umu.sePublications
Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Lung function and prevalence trends in asthma and COPD: the Obstructive Lung Disease in Northern Sweden Thesis XVI
Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Occupational and Environmental Medicine. (OLIN)ORCID iD: 0000-0002-0553-8067
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Background

Asthma and chronic obstructive pulmonary disease (COPD) are common obstructive airway diseases with a substantial burden in terms of morbidity, mortality and costs. Smoking is the single most important risk factor for COPD, and is associated with incident asthma. It is important to know if the prevalence of asthma and COPD is increasing or decreasing in the population in order to effectively allocate health care resources. The definitions of these diseases have varied over time which makes it difficult to measure changes in prevalence. The preferred method is to estimate the prevalence with the same procedures and definitions based on cross-sectional population samples with identical age distributions in the same geographical area at different time points. Measurements of lung function (spirometry) are required to diagnose COPD, and spirometry is used to evaluate disease severity and progress of both asthma and COPD, where observed values are compared to reference values. The most commonly used reference values in Sweden are published during the mid 1980s, and there are few evaluations of how appropriate they are today based on Swedish population samples. The aim of the thesis was to estimate trends in the prevalence of asthma and COPD in relation to smoking habits, and to evaluate and estimate reference values for spirometry.

Methods

The project was based on population-based samples of adults from the Obstructive Lung Disease in Northern Sweden (OLIN) studies. Postal questionnaires were sent to large cohorts, recruited in 1992 (n=4851, 20-69 years), 1996 (n=7420, 20-74 years) and 2006 (n=6165, 20-69 years), respectively. The questionnaire included questions on respiratory symptoms and diseases, their comorbidities and several possible risk factors including smoking habits. Structured interviews and spirometry were performed in random samples of the responders to the 1992 and 2006 surveys, of which n=660 (in 1994) and n=623 (in 2009) were within identical age-spans (23-72 years). The trend in asthma prevalence was estimated by comparing the postal questionnaire surveys in 1996 and 2006, and the trend in COPD prevalence was estimated by comparing the samples participating in dynamic spirometry in 1994 and 2009, respectively. The prevalence of COPD was estimated based on two different definitions of COPD. Commonly used reference values for spirometry were evaluated based on randomly sampled healthy non-smokers defined in clinical examinations of participants in the 2006 postal questionnaire (n=501). The main focus of the evaluation was the global lung function initiative (GLI) reference values published in 2012, for which Z-scores and percent of predicted values were analysed. New sex-specific reference values for spirometry were estimated by linear regression, with age and height as predictors. These new OLIN reference values were also evaluated on a sample of healthy non-smokers identified in the population-based West Sweden Asthma Study.

Results

Although the prevalence of smoking decreased from 27.4% to 19.1%, p<0.001, between 1996 and 2006, the prevalence of physician-diagnosed asthma increased from 9.4% to 11.6%, p<0.001. The prevalence of symptoms common in asthma such as recurrent wheeze did not change significantly between the surveys or tended to decrease, while bronchitis symptoms such as cough and sputum production decreased significantly. The evaluation of the GLI reference values showed that the predicted values were significantly lower compared to the observed values in Norrbotten, which makes the percent of predicted too high. This was especially true for FVC percent predicted with a mean of 106%. In general, the deviations were more pronounced among women. New OLIN reference values valid for the Norrbotten sample were modelled and showed a high external validity when applied on the sample from western Sweden. The prevalence of moderate to severe COPD decreased substantially over the 15-year period between 1994 and 2009, regardless of definition.

Conclusions

In parallel with substantially decreased smoking habits in the population between 1996 and 2006, the prevalence of several airway symptoms decreased while the prevalence of physician-diagnosed asthma increased. These results suggest increased diagnostic activity for asthma, but may also suggest that the asthma prevalence has continued to increase. In contrast to asthma, the prevalence of COPD tended to decrease and moderate to severe COPD decreased substantially. The continuous decrease in smoking in Sweden during several decades prior to the study period is most likely contributing to these results. The evaluation of reference values showed that the GLI reference values were lower than the observed spirometric values in the population, especially for women, why the new up-to date reference values may be of importance for disease evaluation in epidemiology and in the health care as well.

