Adverse circulatory effects of passive smoking during infancy: surprisingly strong, manifest early, easily avoided.

ABSTRACT

AIM: To compare blood pressure reactions (BPR) of infants to mild stress for evidence of adverse cardiovascular effects of passive exposure to tobacco smoke during pregnancy and early infancy. METHODS: An observational field study conducted in Crete. We compared 4- to 6-month olds of lifelong nonsmokers minimally (controls, n = 9) or frequently exposed to tobacco smoke (passive smokers; n = 10) with those born to habitual smokers (n = 6). Smoke exposure was verified biochemically (urine cotinine each trimester and at study). We recorded beat-to-beat blood pressure (BP) during brief repositioning manoeuvres performed during a daytime nap and analysed BPR (% change in BP during head-up tilt) for associations with maternal and infant cotinine. RESULTS: We observed a 20-fold difference between BPR of infants of controls versus passive smokers - exceptional given number of infants (α error/confidence level <10% i.e. power >90%). The BPR declined linearly as the infant's (but not mother's) cotinine level rose (p = 0.04), indicating abnormal BPR was caused mainly by postnatal smoke exposure. Infants of active smokers differed from those of passive smokers. CONCLUSION: Cardiovascular effects of passive smoking by a newborn infant manifest early on and are exceptionally strong. They can be largely avoided by keeping the home smoke rigorously free.