Open Access

Factors associated with health-related quality of life in adults with asthma. A cross-sectional study

  • Francisco-Javier Gonzalez-Barcala1Email author,
  • Ramon de la Fuente-Cid2,
  • Mónica Tafalla3,
  • Javier Nuevo3 and
  • Francisco Caamaño-Isorna4
Multidisciplinary Respiratory Medicine20127:32

https://doi.org/10.1186/2049-6958-7-32

Received: 2 May 2012

Accepted: 25 July 2012

Published: 2 October 2012

Abstract

Background

The measurement of health-related quality of life (HRQoL) is increasingly recognized as an important endpoint, as a reflection of the effects of the disease from a patient perspective. Our aim was to evaluate the factors determining the HRQoL in patients with asthma, according to the EQ-5D questionnaire.

Methods

Patients were included using multi-stage sampling, from Primary Care clinics from all the Autonomous Communities in Spain. The patients included were: over 18 years-old, with a confirmed diagnosis of asthma for at least one year, and had visited a Health Centre in the previous 2 years. The characteristics of the asthma disease, the adherence to treatment, the socio-demographic variables, the smoking habits, and the asthma control were collected using a questionnaire. The influence of the different variables included in the study on the EQ-5D was evaluated using multivariate logistic regression analysis.

Results

A total of 2,125 patients were finally included (57.7% females, mean age 48 years). The response rate was 95.4%. Some factors showed a considerable detrimental effect on the HRQoL of asthmatics. Advanced age, lower educational level and poor control of asthma are significantly associated with a worse quality of life in all the dimensions assessed by the EQ-5D scale. The baseline severity of the asthma, and having been admitted to hospital are related to a worse quality of life in 5 of the 6 dimensions analyzed.

Conclusion

In our study, we could identify some factors related to quality of life in asthma patients. The most important were advanced age, lower education level, and poor control of the asthma.

Keywords

Asthma Quality of life Risk factors Adults

Background

The measurement of health-related quality of life (HRQoL) is increasingly recognized as an important endpoint, a reflection of the effects of the disease from a patient’s perspective. It covers a multidimensional concept, not only associated with the disease itself and the medical actions developed for its management, but also with the physical, social and psychological functioning of the patient [15]. Although clinical and physiological parameters are needed to evaluate the disease, these are not sufficient to understand and assess how the patients perceive their state of health [6, 7].

It is known that asthma negatively influences the quality of life of the patients who suffer from it, but the determining factors are not fully understood. In fact, the most severe forms of the disease are associated with a worse quality of life, but this relationship is not linear [8, 9]. The factors related to this aspect of the disease need to be identified in order to improve the quality of life of the patients [79]. Several questionnaires have been developed to assess HRQoL. Some are used for specific diseases, while others are generic [7].

The EuroQol-5D (EQ-5D) questionnaire is a generic tool for measuring HRQoL, applicable in healthy individuals as well as in patients with a specific disease, which seems to have demonstrated validity and reliability in asthma [7]. In this, five health dimensions, stratified into 3 levels, as well as visual analogue scale (VAS) are descriptively evaluated [7].

The EQ-5D is a generic HRQoL questionnaire, and although not specific for asthma, it is considered valid for cross-sectional population studies of patients with this disease [2].

Our aim was to evaluate the factors associated with HRQoL in patients with asthma, from a multidimensional perspective.

Methods

Patients were included, using multi-stage sampling, from Primary Care clinics from all the Autonomous Communities in Spain. The first sampling unit was the Family Doctors, with 182 doctors being selected. They, in turn, included between 12 and 20 consecutive patients who were seen at their clinics, and who met with the previously defined criteria [10]. The patients were contacted by telephone from the clinic by their own doctor, and the data was collected by personal interview between November 2007 and March 2008.

The patients included were those who were over 18 years-old (adult legal age in Spain), with a confirmed diagnosis of asthma for at least one year according to GINA criteria [11], who had visited a Health Centre in the previous 2 years, and signed the informed consent. Those individuals who, in the investigator’s opinion, were unable to read or understand the questionnaires, or had Chronic Obstructive Pulmonary Disease, were excluded [10].