Place, publisher, year, edition, pages
Umeå: Umeå University , 2016. , 83 p.
Series
Umeå University medical dissertations, ISSN 0346-6612 ; 1796
Keyword [en]
reference values, spirometry, risk factors, respiratory symptoms
National Category
Public Health, Global Health, Social Medicine and Epidemiology Respiratory Medicine and Allergy Environmental Health and Occupational Health
Identifiers
URN: urn:nbn:se:umu:diva-118026ISBN: 978-91-7601-434-9 (print)OAI: oai:DiVA.org:umu-118026DiVA: diva2:911728
Public defence
2016-04-15, Aulan, Sunderby sjukhus, Luleå, 13:00 (English)
Opponent
Supervisors
Available from: 2016-03-24 Created: 2016-03-10 Last updated: 2016-05-10Bibliographically approved
List of papers
1. Prevalence trends in respiratory symptoms and asthma in relation to smoking: two cross-sectional studies ten years apart among adults in northern Sweden
Open this publication in new window or tab >>Prevalence trends in respiratory symptoms and asthma in relation to smoking: two cross-sectional studies ten years apart among adults in northern Sweden
Show others...
2014 (English)In: The World Allergy Organization journal, ISSN 1939-4551, Vol. 7, no 1, 1- p.Article in journal (Refereed) Published
Abstract [en]

BACKGROUND: Smoking is considered to be the single most important preventable risk factor for respiratory symptoms. Estimating prevalence of respiratory symptoms is important since they most often precede a diagnosis of an obstructive airway disease, which places a major burden on the society. The aim of this study was to estimate prevalence trends of respiratory symptoms and asthma among Swedish adults, in relation to smoking habits. A further aim was to estimate the proportion of respiratory symptom and asthma prevalence attributable to smoking.

METHODS: Data from two large-scale cross-sectional surveys among adults performed in northern Sweden in 1996 and 2006 were analysed. Identical methods and the same questionnaire were used in both surveys. The association between smoking, respiratory symptoms and asthma was analysed with multiple logistic regression analyses. Changes in prevalence of respiratory symptoms and asthma from 1996 to 2006 were expressed as odds ratios. Additionally, the population attributable risks of smoking were estimated.

RESULTS: The prevalence of most respiratory symptoms decreased significantly from 1996 to 2006. Longstanding cough decreased from 12.4 to 10.1%, sputum production from 19.0 to 15.0%, chronic productive cough from 7.3 to 6.2%, and recurrent wheeze from 13.4 to 12.0%. Any wheeze and asthmatic wheeze remained unchanged. This parallels to a decrease in smoking from 27.4 to 19.1%. In contrast, physician-diagnosed asthma increased from 9.4 to 11.6%. The patterns were similar after correction for confounders. All respiratory symptoms were highly associated with smoking, and the proportion of respiratory symptoms in the population attributed to smoking (PAR) ranged from 9.8 to 25.5%. In 2006, PAR of smoking was highest for recurrent wheeze (20.6%).

CONCLUSIONS: In conclusion, we found that respiratory symptoms, in particular symptoms common in bronchitis, decreased among adults in northern Sweden, parallel to a decrease in smoking from 1996 to 2006. In contrast, the prevalence of physician-diagnosed asthma increased during the same time-period. Up to one fourth of the respiratory symptom prevalence in the population was attributable to smoking.

Place, publisher, year, edition, pages
BioMed Central, 2014
Keyword
respiratory symptoms, asthma, prevalence, smoking, attributable risk, trends
National Category
Public Health, Global Health, Social Medicine and Epidemiology Respiratory Medicine and Allergy
Identifiers
urn:nbn:se:umu:diva-85536 (URN)10.1186/1939-4551-7-1 (DOI)24383710 (PubMedID)
Available from: 2014-02-06 Created: 2014-02-06 Last updated: 2017-05-09Bibliographically approved
2. Decreased prevalence of moderate to severe COPD over 15 years in northern Sweden
Open this publication in new window or tab >>Decreased prevalence of moderate to severe COPD over 15 years in northern Sweden
Show others...
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Background: The burden of COPD in terms of mortality, morbidity, costs and prevalence has increased worldwide. Recent results on prevalence in Western Europe are conflicting. In Sweden smoking prevalence has steadily decreased over the past 30 years. 

