English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

correspondence: Harri Hemila Department of Public Health, POB 41, University of Helsinki, Helsinki, Fin-00014, Finland Tel +358 9 191 27573 Fax +358 9 191 27570 email harri.hemila@helsinki.fi Background: Analyses in nutritional epidemiology usually assume that there is a uniform effect of a nutrient. The purpose of this study was to test whether the effect of β-carotene on common cold incidence is uniform over the population. Methods: The Alpha-Tocopherol Beta-Carotene Study, which recruited male smokers aged 50–69 years, was conducted in Finland in 1985–1993. The active follow-up lasted for 4.7 years (mean). This analysis is restricted to the β-carotene and placebo arms (n = 14,569). The rate ratio (RR) of the common cold was modeled as a function of age at follow-up in the β-carotene arm compared with the placebo arm using Poisson regression. Results: Separate regression models in four subgroups of participants were constructed on the basis of the age of smoking initiation (#20 years versus $21 years) and baseline smoking level (5–14 versus $15 cigarettes/day). In three of the four subgroups, the effect of β-carotene was significantly modified by age. Among participants older than 70 years, the extent of smoking modified the effect so that β-carotene increased the incidence of colds in those who started smoking at an early age and smoked heavily: RR = 1.16 (95% confidence interval [CI]: 1.02–1.33), but decreased the incidence in those who started smoking at a later age and smoked less: RR = 0.76 (95% CI: 0.61–0.94). Conclusions: The strong evidence of heterogeneity in the β-carotene effect on the incidence of colds challenges the validity of cohort studies on nutrients, because they are usually based on the assumption of a uniform effect of the nutrient over the studied population.

nutrition and dietary supplements

The effect of &amp;beta;-carotene on common cold incidence is modified by age and smoking: evidence against a uniform effect in a nutrient&amp;ndash;disease relationship