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BMJ Open. 2014 Apr 23;4(4):e004958. doi: 10.1136/bmjopen-2014-004958.

Smoker, ex-smoker or non-smoker? The validity of routinely recorded smoking status in UK primary care: a cross-sectional study.

Author information

1
Department of Primary Care and Population Health, University College London, London, UK.

Abstract

OBJECTIVE:

To investigate how smoking status is recorded in UK primary care; to evaluate whether appropriate multiple imputation (MI) of smoking status yields results consistent with health surveys.

SETTING:

UK primary care and a population survey conducted in the community.

PARTICIPANTS:

We identified 354 204 patients aged 16 or over in The Health Improvement Network (THIN) primary care database registered with their general practice 2008-2009 and 15 102 individuals aged 16 or over in the Health Survey for England (HSE).

OUTCOME MEASURES:

Age-standardised and age-specific proportions of smokers, ex-smokers and non-smokers in THIN and the HSE before and after MI. Using information on time since quitting in the HSE, we estimated when ex-smokers are typically recorded as non-smokers in primary care records.

RESULTS:

In THIN, smoking status was recorded for 84% of patients within 1 year of registration. Of these, 28% were smokers (21% in the HSE). After MI of missing smoking data, the proportion of smokers was 25% (missing at random) and 20% (missing not at random). With increasing age, more were identified as ex-smokers in the HSE than THIN. It appears that those who quit before age 30 were less likely to be recorded as an ex-smoker in primary care than people who quit later.

CONCLUSIONS:

Smoking status was relatively well recorded in primary care. Misclassification of ex-smokers as non-smokers is likely to occur in those quitting smoking at an early age and/or a long time ago. Those with no smoking status information are more likely to be ex-smokers or non-smokers than smokers.

KEYWORDS:

EPIDEMIOLOGY; PRIMARY CARE; STATISTICS & RESEARCH METHODS

PMID:
24760355
PMCID:
PMC4010810
DOI:
10.1136/bmjopen-2014-004958
[Indexed for MEDLINE]
Free PMC Article
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