Sodium intake and bronchial hyperresponsiveness in adults.
BACKGROUND
Several investigations suggested a relationship between sodium intake and asthma and bronchial hyperresponsiveness (BHR), respectively. However, clinical and epidemiological studies did not show consistent finding.


OBJECTIVE
We analysed the association between dietary sodium intake and BHR to methacholine among 613 adults aged 20-65 years as one of the two German centres of the European Community Respiratory Health Survey (ECRHS).


METHODS
Dietary sodium intake was estimated from a 3-day weighed record of food intake. We applied multiple logistic regression models contrasting the three higher quartiles of sodium intake versus the lowest to assess the risk of BHR and mild BHR estimated by PD20 and PD10, respectively, controlling for potential confounders and stratified for sex. In addition, we analysed PD20 (dose of methacholine causing a fall of 20% in forced expiratory volume in 1s) as continuous variable expressed as transformed dose-response slope (tDRS) in the linear model.


RESULTS
Women were as expected more likely to be bronchial hyperresponsive (PD20: 26.1%; PD10: 52.2%) than men (PD20:15.8%; PD10: 34.8%) and had a lower mean daily sodium intake (2.36 g) compared with men (3.15 g). Logistic regression did not show any significant relationship between sodium intake and BHR in terms of PD20 after adjustment for age group, education, smoking status, body mass index and height in men or women. However, mild BHR assessed as PD10 was statistically significant positively related to the third (OR: 2.35; CI: 1.11-5.00) and highest quartile of sodium intake (OR: 2.28; CI: 1.06-4.88) in women, but not in men for third quartile (OR: 1.29; CI: 0.68-2.44) and for fourth quartile (OR: 1.07; CI: 0.56-2.07), respectively.


CONCLUSIONS
Sodium intake by several food items does not alter BHR assessed as PD20 to methacholine but may increase mild BHR assessed as PD10. We conclude that, in addition, PD10 has to be considered when the effect of sodium intake on BHR is studied.
Sausenthaler
Stefanie
S
GSF-National Research Centre for Environment and Health, Institute of Epidemiology, Neuherberg, Germany.
Kompauer
Iris
I
Brasche
Sabine
S
Linseisen
Jakob
J
Heinrich
Joachim
J
D000328:Adult; D000368:Aged; D001980:Bronchi / Q000187:drug effects; D016535:Bronchial Hyperreactivity / Q000139:chemically induced* / Q000503:physiopathology; D016085:Bronchoconstrictor Agents; D005260:Female; D005541:Forced Expiratory Volume / Q000187:drug effects; D006801:Humans; D008297:Male; D016210:Methacholine Chloride; D008875:Middle Aged; D012044:Regression Analysis; D017673:Sodium Chloride, Dietary / Q000008:administration & dosage*; D014797:Vital Capacity / Q000187:drug effects
D016085:Bronchoconstrictor Agents; D017673:Sodium Chloride, Dietary; D016210:Methacholine Chloride