Data were collected by personal interview, carried out by the Family Doctors themselves, with no specific training for this study.

The HRQoL was assessed using the EQ-5D questionnaire, where the patients themselves evaluated their state of health in severity levels by dimensions (including the 5 dimensions: mobility, personal care, daily activities, pain/discomfort, anxiety/depression) which were assessed at three levels (no problems, moderate problems, serious problems). An assessment was also made on a more general VAS scale ranging from 0 (worst state of health) to 100 (better state of health) [12].

Control of the asthma was determined using the Asthma Control Questionnaire (ACQ) [13]. Those patients who obtained an ACQ score lower than 0.75 were considered as well controlled, and those with a score ≥ 0.75 as not well controlled [10, 13].

Using a questionnaire specifically designed for the study, the characteristics of the asthma disease were collected, as well as the adherence to treatment, and the socio-demographic variables, including: age, gender, place of residence (rural/urban), and educational levels (primary school, secondary school, university).

As regards smoking, they were classified into never smokers (means never having smoked habitually, no more than an occasional cigarette), ex-smokers (have been active smokers, but have not smoked for at least 6 months), or active smokers (smoke habitually every day).

Obesity was classified based on the body mass index (BMI), establishing 3 groups, normal weight (less than 25 kg/m2), overweight (between 25 and 30 kg/m2) and obese (more than 30 kg/m2).

The incidence of stressful events in the 15 days prior to completing the questionnaire was evaluated based on self-reporting by the patients, by asking them if they had suffered a stressful event in the previous 15 days, in general, without suggesting specific examples of a stressful events, with two response options, yes or no.

Treatment adherence was determined based on 3 variables: 1) level of therapeutic adherence according to the doctor; 2) frequency of forgetting the medication according to the patient; 3) importance of adherence according to the patient [10]. This last variable was determined by asking the patients about their level of agreement (from 0 = disagree completely, to 10 = agree completely) with the following sentence “Strict adherence to the medication prescribed by my doctor should improve my asthma symptoms”; and was stratified, by research team consensus, into two categories: <8 and ≥8 [10].

The severity of the asthma (intermittent, mild persistent, moderate persistent, severe persistent) was determined in accordance with the criteria in the Global Initiative for Asthma guide (GINA) 2006, based on the condition of the patient before treatment was started [11].

The presence of allergy sensitization was reported by the patients themselves. Questions on going to an Emergency unit, to their Family Doctor or any hospital admissions during the year prior to the study were included in the questionnaire.

The basic treatment was classified into four, mutually exclusive, categories: 1) patients treated with oral corticosteroids in the previous year; 2) those treated with any combination of long-acting beta-2 agonists and inhaled corticosteroids, with any other drug but without oral corticosteroids; 3) treated with inhaled corticosteroids without continually taking long-acting beta-2 agonists, although they may take beta-2 agonists on demand; 4) only beta-2 agonists [10].

Statistical analysis

The mean, median, standard deviation, maximum and minimum values were calculated for the continuous variables, and the absolute and relative frequencies for the categorical variables.

The influence of the different variables included in the study on the 5 dimensions of the EQ-5D recoded dichotomically (without problems versus with problems) and the probability of obtaining values greater than the mean on the VAS scale were evaluated using multivariate logistic regression analysis. For the logistic regression model, all variables with a significance value of P < 0.2 in the univariate analysis were used as predictive variables in the multivariate analysis. The level of significance in the multivariate analysis was defined based on the confidence interval with an alpha error less than 0.05. The software SAS v8.2 was used. The study was approved by the Hospital Clínico San Carlos de Madrid Clinical Research Ethics Committee.

Results

A total of 2,125 patients were finally included, with 57.7% females, and a mean age of 48 years. The response rate was 95.4%. The main characteristics of the patients included are summarized in Table 1.
Table 1

Factors associated with health-related quality of life (n = 2,125)

 

% patients without problems

Gender

 

Female

883/1,227 (72.0%)

Male

726/898 (80.8 %)

Age

 

≥ 60 years

335/638 (52.5%)

40 to 59 years

551/704 (78.3%)

18 to 39 years

723/783 (92.3%)

BMI (Kg/m 2 )

 

≥ 30

243/424 (57.3%)

≥ 25 to 30

656/873 (75.1%)

< 25

709/826 (85.8%)

Educational level

 

None

74/170 (43.5%)

Primary

613/900 (68.1%)

Secondary

600/706 (85.0%)

University

319/345 (92.5%)

Occupation

 

Non active worker

648/1,029 (63.0%)

Active worker

960/1,094 (87.7%)

Living status

 

Lives alone

145/237 (61.2%)

Lives with someone

1461/1,885 (77.5%)

Place of residence

 

Rural

632/859 (73.6%)

Urban

977/1,265 (77.2%)

Family history of asthma

 

Yes

744/984 (75.6%)

No

865/1,141 (75.8%)

Asthma severity

 

Severe persistent

28/90 (31.1%)

Moderate persistent

449/706 (63.6%)

Mild persistent

655/774 (84.6%)

Intermittent

476/554 (85.9%)

Smoking habit

 

Never

1006/1,339 (75.1%)

Current or former

601/784 (76.7%)

Alcohol intake

 

≤ 22.5 grams

705/940 (75.0%)

> 22.5 grams

732/944 (77.5%)

Pets at home

 

Yes

473/626 (75.6%)

No

1,134/1,497 (75.7%)

Allergy sensitization

 

No

871/1,201 (72.5%)

Yes

738/924 (79.9%)

Stressful event last 15 days

 

Yes

207/307 (67.4%)

No

1,394/1,810 (77.0%)

Adherence to treatment (physician’s point of view):

Very poor

31/40 (77.5%)

Poor

224/313 (71.6%)

Acceptable

624/805 (77.5%)

Good

562/743 (75.6%)

Very good

168/224 (75.0%)

How often do you forget your medication?

 

>10 times every month

51/76 (67.1%)

6-10 times every month

163/223 (73.1%)

1-5 times every month

764/999 (76.5%)

Never

631/827 (76.3)

Adherence is important (score, patient’s point of view):

< 8

388/531 (73.1%)

≥ 8

1,220/1,591 (76.7%)

Asthma treatment

 

Oral corticosteroids

62/158 (39.2%)

LABA + IC

1,114/1,476 (75.5%)

Inhaled corticosteroids

180/209 (86.1%)

SABA or LABA

230/255 (90.2%)

ACQ score

 

>1.50

437/792 (55.2%)

0.75-1.50

464/561 (82.7%)

<0.75

708/772 (91.7%)

Asthma control(physician’s point of view):

 

Very poor

43/83 (51.8%)

Poor

172/322 (53.4%)

Controlled

504/721 (69.9%)

Total control

889/997 (89.2%)

Asthma control (patient’s point of view)

Very poor

11/41 (26.8%)

Poor

97/191 (50.8%)

Controlled

432/666 (64.9%)

Total control

1,060/1,217 (87.1%)

Hospital admissions

 

Yes

54/179 (30.2%)

No

1,555/1,946 (79.9%)

Number of hospital admissions

 

≥2

10/52 (19.2%)

1

44/127 (34.6%)

0

1,555/1,946 (79.9%)

Emergency visits

 

Yes

503/810 (62.1%)

No

1,106/1,315 (84.1%)

Number of emergency visits

 

≥3

84/213 (39.0%)

1-2

419/596 (70.3%)

0

1,106/1,315 (84.1%)

Family physician visits

 

No

97/112 (86.6%)

Yes

1,506/2,012 (75.1%)

Number of family physician visits

 

0

97/112 (86.6%)

< 4

675/786 (85.9%)

≥ 4

831/1,221 (68.1%)

Through the analysis of the different dimensions evaluated with the EQ-5D questionnaire, the worst results corresponded to anxiety/depression, where 32% of asthmatics were shown to have problems. On the other hand, asthma seemed to have little effect on personal care, as only 8% mentioned problems on this aspect (Table 2).
Table 2

Factors associated with health-related quality of life, according dimensions of EuroQol-5D questionnaire (n = 2,125)

A

% patients without problems

Mobility Adjusted OR (95%CI)*

Gender

Female

883/1,227 (72.0%)

1

Male

726/898 (80.8%)

1.49 (1.13,1.97)

Age

≥ 60 years

335/638 (52.5%)

1

40 to 59 years

551/704 (78.3%)

1.96 (1.41,2.73)

18 to 39 years

723/783 (92.3%)

4.13 (2.71,6.32)

BMI (Kg/m 2 )

≥ 30

243/424 (57.3%)

1

≥ 25 to 30

656/873 (75.1%)

1.64 (1.20,2.23)

< 25

709/826 (85.8%)

2.14 (1.50,3.04)

Educational level

None

74/170 (43.5%)

1

Primary

613/900 (68.1%)

1.46 (0.97,2.20)

Secondary

600/706 (85.0%)

1.77 (1.10,2.85)

University

319/345 (92.5%)

3.19 (1.73,5.88)

Occupation

Non active worker

648/1,029 (63.0%)

1

Active worker

960/1,094 (87.7%)

1.43 (1.04,1.97)

Living status

Lives alone

145/237 (61.2%)

1

Lives with someone

1,461/1,885 (77.5%)

1.60 (1.10,2.33)

ACQ score

>1.50

437/792 (55.2%)

1

0.75-1.50

464/561 (82.7%)

2.68 (1.96,3.66)

<0.75

708/772 (91.7%)

4.83 (3.37,6.92)

Hospital admissions

Yes

54/179 (30.2%)

1

No

1,555/1,946 (79.9%)

2.64 (1.71,4.07)

B

% patients without problems

Self-care Adjusted OR (95%CI)*

Age

≥ 60 years

335/638 (52.5%)

1

40 to 59 years

551/704 (78.3%)

2.25 (1.34,3.75)

18 to 39 years

723/783 (92.3%)

4.30 (1.93,9.54)

Educational level

None

74/170 (43.5%)

1

Primary

613/900 (68.1%)

3.08 (1.89,5.03)

Secondary

600/706 (85.0%)

2.71 (1.40,5.24)

University

319/345 (92.5%)

3.21 (1.20,8.54)

Occupation

Non active worker

648/1,029 (63.0%)

1

Active worker

960/1,094 (87.7%)

2.77 (1.52,5.04)

Living status

Lives alone

145/237 (61.2%)

1

Lives with someone

1,461/1,885 (77.5%)

1.70 (1.03,2.80)

Asthma severity

Severe persistent

28/90 (31.1%)

1

Moderate persistent

449/706 (63.6%)

1.81 (0.98,3.34)

Mild persistent

655/774 (84.6%)

3.32 (1.61,6.85)

Intermittent

476/554 (85.9%)

3.21 (1.38,7.46)

Stressful event last 15 days

Yes

207/307 (67.4%)

1

No

1,394/1,810 (77.0%)

1.99 (1.22,3.26)

Asthma treatment

Oral corticosteroids

62/158 (39.2%)

1

LABA + IC

1,114/1,476 (75.5%)

1.34 (0.77,2.32)

Inhaled corticosteroids

180/209 (86.1%)

4.07 (1.07,15.48)

SABA or LABA

230/255 (90.2%)

1.76 (0.58,5.33)

ACQ score

>1.50

437/792 (55.2%)

1

0.75-1.50

464/561 (82.7%)

2.49 (1.43,4.36)

<0.75

708/772 (91.7%)

2.69 (1.41,5.14)

Hospital admissions

Yes

54/179 (30.2%)

1

No

1,555/1,946 (79.9%)

2.52 (1.52,4.17)

C

% patients without problems

Usual activities Adjusted OR (95%CI)*

Age

≥ 60 years

335/638 (52.5%)

1

40 to 59 years

551/704 (78.3%)

2.27 (1.63,3.16)

18 to 39 years

723/783 (92.3%)

2.67 (1.80,3.95)

BMI (Kg/m 2 )

≥ 30

243/424 (57.3%)

1

≥ 25 to 30

656/873 (75.1%)

1.27 (0.93,1.73)

< 25

709/826 (85.8%)

1.43 (1.02,2.02)

Educational level

None

74/170 (43.5%)

1

Primary

613/900 (68.1%)

1.51 (0.99,2.31)

Secondary

600/706 (85.0%)

1.86 (1.16,2.99)

University

319/345 (92.5%)

2.62 (1.49,4.60)

Living status

Lives alone

145/237 (61.2%)

1

Lives with someone

1,461/1,885 (77.5%)

1.76 (1.23,2.53)

Asthma severity

Severe persistent

28/90 (31.1%)

1

Moderate persistent

449/706 (63.6%)

1.75 (0.95,3.24)

Mild persistent

655/774 (84.6%)

1.97 (1.04,3.74)

Intermittent

476/554 (85.9%)

1.76 (0.90,3.45)

Asthma treatment

Oral corticosteroids

62/158 (39.2%)

1

LABA + IC

1,114/1,476 (75.5%)

1.41 (0.88,2.23)

Inhaled corticosteroids

180/209 (86.1%)

2.43 (1.27,4.62)

SABA or LABA

230/255 (90.2%)

1.97 (1.05,3.71)

ACQ score

>1.50

437/792 (55.2%)

1

0.75-1.50

464/561 (82.7%)

3.74 (2.79,5.09)

<0.75

708/772 (91.7%)

7.48 (5.29,10.58)

Hospital admissions

Yes

54/179 (30.2%)

1

No

1,555/1,946 (79.9%)

1.75 (1.14,2.68)

Emergency visits

Yes

503/810 (62.1%)

1

No

1,106/1,315 (84.1%)

1.67 (1.28,2.17)

D

% patients without problems

Pain/Discomfort Adjusted OR (95%CI)*

Gender

Female

883/1,227 (72.0%)

1

Male

726/898 (80.8%)

1.55 (1.17,2.06)

Age

≥ 60 years

335/638 (52.5%)

1

40 to 59 years

551/704 (78.3%)

2.32 (1.68,3.22)

18 to 39 years

723/783 (92.3%)

5.27 (3.52,7.88)

BMI (Kg/m 2 )

≥ 30

243/424 (57.3%)

1

≥ 25 to 30

656/873 (75.1%)

1.36 (1.00,1.85)

< 25

709/826 (85.8%)

1.75 (1.25,2.47)

Educational level

None

74/170 (43.5%)

1

Primary

613/900 (68.1%)

1.59 (1.02,2.49)

Secondary

600/706 (85.0%)

1.88 (1.14,3.09)

University

319/345 (92.5%)

2.23 (1.25,3.99)

Occupation

Non active worker

648/1029 (63.0%)

1

Active worker

960/1094 (87.7%)

1.43 (1.06,1.93)

Asthma severity

Severe persistent

28/90 (31.1%)

1

Moderate persistent

449/706 (63.6%)

2.24 (1.14,4.41)

Mild persistent

655/774 (84.6%)

3.35 (1.66,6.75)

Intermittent

476/554 (85.9%)

2.65 (1.28,5.48)

Stressful event last 15 days

Yes

207/307 (67.4%)

1

No

1,394/1,810 (77.0%)

2.04 (1.46,2.83)

ACQ score

>1.50

437/792 (55.2%)

1

0.75-1.50

464/561 (82.7%)

1.80 (1.33,2.44)

<0.75

708/772 (91.7%)

2.78 (1.99,3.88)

Hospital admissions

Yes

54/179 (30.2%)

1

No

1,555/1,946 (79.9%)

2.05 (1.30,3.25)

Emergency visits

Yes

503/810 (62.1%)

1

No

1,106/1,315 (84.1%)

1.37 (1.03,1.81)

E

% patients without problems

Anxiety/Depression Adjusted OR (95%CI)*

Gender

Female

883/1,227 (72.0%)

1

Male

726/898 (80.8%)

1.84 (1.41,2.41)

Age

≥ 60 years

335/638 (52.5%)

1

40 to 59 years

551/704 (78.3%)

1.35 (0.98,1.87)

18 to 39 years

723/783 (92.3%)

2.37 (1.62,3.47)

Educational level

None

74/170 (43.5%)

1

Primary

613/900 (68.1%)

2.04 (1.33,3.12)

Secondary

600/706 (85.0%)

2.18 (1.36,3.49)

University

319/345 (92.5%)

2.55 (1.49,4.37)

Place of residence

Rural

632/859 (73.6%)

1

Urban

977/1265 (77.2%)

1.28 (1.01,1.62)

Asthma severity

Severe persistent

28/90 (31.1%)

1

Moderate persistent

449/706 (63.6%)

1.74 (0.96,3.15)

Mild persistent

655/774 (84.6%)

2.61 (1.40,4.87)

Intermittent

476/554 (85.9%)

2.27 (1.19,4.33)

Stressful event last 15 days

Yes

207/307 (67.4%)

1

No

1,394/1,810 (77.0%)

5.57 (4.08,7.59)

ACQ score

>1.50

437/792 (55.2%)

1

0.75-1.50

464/561 (82.7%)

1.36 (1.01,1.83)

<0.75

708/772 (91.7%)

1.66 (1.21,2.28)

Hospital admissions

Yes

54/179 (30.2%)

1

No

1,555/1,946 (79.9%)

2.09 (1.36,3.22)

Emergency visits

Yes

503/810 (62.1%)

1

No

1,106/1,315 (84.1%)

1.32 (1.02,1.72)

*Adjusted Odds Ratio (Adjusted by all the variables in the Table 1).

NS, Crude Odds Ratio non significant; BMI, Body mass index; SABA, Short- acting beta2 agonists; LABA, Long-acting beta2 agonists; SD, Standard Deviation; IC, Inhaled corticosteroids.

Advanced age, a lower education level, greater baseline severity of the asthma, poor control of the asthma, and the need to be admitted to hospital had a detrimental effect on at least 4 of the 5 EQ-5D dimensions (Table 2). Analyzing the quality of life according to the VAS and with the EQ-5D index, the characteristics with the most significant influence on analyzing the QoL by dimensions maintained their impact. Other factors also demonstrated an independent effect, amongst which the most significant one corresponded to patients who had some recent stressful events, or who gave little importance to adherence to treatment (Table 3).
Table 3

Factors associated with health-related quality of life: VAS scale (0 = worst health state, 100 = best health state); (n = 2034)

  

VAS score

 

N

Mean (SD)

Adjusted mean differences (CI 95 %)*

Age

   

≥ 60 years

609

62.38 (17.46)

 

40 to 59 years

675

68.93 (16.66)

1.78 (−0.38,3.94)

18 to 39 years

750

76.34 (15.33)

4.99 (2.63,7.37)

Educational level

   

None

162

58.57 (18.52)

 

Primary

865

66.12 (17.18)

2.41 (−0.63,5.44)

Secondary

667

73.48 (16.02)

4.96 (1.64,8.28)

University

336

76.87 (14.92)

6.30 (2.69,9.90)

Asthma severity

   

Severe persistent

87

46.78 (17.21)

 

Moderate persistent

672

65.45 (16.86)

9.01 (5.07,12.96)

Mild persistent

754

72.97 (15.12)

11.40 (7.28,15.52)

Intermittent

520

74.26 (16.96)

9.49 (5.22,13.76)

Smoking habit

   

Current or former

753

68.47 (17.02)

 

Never

1,279

70.43 (17.58)

2.51 (1.13,3.89)