Aim: The aim was to study changes in prevalence and risk factor patterns of COPD in the same area and within the same age-span 15 years apart.

Material and methods: Two population-based cross-sectional samples in ages 23-72 years participating at examinations in 1994 and 2009, respectively, were compared in terms of COPD prevalence, severity and risk factor patterns. Two different definitions of COPD were used; FEV1/FVC<LLN and FEV1/FVC<0.7. The severity of COPD was assessed by FEV1, both as % of predicted and in relation to the LLN.

Results: The prevalence of COPD decreased significantly from 9.5% to 6.3% (p=0.030) according to the FEV1/FVC<LLN criterion, while the decrease based on the FEV1/FVC<0.7 criterion from 10.5% to 8.5% was non-significant. The prevalence of moderate to severe COPD decreased substantially and significantly, and the risk factor pattern was altered in 2009 when, beside age and smoking, also socio-economic status based on occupation was significantly associated with COPD. 

Conclusions: Changes in both prevalence and risk factor patterns of COPD were observed between surveys. Following a continuing decrease in smoking habits over several decades, a decrease in the prevalence of moderate to severe COPD was observed from 1994 to 2009 in northern Sweden.

Keyword
COPD, Prevalence, Risk factors, Epidemiology, GOLD, Lower Limit of Normal
National Category
Public Health, Global Health, Social Medicine and Epidemiology Environmental Health and Occupational Health
Research subject
hälso- och sjukvårdsforskning
Identifiers
urn:nbn:se:umu:diva-118023 (URN)
Available from: 2016-03-10 Created: 2016-03-10 Last updated: 2016-03-23Bibliographically approved
3. Evaluation of the global lung function initiative 2012 reference values for spirometry in a Swedish population sample
Open this publication in new window or tab >>Evaluation of the global lung function initiative 2012 reference values for spirometry in a Swedish population sample
Show others...
2015 (English)In: BMC Pulmonary Medicine, ISSN 1471-2466, E-ISSN 1471-2466, Vol. 15, 26Article in journal (Refereed) Published
Abstract [en]

Background: The Global Lung Function Initiative 2012 (GLI) reference values are currently endorsed by several respiratory societies but evaluations of applicability for adults resident in European countries are lacking. The aim of this study was to evaluate if the GLI reference values are appropriate for an adult Caucasian Swedish population.

Methods: During 2008-2013, clinical examinations including spirometry were performed on general population samples in northern Sweden, in which 501 healthy Caucasian non-smokers were identified. Predicted GLI reference values and Z-scores were calculated for each healthy non-smoking subject and the distributions and mean values for FEV1, FVC and the FEV1/FVC ratio were examined. The prevalence of airway obstruction among these healthy non-smokers was calculated based on the Lower Limit of normal (LLN) criterion (lower fifth percentile) for the FEV1/FVC ratio. Thus, by definition, a prevalence of 5% was expected.

Results: The Z-scores for FEV1, FVC and FEV1/FVC were reasonably, although not perfectly, normally distributed, but not centred on zero. Both predicted FEV1 and, in particular, FVC were lower compared to the observed values in the sample. The deviations were greater among women compared to men. The prevalence of airway obstruction based on the LLN criterion for the FEV1/FVC ratio was 9.4% among women and 2.7% among men.

Conclusions: The use of the GLI reference values may produce biased prevalence estimates of airway obstruction in Sweden, especially among women. These results demonstrate the importance of validating the GLI reference values in different countries.

