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Keywords:

  • asthma;
  • epidemiology;
  • prevention;
  • social determinants

Abstract

  1. Top of page
  2. Abstract
  3. Methods
  4. Results
  5. Discussion
  6. Conflict of interest
  7. Acknowledgments
  8. References

Social determinants of asthma in adults and the very old have received little attention. Hence, it was aimed to examine social determinants of asthma in adults and the very old in a national population-based setting. Data were analyzed in the UK Longitudinal Household Survey, 2009–2010. Information on demographics, living and work conditions, self-reported ever asthma and age of onset was obtained by household interview. Regional difference was also examined. Analysis involved t-test and logistic regression modeling. Of 50 994 people included in the cohort, 6269 (12.3%) had ever asthma. In 2977 people, it occurred in the adulthood (16+ years) and only 91 people had their first asthma (incident asthma) at the age when they were interviewed. Education was borderline associated with asthma in the very old. In the young and middle-aged adults, however, birth place had a significant impact. Additionally, there was no regional difference in asthma prevalence across the entire UK.

Social determinants of asthma in adults have received little attention, and measures of them were not addressed comprehensively, in particular in the very old. Hence, it was aimed to examine social determinants of asthma in adults and the very old in a national population-based setting.

Methods

  1. Top of page
  2. Abstract
  3. Methods
  4. Results
  5. Discussion
  6. Conflict of interest
  7. Acknowledgments
  8. References

Study cohort

Data were extracted and analyzed in the UK Longitudinal Household Survey (Understanding Society, access available via: http://www.understandingsociety.org.uk/) Wave 1, 2009–2010, which is a national population-based study among people above 16 years of age residing in England, Scotland, Wales, and Northern Ireland. Study design and sampling method were described and published in detail in the working paper series and can be found online [1]. Information on demographics, living and work conditions, and self-reported asthma (Has as doctor or health professional ever told you that you have any of the condition listed? What age were you when you were first told you had asthma?) was obtained by household interview.

Statistical analysis

Study variables which aimed to describe potential social determinants of asthma in adults in the UK included age, sex, birth place, age gap with parents (proxy of maternal age), education, marital status, salary (proxy of occupation), and willingness to stay in the current neighborhood (proxy of perception on neighborhood satisfaction). Likert scale was used (very agree and agree into ‘agree’; ‘neither agree nor disagree, disagree, and very disagree into ‘disagree’). In the subsequent analysis, regional difference in adult asthma was examined.

Analyses involved chi-squared test, t-test, and logistic regression modeling. Adjustments were also made to control for covariates mentioned previously and age of onset (binary: 0 = ex-asthma, 1 = new onset asthma). Effects were estimated by using odds ratios (OR) and 95% confidence intervals (CI), with P < 0.05 considered statistically significant. Statistical software STATA version 12.0 (STATA, College Station, TX, USA) was used to perform all the analyses. As it is secondary data analysis in the present study, no further ethics approval is required.

Results

  1. Top of page
  2. Abstract
  3. Methods
  4. Results
  5. Discussion
  6. Conflict of interest
  7. Acknowledgments
  8. References

There were 6269 people who ever had asthma in the study cohort, which was about 12.3% of the total study population (n = 50 994). Among those who ever had asthma, 4651 (72.8%) people still had asthma at the time of household interview and 2977 (47.5%) asthma diagnoses occurred in the adulthood (16+ years). Only 91 people had their first asthma (incident asthma) at the age when they were interviewed. Table 1 presents characteristics of participants with or without prevalent asthma.

Table 1. Characteristics of people with or without ever asthma in adults aged 16 and above
 Asthma (n = 6269, 13.2%)Nonasthma (N = 41 336, 86.8%)P value
Sex
 Male2618 (41.8%)18 357 (44.4%)0.132
 Female3651 (58.2%)22 979 (55.6%)
Age (mean ± SD)43.3 ± 18.346.3 ± 18.1 
 16–392939 (46.9%)16 231 (39.3%)<0.001
 40–591960 (31.3%)14 328 (34.7%)
 60–791172 (18.7%)9201 (22.3%)
 ≥80198 (3.2%)1576 (3.8%)
Birth place
 Born in England4569 (72.9%)26 682 (64.5%)<0.001
 Born in Scotland462 (7.4%)2944 (7.1%)
 Born in Wales329 (5.2%)1716 (4.2%)
 Born in Northern Ireland206 (3.3%)1718 (4.2%)
 Not born in the UK703 (11.2%)8269 (20.0%)
Education
 ≥high school2429 (38.7%)24 845 (60.1%)0.113
 <high school3835 (61.2%)16 446 (39.9%)
Marital status
 Never married2370 (37%)12 552 (30.4%)<0.001
 Married2710 (43.2%)21 396 (51.8%)
 Not living together1185 (18.9%)7351 (17.8%)
Salary
 <£20 0002291 (36.5%)14 504 (35.1%)0.085
 £20 000–49 999247 (3.9%)1863 (4.5%)
 £50 000–99 99952 (0.8%)362 (0.9%)
 ≥£100 0008 (0.1%)64 (0.2%)
Mother's age
 16–39314 (5.0%)2862 (6.9%)<0.001
 40–591549 (24.7%)10 505 (25.4%)
 60–791299 (20.7%)6801 (16.5%)
 ≥8040 (0.6%)115 (0.3%)
Father's age
 16–39239 (3.8%)1688 (4.1%)<0.001
 40–591402 (22.4%)9044 (21.9%)
 60–791096 (17.5%)5276 (12.8%)
 ≥8026 (0.4%)86 (0.2%)
Age gap with mother's
 10–19276 (4.4%)1636 (4.0%)0.415
 20–292126 (33.9%)13 417 (32.5%)
 ≥30800 (13.2%)5230 (12.7%)
Age gap with father's
 10–1976 (1.2%)416 (1.0%)0.290
 20–291556 (24.8%)8837 (21.4%)
 ≥301131 (18.0%)6841 (16.5%)
Neighborhood satisfaction
 Strongly agree1156 (18.4%)7525 (18.2%)<0.001
 Agree2146 (34.2%)15 050 (36.4%)
 Neither agree or disagree1034 (16.5%)6342 (15.3%)
 Disagree603 (9.6%)3224 (7.8%)
 Strongly disagree375 (6.0%)1690 (4.1%)
Work location
 At home50 (0.8%)412 (1.0%)0.332
 At the employer's premises2158 (34.4%)13 796 (33.4%)
 Driving or traveling222 (3.5%)1437 (3.5%)
 At more than one location192 (3.1%)1190 (2.9%)
 Other9 (0.1%)89 (0.2%)

Table 2 shows associated social factors for prevalent adult asthma across age groups. In the very old (age >80 year), less education was borderline associated with asthma (OR 1.36, 95% CI 1.00–3.45, P = 0.05). In the young (aged 16–39 year) and middle-aged adults (aged 40–79 year), however, birth place seemed to play a role in the prevalence (not born in the UK: OR 0.34, 95% CI 0.28–0.42, P < 0.001 and OR 0.72, 95% CI 0.57–0.90, P = 0.01, respectively). Moreover, although some regional difference in adult-prevalent asthma across age groups was observed, the significance all disappeared after full adjustments (data not shown).

Table 2. Social factors associated with prevalent asthma across age groups
 Asthma (n = 198, 11.2%)Nonasthma (N = 1576, 88.8%)P valueCrude ORAdjusted ORP valuea
a) In the elderly aged 80 and above
Sex
 Male71 (9.8%)653 (90.2%)0.131.001.000.24
 Female127 (12.1%)923 (87.9%)1.27 (0.93–1.72)1.28 (0.85–1.92)
Birth place
 Born in England148 (11.3%)1163 (88.7%)0.501.001.00 
 Born in Scotland14 (10.4%)121 (89.6%)0.91 (0.51–1.62)0.75 (0.36–1.54)0.43
 Born in Wales16 (15.2%)89 (84.8%)1.41 (0.81–2.47)0.81 (0.36–1.81)0.60
 Born in Northern Ireland5 (6.9%)67 (93.1%)0.59 (0.23–1.48)0.62 (0.22–1.77)0.38
 Not born in the UK15 (9.9%)136 (90.1%)0.87 (0.50–0.52)0.50 (0.18–1.41)0.19
Education
 ≥high school18 (7.1%)237 (92.9%)0.021.001.00 0.05
 <high school180 (11.9%)1336 (88.1%) 1.77 (1.07–2.94) 1.86 (1.00–3.45)  
Marital status
 Single/in civil partnership11 (10.7%)92 (89.3%)0.181.001.00 
 Married/registeredb53 (8.9%)543 (91.1%)0.82 (0.41–1.62)0.86 (0.36–2.05)0.73
 Separated but married2 (15.4%)11 (84.6%)1.52 (0.30–7.77)n/an/a
 Divorced/Widowed131 (12.4%)930 (87.7%)1.18 (0.61–2.26)1.02 (0.45–2.33)0.96
Neighborhood satisfaction
 Agree123 (11.3%)965 (88.7%)0.841.001.00 
 Neither agree or disagree7 (9.1%)70 (90.9%)0.78 (0.35–1.74)0.80 (0.36–1.79)0.59
 Disagree5 (11.4%)39 (88.6%)1.01 (0.39–2.60)0.99 (0.38–2.59)0.99
 Asthma (n = 3132, 11.8%)Nonasthma (N = 23 529, 88.2%)P valueCrude ORAdjusted ORP valuea
b) In middle-aged adults between 40 and 79
Sex
 Male1248 (10.5%)10 684 (89.5%)<0.0011.001.000.34
 Female1884 (12.8%)12 845 (87.2%)1.26 (1.16–1.35)0.93 (0.81–1.07)
Birth place
 Born in England2199 (12.3%)15 707 (87.7%)<0.0011.001.00 
 Born in Scotland252 (11.3%)1973 (88.7%)0.91 (0.79–1.05)0.94 (0.74–1.19)0.59
 Born in Wales167 (13.5%)1066 (86.5%)1.12 (0.94–1.33)1.03 (0.75–2.43)0.84
 Born in Northern Ireland117 (10.2%)1032 (89.8%)0.81 (0.67–0.99) 0.60 (0.39–0.92) 0.02
 Not born in the UK397 (9.6%)3746 (90.4%) 0.76 (0.68–0.85) 0.72 (0.57–0.90) 0.01
Education
 ≥high school1067 (11.4%)8273 (88.6%)0.2311.001.000.07
 <high school2063 (11.9%)15 245 (88.1%)1.05 (0.97–1.14)0.88 (0.76–1.01)
Marital status
 Single/in civil partnership409 (12.8%)2797 (87.2%)<0.0011.001.00 
 Married/registeredb1825 (10.8%)15 145 (89.3%) 0.82 (0.74–0.92) 0.85 (0.69–1.04)0.11
 Separated but married118 (13.4%)763 (86.6%)1.06 (0.85–1.32)1.35 (0.95–1.92)0.09
 Divorced/Widowed780 (13.9%)4811 (86.1%)1.11 (0.98–1.26)1.02 (0.80–1.30)0.86
Salary
 <20 00094 (11.3%)7333 (88.7%)0.3651.001.00 
 20 000–49 999115 (9.8%)1065 (90.2%)0.85 (0.69–1.04)0.80 (0.64–1.00)0.06
 50 000–99 99929 (9.6%)272 (90.4%)0.84 (0.57–1.23)0.75 (0.49–1.14)0.18
 ≥100 0006 (11.5%)46 (88.5%)1.02 (0.44–2.40)1.03 (0.40–2.63)0.96
Age gap with mother's25.9 ± 5.126.2 ± 5.20.031.00 (1.00–1.00)1.00 (1.00–1.00)0.91
Age gap with father's28.0 ± 5.228.3 ± 5.40.14 1.001 (1.0003–1.002) 1.00 (1.00–1.00)0.18
Neighborhood satisfaction
Agree1946 (11.5%)14 935 (88.5%)0.011.001.00 
Neither agree or disagree404 (12.1%)2943 (87.9%)1.05 (0.94–1.18)1.07 (0.89–1.28)0.46
Disagree269 (13.9%)1668 (86.1%)1.24 (1.08–1.42)1.05 (0.84–1.32)0.65
 Asthma (n = 2939, 15.3%)Nonasthma (N = 16 231, 84.7%)P valueCrude ORAdjusted ORP valuea
  1. a

    P values denote those of adjusted ORs.

  2. b

    Including same sex couples.

  3. c

    All bold values are significant.

