Exposure to secondhand smoke and cognitive impairment in non-smokers: national cross sectional study with cotinine measurement.
OBJECTIVE
To examine the association between a biomarker of exposure to secondhand smoke (salivary cotinine concentration) and cognitive impairment.


METHODS
Cross sectional analysis of a national population based study.


METHODS
Stratified random sample of households throughout England.


METHODS
4809 non-smoking adults aged 50 years or more from the 1998, 1999, and 2001 waves of the Health Survey for England who also participated in the 2002 wave of the English Longitudinal Study of Ageing and provided saliva samples for cotinine assay and a detailed smoking history.


METHODS
Cognitive impairment as defined by the lowest 10% of scores on a battery of neuropsychological tests.


RESULTS
Participants who did not smoke, use nicotine products, or have salivary cotinine concentrations of 14.1 ng/ml or more were divided into four equal size groups on the basis of cotinine concentrations. Compared with the lowest fourth of cotinine concentration (0.0-0.1 ng/ml) the odds ratios (95% confidence intervals) for cognitive impairment in the second (0.2-0.3 ng/ml), third (0.4-0.7 ng/ml), and highest fourths (0.8-13.5 ng/ml) were 1.08 (0.78 to 1.48), 1.13 (0.81 to 1.56), and 1.44 (1.07 to 1.94; P for trend 0.02), after adjustment for a wide range of established risk factors for cognitive impairment. A similar pattern of associations was observed for never smokers and former smokers.


CONCLUSIONS
Exposure to secondhand smoke may be associated with increased odds of cognitive impairment. Prospective nationally representative studies relating biomarkers of exposure to cognitive decline and risk of dementia are needed.
Llewellyn
David J
DJ
Department of Public Health and Primary Care, University of Cambridge, Cambridge CB2 2SR. dl355@medschl.cam.ac.uk
Lang
Iain A
IA
Langa
Kenneth M
KM
Naughton
Felix
F
Matthews
Fiona E
FE
D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers / Q000032:analysis; D003072:Cognition Disorders / Q000209:etiology*; D003367:Cotinine / Q000032:analysis*; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D012044:Regression Analysis; D012463:Saliva / Q000737:chemistry; D014028:Tobacco Smoke Pollution / Q000009:adverse effects*
D015415:Biomarkers; D014028:Tobacco Smoke Pollution; D003367:Cotinine