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Articles by K. H Bonaa
Total Records ( 2 ) for K. H Bonaa
  R Clarke , J Halsey , S Lewington , E Lonn , J Armitage , J. E Manson , K. H Bonaa , J. D Spence , O Nygard , R Jamison , J. M Gaziano , P Guarino , D Bennett , F Mir , R Peto , R Collins and for the B Vitamin Treatment Trialists' Collaboration

Elevated plasma homocysteine levels have been associated with higher risks of cardiovascular disease, but the effects on disease rates of supplementation with folic acid to lower plasma homocysteine levels are uncertain. Individual participant data were obtained for a meta-analysis of 8 large, randomized, placebo-controlled trials of folic acid supplementation involving 37 485 individuals at increased risk of cardiovascular disease. The analyses involved intention-to-treat comparisons of first events during the scheduled treatment period. There were 9326 major vascular events (3990 major coronary events, 1528 strokes, and 5068 revascularizations), 3010 cancers, and 5125 deaths. Folic acid allocation yielded an average 25% reduction in homocysteine levels. During a median follow-up of 5 years, folic acid allocation had no significant effects on vascular outcomes, with rate ratios (95% confidence intervals) of 1.01 (0.97-1.05) for major vascular events, 1.03 (0.97-1.10) for major coronary events, and 0.96 (0.87-1.06) for stroke. Likewise, there were no significant effects on vascular outcomes in any of the subgroups studied or on overall vascular mortality. There was no significant effect on the rate ratios (95% confidence intervals) for overall cancer incidence (1.05 [0.98-1.13]), cancer mortality (1.00 [0.85-1.18]) or all-cause mortality (1.02 [0.97-1.08]) during the whole scheduled treatment period or during the later years of it. Dietary supplementation with folic acid to lower homocysteine levels had no significant effects within 5 years on cardiovascular events or on overall cancer or mortality in the populations studied.

  A Ulvik , M Ebbing , S Hustad , O Midttun , O Nygard , S. E Vollset , K. H Bonaa , J. E Nordrehaug , D. W Nilsen , H Schirmer and P. M. Ueland

Background: Smoking is associated with decreased concentrations of several antioxidant vitamins. We sought to determine the relation between circulating concentrations of selected B vitamins and smoking status, with particular attention to longitudinal associations.

Methods: We used baseline data from 2 B-vitamin intervention trials that included 6837 patients with ischemic heart disease. Smoking habits were ascertained by interview. Vitamins and metabolites, including the nicotine metabolite cotinine, were measured in plasma and serum by microbiological assays or gas/liquid chromatography–tandem mass spectrometry.

Results: The highest circulating concentrations of folate and pyridoxal 5'phosphate (PLP) and lowest concentrations of total plasma homocysteine, a functional marker of folate status, were observed for self-reported never smokers, followed by self-reported ex-smokers and current smokers (Ptrend < 0.001). Cobalamin and its functional marker methylmalonic acid were not associated with smoking status. Based on their low cotinine concentrations, we were able to identify a group of smokers that had abstained from smoking for 3 days or more. Compared with smokers with high plasma cotinine, smokers with low cotinine had significantly higher circulating concentrations of folate, PLP, and riboflavin (all P < 0.005), and this trend continued for ex-smokers, with increasing time since smoking cessation.

Conclusions: Smoking lowered circulating concentrations of folate, PLP, and riboflavin, but concentrations increased significantly after a few days of smoking cessation. We propose that short-term effects may be related to acute smoking-induced oxidative stress, whereas the longer-lasting effects among ex-smokers may reflect changes in diet and/or restoration of vitamin concentrations in tissue during the first few months to years after smoking cessation.

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