See article vol. 24: 1231–1241
The American Heart Association reported that exposure to second-hand tobacco smoke (SHS) in childhood, mainly SHS through parental smoking, was associated with future adverse cardiovascular health1). However, the patho-physiological mechanism by which SHS affects cardiovascular health is not fully understood.
In this issue of the Journal of Atherosclerosis and Thrombosis, Wang et al. used 31-year follow-up data for 2,511 participants from the Cardiovascular Risk in Young Finns Study, to explore the association between childhood exposure to parental smoking and low-grade inflammation in adulthood, which was defined as a high-sensitivity C-reactive protein (hsCRP) level of greater than 0.3 mg/dl2). Based on information obtained from a self-reported parental questionnaire, they defined passive smoking at baseline as one or both parents smoking. Compared with off-springs with non-smoking parents, those who had a smoking mother or father showed an increased risk of elevated hsCRP level (relative risk (RR) adjusted for cardiovascular risk factors and participants' own smoking status in childhood and adulthood = 1.3, with a 95% confidence interval (CI) of 1.0–1.8). In addition, the authors observed that the high hsCRP risk for mother-only smoking (RR = 2.4; 95% CI = 1.3–4.2) was greater than that for father-only smoking (RR = 1.6; 95% CI = 1.2–2.3) and for both-parent smoking (RR = 1.4; 95% CI = 0.9–2.0).
An elevated CRP level, which is a systemic inflammatory marker, is known to reflect the development of atherosclerotic lesions3, 4). The J-STARS trial showed that statin treatments led to a decrease in the hs-CRP level among patients with a history of noncardiogenic ischemic stroke5). As CRP is a marker of atherosclerosis, an increase in the CRP level typically precedes the occurrence of cardiovascular disease3, 6). In addition, there is evidence that hsCRP was associated with the risk of chronic kidney disease7). Therefore, the results reported by Wang et al suggested that exposure to parental smoking in childhood has the potential to cause future cardiovascular disease via the development of atherosclerosis. However, their study had some limitations. First, the reason behind the stronger effect of mother-only smoking compared with both-parent smoking was unclear. Second, the authors did not obtain information on maternal smoking during pregnancy (exposure to SHS in utero). The statement from the American Heart Association noted that it was still unclear whether exposure to SHS in utero, or in childhood, or in both stages, was important for future cardiovascular health1). In addition, there were unmeasured factors that may have confounded the observed association; among them, the use of anti-inflammatory medication and exposure to air pollutants8). Notwithstanding these limitations, however, the study by Wang et al. provided additional evidence regarding future cardiovascular effects of childhood exposure to SHS.
To our knowledge, few prospective Japanese studies have examined the effect of exposure to SHS in childhood on cardiovascular sequence. The Longitudinal Survey of Babies in the 21st Century, conducted by the Japanese Ministry of Health, Labour and Welfare, registered approximately 47,000 6-month-old children in 2001, and followed them until the age of 13. Compared with children not exposed to parental smoking when they were 6 months old, children whose mothers or fathers had smoked indoors had an elevated risk of overweightness/obesity from 2 to 13 years old9). Epidemiological evidence, in this regard, is expected for Japanese individuals whose cardiovascular risk profile differs from that of the Western population.
Conflict of Interest
None.
References
- 1). Raghuveer G, White DA, Hayman LL, Woo JG, Villafane J, Celermajer D, Ward KD, de Ferranti SD, Zachariah J, American Heart Association Committee on Atherosclerosis, Hypertension, and Obesity in the Young of the Council on Cardiovascular Disease in the Young; Behavior Change for Improving Health Factors Committee of the Council on Lifestyle and Cardiometabolic Health and Council on Epidemiology and Prevention; and Stroke Council. Cardiovascular consequences of childhood secondhand tobacco smoke exposure : Prevailing evidence, burden, and racial and socioeconomic disparities: A scientific statement from the American Heart Associations. Circulation, 2016; 134: e336-e359 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2). Wang D, Juonala M, Viikari JSA, Wu F, Kähönen M, Raitakari OT, Magnussen CG: Exposure to parental smoking in childhood is associated with high C-reactive protein in adulthood: The Cardiovascular Risk in Young Finns Study. J Atheroscler Thromb, 2017; 24: 1231-1241 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 3). Pearson TA, Mensah GA, Alexander RW, Anderson JL, Cannon RO, 3rd, Criqui M, Fadl YY, Fortmann SP, Hong Y, Myers GL, Rifai N, Smith SC, Jr., Taubert K, Tracy RP, Vinicor F: Markers of inflammation and cardiovascular disease: Application to clinical and public health practice: A statement for healthcare professionals from the Centers for Disease Control and Prevention and the American Heart Association. Circulation, 2003; 107: 499-511 [DOI] [PubMed] [Google Scholar]
- 4). Nagasawa S, Ohkubo T, Masaki K, Barinas-Mitchell E, Miura K, Seto TB, El-Saed A, Kadowaki T, Willcox BJ, Edmundowicz D, Kadota A, Evans RW, Kadowaki S, Fujiyoshi A, Hisamatsu T, Bertolet MH, Okamura T, Nakamura Y, Kuller LH, Ueshima H, Sekikawa A, ERAJUNP Study Group : Associations between inflammatory markers and subclinical atherosclerosis in middle-aged White, Japanese-American and Japanese Men: The ERAJUMP Study. J Atheroscler Thromb, 2015; 22: 590-598 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 5). Kitagawa K, Hosomi N, Nagai Y, Kagimura T, Ohtsuki T, Origasa H, Minematsu K, Uchiyama S, Nakamura M, Matsumoto M, J-STARS Investigators : Reduction in high-sensitivity C-reactive protein levels in patients with ischemic stroke by statin treatment: Hs-CRP Sub-Study in J-STARS. J Atheroscler Thromb, 2017; 24: 1039-1047 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 6). Iso H, Noda H, Ikeda A, Yamagishi K, Inoue M, Iwasaki M, Tsugane S: The impact of C-reactive protein on risk of stroke, stroke subtypes, and ischemic heart disease in middle-aged Japanese: the Japan public health center-based study. J Atheroscler Thromb, 2012; 19: 756-766 [PubMed] [Google Scholar]
- 7). Kubo S, Kitamura A, Imano H, Cui R, Yamagishi K, Umesawa M, Muraki I, Kiyama M, Okada T, Iso H, Circulatory Risk in Communities Study Investigators : Serum albumin and high-sensitivity C-reactive protein are independent risk factors of chronic kidney disease in middleaged Japanese individuals: the Circulatory Risk in Communities Study. J Atheroscler Thromb, 2016; 23: 1089-1098 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 8). Michikawa T, Okamura T, Nitta H, Nishiwaki Y, Takebayashi T, Ueda K, Kadota A, Fujiyoshi A, Ohkubo T, Ueshima H, Okayama A, Miura K, NIPPON DATA2010 Research Group : Cross-sectional association between exposure to particulate matter and inflammatory markers in the Japanese general population: NIPPON DATA2010. Environ Pollut, 2016; 213: 460-467 [DOI] [PubMed] [Google Scholar]
- 9). Ministry of Health, Labour, and Welfare, Japan: Special report from the Longitudinal Survey of Babies in the 21st Century, 2001. 2017. Available: http://www.mhlw.go.jp/toukei/saikin/hw/syusseiji/13tokubetu/index.html [Accessed 7 June 2017]