Stressful event last 15 days

   

Yes

296

61.47 (18.61)

 

No

1,731

71.10 (16.75)

6.17 (4.31,8.03)

Adherence is important (score, patient’s point of view):

   

< 8

511

65.25 (17.78)

 

≥ 8

1,521

71.23 (16.98)

4.02 (2.54,5.50)

ACQ score

   

>1.50

762

58.94 (16.38)

 

0.75-1.50

541

72.59 (13.89)

9.48 (7.53,11.44)

<0.75

731

78.79 (14.48)

13.26 (11.22,15.29)

Score of VAS scale, and probability of obtaining values greater than the mean on the VAS. Multivariate analysis.

*Adjusted by all the variables in the Table 1.

N, number of cases; VAS, Visual Analogue Scale; CI, Confidence interval; BMI, Body mass index; SABA, Short- acting beta2 agonists; LABA, Long-acting beta2 agonists; IC, Inhaled corticosteroids.

Discussion

It appears to be a current need to assess HRQoL in asthma, although it is still not clear which is the most suitable tool for assessing it [14]. EQ-5D is a generic HRQoL questionnaire that correlates well with asthma specific questionnaires. Also, the broader approach of generic questionnaires can give them a higher potential to pick up unexpected aspects or collateral effects of the disease. These two factors make it reasonably valid for population studies with asthmatic patients [5, 1517]. Furthermore, being a generic questionnaire, it helps in making the cost comparison with other chronic illnesses [14]. The response rate obtained in our study was relatively high (95.4%), and probably associated, at least partly, with the simplicity and rapidity in completing the EQ-5D questionnaire; which also makes it easier to use in daily practice [18].

Our results appear to confirm the negative effect of asthma on HRQoL when assessed with the EQ-5D questionnaire, and this effect appears worse than that reported in the general Spanish population [19]. Only the pain/discomfort dimension and the values obtained on the VAS for the general population are similar to those of our asthmatic population, but there are significant differences in the rest of the dimensions [19].

Increasing age, lower educational level, poorer asthma control and requiring hospital admissions were significant determining factors of a poorer HRQoL in asthmatic patients in all the dimensions analyzed, as well as in the general HRQoL analyzed using the VAS.

Although in some studies with few patients [20], or with a relatively young population [21] no association was seen between age and HRQoL, the majority of authors mention a deterioration in HRQoL with increasing age [5, 8, 22]. Some factors associated with ageing could explain this result. On the one hand, there are changes in lung function, such as an increase in airway hyper-responsiveness, accelerated decline in forced expiratory volume in one second, higher prevalence of irreversible airway obstruction, increased air trapping, reduction in chest wall compliance, a decrease in static elastic recoil pressure of the lung, reduction in respiratory muscle strength, as well as changes in chest configuration which make respiratory movements difficult [23, 24]. There are also changes in the immune system, immunosenescence, which increases susceptibility to infections and malignancy rates [25]. Likewise, a deterioration in sight and hearing, in motor abilities, or even incipient cognitive impairment, can make adherence to treatment difficult [23]. Finally, comorbidity is more frequent in advanced age, as such that it may increase the symptomatology, and even make it difficult to indicate some treatments that may be suitable for asthma, but contraindicated by some of the respiratory comorbidities [23, 24].

Lower health literacy has been reported in patients with a lower education level, as well as, lower mathematical skills, more delayed diagnosis of asthma, poorer access to health care or less adherence to healthy lifestyles, which could contribute to the worsening of HRQoL observed in these patients [2629].

Hospital admissions are a major predictor of a worse HRQoL in asthma [8]; but a worse HRQoL is also associated with a higher probability of hospital admissions [30].

Good control of the disease has a significant effect on a better HRQoL, which is in agreement with other authors [5, 31]. However, to achieve good control of the disease does not imply obtaining an optimum HRQoL, as other factors, such as the presence of the disease itself, or the need for treatment and medical care, although improving control of the asthma, have an effect on the HRQoL [31].