c) In young adults aged between 16 and 39
Sex
 Male1299 (15.6%)7020 (84.4%)0.341.001.000.2
 Female1640 (15.1%)9211 (84.9%)0.96 (0.89–1.04)0.93 (0.82–1.04)
Birth place
 Born in England2222 (18.5%)9812 (81.5%)<0.0011.001.00 
 Born in Scotland196 (18.7%)850 (81.3%)1.02 (0.87–1.20)0.92 (0.73–1.16)0.48
 Born in Wales146 (20.7%)561 (79.3%)1.15 (0.95–1.39)1.22 (0.95–1.58)0.12
 Born in Northern Ireland84 (12.0%)619 (88.0%) 0.60 (0.47–0.76) 0.53 (0.37–0.74) <0.001
 Not born in the UK291 (6.2%)4387 (93.8%) 0.29 (0.26–0.33) 0.34 (0.28–0.42) <0.001
Education
 ≥high school1345 (15.5%)7953 (84.5%)0.0011.001.000.78
 <high school1593 (16.2%)8270 (83.8%) 1.14 (1.05–1.23) 0.98 (0.87–1.11)
Marital status
 Single/in civil partnership1950 (16.8%)9669 (83.2%)<0.0011.001.00 
 Married/registeredb833 (12.7%)5719 (87.3%)0.72 (0.66–0.79)0.79 (0.69–0.90)0.001
 Separated but married60 (15.3%)332 (84.7%)0.90 (0.68–1.18)0.97 (0.60–1.55)0.89
 Divorced/Widowed94 (15.6%)495 (84.0%)0.94 (0.75–1.18)1.04 (0.75–1.43)0.83
Salary
 <20 0001358 (15.9%)7169 (84.1%)0.2521.001.00 
 20 000–49 999132 (14.2%)799 (85.8%)0.87 (0.72–1.06)0.89 (0.72–1.09)0.27
 50 000–99 99923 (20.2%)91 (79.8%)1.33 (0.84–2.16)1.33 (0.81–2.18)0.25
 ≥100 0002 (10.0%)18 (90.0%)0.59 (0.14–2.53)0.63 (0.14–2.75)0.54
Age gap with mother's26.4 ± 5.426.5 ± 5.60.581.00 (1.00–1.00)1.00 (1.00–1.00)0.47
Age gap with father's26.2 ± 5.326.4 ± 5.40.141.002 (1.0003–1.003)1.00 (1.00–1.00)0.15
Neighborhood satisfaction
 Agree1235 (15.6%)6691 (84.4%)0.0021.001.000.96
 Neither agree or disagree623 (15.8%)3333 (84.3%)1.06 (0.97–1.38)1.00 (0.86–1.15)
 Disagree704 (18.0%)3208 (82.0%) 1.22 (1.09–1.35)1.12 (0.97–2.30)0.12

Discussion

  1. Top of page
  2. Abstract
  3. Methods
  4. Results
  5. Discussion
  6. Conflict of interest
  7. Acknowledgments
  8. References

Main findings

In the present study, it was observed that birth place and education were significant social contributors to risk of adult-prevalent asthma throughout the UK, which is similar to previous studies showing low socioeconomic status (SES) is associated with higher risk of (adult) asthma [2-11].

Previous observations

In the United States, there were ethnic variations observed in people with asthma and differences in SES partially explained ethnic disparities in adult asthma [7, 8]. In the UK, ethnic disparities were explained by birth place as people who are not born in the UK tend to be immigrants from populations other than white people [12]. This may be related to their early living environment and/or lower SES in the UK. In this context, birth place was used to replace ethnicity in the present study. Salary was not able to be included for the analysis in the very old due to lack of information. Interestingly, being married was found to have slightly lowered risk of adult asthma for the middle aged. It is not clear whether it was due to a better marriage life lessening the risk effect of having asthma or more healthier people getting married. However, the effect disappeared after the full adjustments.

Moreover, maternal age seemed to play a role in the middle aged as well. Different from the previous observation showing higher risk from young mothers [13], in the current study, it was observed that the older the father's age, the higher risk it may pose on adult asthma. However, the complex biological pathway from maternal age to asthma is still unclear, and future research is encouraged to confirm the relationship, if at all. On the other hand, neighborhood context (area-level SES) was once hypothesized to be important for adult asthma as well. Similar to previous studies, both in the UK and the US, in the current study it was also observed that people with better perception on their neighborhoods had a lower risk of adult asthma, although the effect was not significant after full adjustments [9-11].

Strengths and limitations

This study has several strengths. First, it is in a national population-based setting with a representative sampling method in the very recent years. Moreover, the very old people were included for examination which gave an opportunity to explore social predictors of asthma specifically for them. However, a few limitations still cannot be ignored. The present study did not include smoking variable, which to some extent could bias the effects from those social factors mentioned previously. Furthermore, data for new onset adult asthma as outcome were not enough (n = 91) for statistical multiple comparisons testing and can only be adjusted as a covariate for the prevalent asthma as the outcome. The interpretation of results needs to be carefully put in any context. Future research overcoming these limitations is strongly recommended.

In conclusion, birth place and education are social factors that are associated with risk of adult-prevalent asthma in the UK, but no geographic variance was found. Consistent with previous studies, low SES still plays a role in adult asthma, and public health intervention programs are suggested continuing focusing on this part.

Acknowledgments

  1. Top of page
  2. Abstract
  3. Methods
  4. Results
  5. Discussion
  6. Conflict of interest
  7. Acknowledgments
  8. References

European Centre for Environment and Human Health is supported by European Regional Development Fund and European Social Fund Convergence Programme.

References

  1. Top of page
  2. Abstract
  3. Methods
  4. Results
  5. Discussion
  6. Conflict of interest
  7. Acknowledgments
  8. References