5. Most participants, 49 (56.3%), had upper respiratory tract infection and 58 (66.7%) never attended routine clinical checkup, and 18.4% patients who had no symptoms over the last 30 days presented with asthma exacerbation.

Seasonal distribution of asthma exacerbation

Figure 1 shows monthly distribution of patients with asthma exacerbation. The highest number was seen in the month of February (16 patients) and December (13 patients), while the lowest was seen in October (1 patient).

Figure 1

Seasonal distribution of asthma exacerbation

Distribution of number of asthma exacerbations in various seasons

Table 3 shows the number of exacerbations in various seasons. Among patients who had exacerbations during rainy season, 10 (40%) had one exacerbation, while 4 (16%) each had 3 and 4, respectively. During harmattan season, 14 (31.8%) patients had 2 exacerbations, while 2 (4.6%) and 4 (9.1%) had seven and eight exacerbations, respectively. It is worthy of note that 1 (2.3%) patient had 10 exacerbations during harmattan season.

Table 3

Distribution of number of asthma exacerbations in various seasons

Number of exacerbations	Recruitment seasons
	Rainy, n (%)	Hot, n (%)	Harmattan, n (%)
1	10 (40)	1 (5.6)	5 (11.4)
2	5 (20)	5 (27.8)	14 (31.8)
3	4 (16)	4 (22.2)	10 (22.7)
4	4 (16)	4 (22.2)	5 (11.3)
5	2 (8)	4 (22.2)	3 (6.8)
7	0	0	2 (4.6)
8	0	0	4 (9.1)
10	0	0	1 (2.3)

Relationship of meteorological parameters and asthma exacerbation

The relationship of meteorological parameters and asthma exacerbation is shown in Table 4.

Table 4

Relationship of meteorological parameters and asthma exacerbation

Weather variable	Minimum	Maximum	Mean±SD	Correlation (r)	P
Temperature	21.5	36.0	29.02±4.20	−0.372	<0.001
Humidity	8.7	95.6	26.85±20.88	0.137	0.206
Rain	0.00	36.2	0.92±4.61	−0.072	0.509
Wind	0.02	319.6	84.45±85.23	−0.041	0.709

SD=Standard deviation

There was strong negative correlation between temperature and asthma exacerbation (mean = 29.02, r = −372, P ≤ 0.001). Humidity, rainfall, and wind speed did not influence asthma exacerbation.

DISCUSSION

Seasonal circles of asthma exacerbation requiring hospital treatment have been shown in many countries.[14] Most patients with asthma exacerbation seen in this study were seen during harmattan season with the highest peak being in February and a trough in October. A second smaller peak was seen in June, which corresponded to a month in the rainy season. Similarly, individual patients were found to experience higher number of recurring exacerbations in harmattan season. These findings are similar to a study done in Kano by Uduma,[17] which showed increased prevalence of asthma during harmattan season. They attributed their findings to changes in temperature and the chemical constituents of harmattan dust. Similarly, seasonal variation in hospital admissions for asthma has also been shown by Grech[18] in Malta who showed admissions to be highest in January, corresponding to winter period in that region. The findings, however, contrast the studies done in South-Western part of Nigeria.[1119] Desalu in Ido-Ekiti[11] and Akinyemi in Ile-Ife[19] observed that bronchial asthma was more common in wet season than in dry season.

High humidity, cold and dry air, and hot humid air have all been listed as common asthma triggers.[20] Harmattan period is characterized by dry, cold, and dusty wind during which the temperature may drop to <20°C.[13] During this period, people tend to stay more indoors with windows and doors closed especially at night. They also lit fires indoors using wood or charcoal in order to keep warm. Thick clothes are worn and thick blankets are used to cover the body at night. These behavioral changes encourage transmission of respiratory viral infections, increase close contact with house dust mite, and other indoor triggers of asthma exacerbation such as biomass. These might explain the high proportion patients with asthma exacerbation during harmattan season in the current study.

Furthermore, a significant negative correlation was demonstrated between temperature and asthma exacerbation. This supports the findings of Akinyemi both in Ile-Ife and Ilorin.[19] He observed negative correlation between air temperature and bronchial asthma. Similar findings were also demonstrated by Rossi in Finland.[21] Akinyemi attributed his findings to drops in temperature during wet season, which could lead to increase in sympathetic activity, elevation in plasma noradrenaline, activation of the renin–angiotensin system, and alteration in blood hemostasis, such as the increase in plasmin in addition to hypercoagulability. However, unlike the findings of Akinyemi and Rossi, no significant relationship was demonstrated in this study between humidity and asthma exacerbation. The difference between the findings of Akinyemi and that of this study might be because while Ile-Ife is situated in humid forest zone with an annual rainfall exceeding 1500 mls and very high relative humidity, Sokoto is situated in dried Savanna region.

The low annual rainfall and relative humidity coupled with the short period of rainy season recorded in this study might have accounted for the difference in our findings. Furthermore, no significant relationship between asthma exacerbation and wind speed is found in this study. This is similar to the findings of Akinyemi[19] in Ile-Ife and Ilorin but contrasts that of Depradine[22] in Barbados who found negative correlation between wind speed and asthma exacerbation.

CONCLUSION

The study demonstrated seasonal variation in asthma exacerbation with most patients presenting during harmattan season. Asthma exacerbation also demonstrated inverse relationship with temperature. As a preventive measure of asthma exacerbation, patients should be counseled to avoid precipitating factors, especially during harmattan season. Health-care planning in human and material resources is required to take care of high burden of exacerbation of asthma during harmattan season. Assessment of the chemical and microbial contents of harmattan dust and assessment of indoor air quality was not done in the study and this is suggested for further study.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.