Although there is a known relationship between asthma and psychological factors, the impact of psychological distress on the health of asthmatics and its determining factors are not well described [32]. Some authors observed a worse quality of life in asthmatics with anxiety and/or depression [3335]. On the other hand, Heaney et al., observed that the improvement in asthma control led to a better quality of life, but did not change the psychiatric symptoms. [36]. Furthermore, there is no single method to assess negative life events (NLE), understood as events that occur in the patient’s life that lead to stress, such as financial losses, work difficulties, death of a close friend or family, or other family problems [3]. In our case, this information was provided by the patients themselves. Behavioural and pathophysiological changes have been reported as determining factors in these NLE on asthma. For the former aspect, self-care could be reduced, or inadequate use of the medication [32, 37], and for the latter, an increase in airway inflammation has recently been demonstrated in asthmatic patients after stressful events [38].

Patients with more severe forms of asthma have a worse HRQoL, both in our population and in others [8, 39]. However, a recent population study in the USA did not see a relationship between severity and the HRQoL [5]. Another study in a Japanese population, observed deterioration in the HRQoL with the increasing severity of asthma in males, but not in females, establishing the possibility of different “coping styles” between the sexes [40].

Patients who remain in active employment have a better QoL, a similar finding to that of Siroux in a multicentre European study [8]. Lack of occupational activity is associated with a lower socio-economic income and greater psychological distress, which could be determining factors in the deterioration of the QoL [3, 41].

Living in an urban setting is associated with a better HRQoL. The same relationship was observed in a large study with Spanish children, suggesting the possibility that urban areas could have better access to the health system [42]. Other differences have also been identified in the management of the disease, with a lower likelihood of scheduled follow up or a greater under-diagnosis in patients in rural areas [43, 44].

The damaging effect of living alone appears to be confirmed, given that it is associated to a worse QoL. This is in agreement with other studies, where to live alone was a predictive factor of more visits to the Emergency Department, worse mental health or longer delay in the diagnosis [29, 45, 46].

In other aspects analyzed, our findings agree with those mentioned in the literature, showing more exacerbations [8, 30]; female sex [8, 47]; less adherence to treatment [48]; being someone who never smoked [5, 49]; and obesity [8, 50] are determining factors of a worse quality of life.

Our study may have some limitations. Firstly, being a cross-sectional study causality relationships cannot be defined. Secondly, the reference NLE is by self-report, as such any influence of the personality of the patients cannot be excluded. Thirdly, the selection of the participating doctors was not strictly randomized. However, given the high number of participating doctors and the distribution over the whole country, as well as the collection of data with validated tools like the EQ-5D questionnaire, the inclusion of a significant number of co-variables that could have an influence on the quality of life, and the high number of patients analyzed, these results should be reasonably valid as representative of the reality of the QoL of asthmatics in Spain and its determining factors.

Conclusions

In our study, we could identify some factors related to worst quality of life in asthma patients.

The most significant were advanced age, lower education level, greater baseline severity of the asthma, presence of stressful events, poor control of the asthma, and need to be admitted to hospital.

We believe that the identification of factors related to poor asthma control, and particularly those that could be changed by the health care system [10], could lead to an improvement in the situation of asthmatic patients. Thus, the prevention and treatment of obesity and smoking, as well as reinforcing health education, seem to be basic aspects that could be performed by the health care system.

Abbreviations

HRQoL: 

Health-related quality of life

EQ-5D: 

EuroQol-5D

VAS: 

Visual analogue scale

BMI: 

Body mass index

GINA: 

Global Initiative for Asthma guide.

Declarations

Authors’ Affiliations

(1)
Pneumology Department, Clinic University Hospital
(2)
Internal Medicine Department, Clinic University Hospital
(3)
Medical Department, AstraZeneca Farmacéutica
(4)
CIBER of Epidemiology and Public Health (CIBERESP), Preventive Medicine Department, University of Santiago de Compostela

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© Gonzalez-Barcala et al.; licensee BioMed Central Ltd. 2012

This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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