Keyword
Lung function, Spirometry, Reference values, Z-score, Lower Limit of Normal
National Category
Respiratory Medicine and Allergy
Identifiers
urn:nbn:se:umu:diva-103744 (URN)10.1186/s12890-015-0022-2 (DOI)000353765400002 ()25887050 (PubMedID)
Available from: 2015-06-01 Created: 2015-05-28 Last updated: 2017-12-04Bibliographically approved
4. Reference values for spirometry - report from the Obstructive Lung Disease in Northern Sweden studies
Open this publication in new window or tab >>Reference values for spirometry - report from the Obstructive Lung Disease in Northern Sweden studies
Show others...
2015 (English)In: European Clinical Respiratory Journal, ISSN 2001-8525, Vol. 2, 26375Article in journal (Refereed) Published
Abstract [en]

Background: Abnormal lung function is commonly identified by comparing observed spirometric values to corresponding reference values. It is recommended that such reference values for spirometry are evaluated and updated frequently. The aim of this study was to estimate new reference values for Swedish adults by fitting a multivariable regression model to a healthy non-smoking general population sample from northern Sweden. Further aims were to evaluate the external validity of the obtained reference values on a contemporary sample from south-western Sweden, and to compare them to the Global Lung Function Initiative (GLI) reference values.

Method: Sex-specific multivariable linear regression models were fitted to the spirometric data of n=501 healthy non-smoking adults aged 22–91 years, with age and height as predictors. The models were extended to allow the scatter around the outcome variable to depend on age, and age-dependent spline functions were incorporated into the models to provide a smooth fit over the entire age range. Mean values and lower limits of normal, defined as the lower 5th percentiles, were derived.

Result: This modelling approach resulted in unbiased estimates of the spirometric outcomes, and the obtained estimates were appropriate not only for the northern Sweden sample but also for the south-western Sweden sample. On average, the GLI reference values for forced expiratory volume in one second (FEV1) and, in particular, forced expiratory vital capacity (FVC) were lower than both the observed values and the new reference values, but higher for the FEV1/FVC ratio.

Conclusion: The evaluation based on the sample of healthy non-smokers from northern Sweden show that the Obstructive Lung Disease in Northern Sweden reference values are valid. Furthermore, the evaluation based on the south-western Sweden sample indicates a high external validity. The comparison with GLI brought further evidence to the consensus that, when available, appropriate local population-specific reference values may be preferred.

Keyword
reference equations, reference sample, Z-scores, percentiles, linear regression, spline functions
National Category
Environmental Health and Occupational Health
Identifiers
urn:nbn:se:umu:diva-107514 (URN)10.3402/ecrj.v2.26375 (DOI)
Available from: 2015-08-24 Created: 2015-08-24 Last updated: 2017-05-09Bibliographically approved

Open Access in DiVA

fulltext(1480 kB)274 downloads
File information
File name FULLTEXT01.pdfFile size 1480 kBChecksum SHA-512
ae2fbe8a38d0226ee4ba6e993bf69df8c6371fc1728b1b60803cd84eafd255051a77f48875523d8429472ffb09aeabbb3874ee90f320009ceb07ab9b2e362fd6
Type fulltextMimetype application/pdf
spikblad(99 kB)19 downloads
File information
File name SPIKBLAD01.pdfFile size 99 kBChecksum SHA-512
42de06182a47fa80fa98e8b5e2fecbcc5323c1aa955d321afbc7bd4738af6af7ca711a87509200ead82dae4f31fd9e98dd9e19a9d18dc7f65c541d514d7f61cc
Type spikbladMimetype application/pdf
bilaga(1447 kB)50 downloads
File information
File name ATTACHMENT01.pdfFile size 1447 kBChecksum SHA-512
3b4594dd869f822000d7d236258ece5b37df6c66a30bc44e62aa06dbf21e7f052e74c9e60cab656f2341a774e719fdf217b314a3638faec9056a3bc5b159986e
Type attachmentMimetype application/pdf

Authority records BETA

Backman, Helena

Search in DiVA

By author/editor
Backman, Helena
By organisation
Occupational and Environmental Medicine
Public Health, Global Health, Social Medicine and EpidemiologyRespiratory Medicine and AllergyEnvironmental Health and Occupational Health

Search outside of DiVA

GoogleGoogle Scholar
Total: 274 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

isbn
urn-nbn

Altmetric score

isbn
urn-nbn
Total: 1250 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf