There is evidence of high prevalence of IHD (according to epidemiological criteria) and its RFs in the population of Novosibirsk, a capital of Western Siberia. In this city, a young population (25–44 years of age) was last analyzed during the WHO project MONICA in the1990s [11–13].
Our results were obtained via a medical examination of the 25–44-year-old age group in Novosibirsk during 2014–2015. The results showed that at present, the prevalence of definite IHD in the study population (3.36%) and in its male (2.8%) and female (3.9%) subpopulations is not high.
It is known that more than half of young adults even at the age of 18–24 years have at least one RF of IHD .
We studied quantitative data on IHD RFs and data on the prevalence of IHD RFs, such as smoking, elevated BMI, elevated WC, AH presence, low physical activity, and elevated blood levels of LDL-C, non-HDL-C, and TG sin older subjects: 25–44 years. The prevalence of the aforementioned RFs in the study population ranged from 25–85%. All quantitative data on the analyzed RFs of IHD were higher in males than in females. In addition, the prevalence of the studied IHD RFs turned out to be higher among males than females, except for the “elevated WC” RF (indicating abdominal obesity), whose prevalence was not significantly different between males (42%) and females (45%). As for the excess body weight in general, it was found to be 1.3-fold higher among males than among females.
While discussing this result, we should point out that obesity occurs more often among patients with early development of IHD and is an independent predictor of coronary atherosclerosis at a young age, as revealed in some studies. In particular, this pattern was demonstrated in a comparison of the prevalence of RFs among patients hospitalized with acute MI at age younger and older than 50, in a registry containing 1199 patients . The link of obesity with atherosclerosis at a young age was demonstrated in a study on autopsies of 3 000 subjects aged 15–34 years who died of non-cardiological causes . In the Framingham study, it was shown that the contribution of obesity to the development of IHD in middle-aged people may be as high as 23% of the cases among males and 15% of the cases among females .
In our study population, the prevalence of the analyzed IHD RFs (except for cigarette smoking) was found to be not different between the groups with and without IHD. The prevalence of smokers was 1.7-fold higher in the no-IHD group than in the group with IHD. Our multivariate logistical regression analysis also uncovered an inverse association of smoking (independent of age, sex, and other analyzed RFs) with the relative risk of definite IHD in the study population (25–44-year-olds in Novosibirsk). We explain this finding, which contradicts known classical data, by the insufficient number of IHD cases (a total of 49 subjects, 18 males and 31 females) in our study.
Indeed, all the data from the international literature point to a rather significant role of smoking in IHD development and complications. It is believed that smoking is the most prevalent RF of early IHD. According to Cole J.H. and coworkers, the number of smokers among IHD patients under 45 years ranges from 60%to 90%, whereas among patients older than 45 years, from 24%to 56% .
In a meta-analysis including 14 international randomized studies on IHD, among76716 MI patients with ST segment elevation, 35527 patients with unstable angina pectoris/MI without ST segment elevation, and 10215 patients who underwent percutaneous coronary interventions, researchers analyzed the prevalence of 4 RFs (smoking, diabetes mellitus, AH, and hyperlipidemia) depending on sex and age. In the majority of younger patients, at least one RF was noted, with the most frequent one being smoking: 72% frequency among subjects younger than 45 years, both in males and in females .
In a study on a registry intended for observation of 892 patients with acute MI with ST segment elevation who underwent their first percutaneous coronary intervention, there were 78% of smokers among the patients aged 18 to 34 years, and 23% of smokers in the whole study population; the percentage of smokers decreased with the increasing age at MI diagnosis .
Kafadar D. and colleagues have examined 235 patients with coronary-angiography–verified coronary atherosclerosis. Active smokers showed the highest mean levels of TGs in the blood, whereas nonsmokers were reported to have the highest mean HDL-C concentrations .
Christus T. and coworkers have examined 200 males younger than 35 years with IHD diagnosed by coronary angiography and concluded that the main RFin this population is cigarette smoking .
As compared with the total number of publications about the adverse impact of cigarette smoking on the development of CVDs in the world literature, there are only a few papers where the results defy the traditional findings, for example, the study by Li G. and colleagues . They examined a Chinese population aged 20–80 years (1248 subjects) and concluded that sex- and age-adjusted BP is lower in smokers than in nonsmokers or former smokers. There was no significant dose-dependent influence of smoking on sex- and age-adjusted BP. Furthermore, smoking cessation was significantly associated with a higher risk of hypertension.
Because none of the RFs analyzed by us, except for smoking, manifested an apparent association with the relative risk of IHD, and because the cigarette smoking analysis yielded the “paradoxical” result, we then investigated the link of IHD with socioeconomic factors whose influence on IHD development has been actively discussed in the last decades .
We performed a multivariate logistical regression analysis of the socioeconomic factors in relation to the risk of definite IHD in our study population (25–44-year-olds in Novosibirsk) and in its male and female subpopulations. Statistically significant results were obtained only in the male subpopulation. We identified age-independent associations of the occupation type and marital status (which correlated with smoking), with the relative risk of early IHD in males aged 25–44 years. It was found that among divorced males aged 25–44 years, the probability of the presence of early IHD is 5-fold higher, whereas among males occupationally engaged in heavy manual labor, it is 3.5-fold higher.
Our results are consistent with data from other studies. For example, the influence of marital status on the frequency of CVDs and prognosis after CVD was assessed in a meta-analysis of 34 studies involving more than 2 million participants. In comparison with married participants, the absence of marriage (never married, divorced, or widowed) correlated with a higher risk of CVDs, IHD, death from IHD, and death from stroke. Divorce was associated with a higher risk of IHD both in males and in females .
Leisure time physical activity is a widely recognized protective factor against cardiovascular mortality. Participants of a prospective epidemiological study on MI (PRIME; n = 9758; age 50 to 59 years), who did not have IHD at the beginning of the study, were observed for 5 years: the researchers registered 167 cases of severe IHD and 154 cases of tension angina pectoris. A beneficial effect of leisure time physical activity was noted among the subjects who did not report high-intensity activity, in France and Northern Ireland. By contrast, increasing the level of leisure time physical activity was associated with a higher risk of tension angina pectoris in both countries .
In the CORDIS study, investigators analyzed the influence of leisure time physical activity and of heavy physical activity associated with one’s job (occupational heavy manual labor) on cardiovascular mortality among males (4819 subjects) during 22-year prospective observation. It was occupational heavy manual labor that posed the highest risk of death, including IHD-related mortality. Those authors concluded that heavy manual labor at one’s job is bad for health .
Thus, our data suggest that among 25–44-year-old males in Novosibirsk, the relative risk of IHD (namely, early IHD, manifesting itself before 45 years of age) directly correlates with occupational heavy manual labor and unfavorable marital status but is inversely associated with smoking. In our opinion, these results undoubtedly require further research.