In the current study conducted among Iranian adolescents, we investigated the association of developmental patterns of BMI and WC with the adulthood cIMT as a contributor to subclinical atherosclerosis. The results of our study demonstrated that subjects of the high-increasing BMI trajectory group have significantly higher cIMT in adulthood. Accordingly, among WC trajectory groups, subjects of moderate-increasing and high-increasing groups have both higher cIMT in contrast to the low-stable WC trajectory group. Compared to the low-stable BMI trajectory, for high cIMT, the high-increasing trajectory increased the risk by approximately 3-fold. Also, the moderate-increasing and high-increasing trajectories of WC increased the risk of high adulthood cIMT, approximately 2- and 3-fold, respectively, in contrast to the low-stable WC trajectory group.
The subjects of our study were grouped into three categories based on BMI trajectory and WC trajectory, which represented the substantial heterogenicity of BMI and WC dynamic changes during over 20 years of follow-up through childhood to early adulthood. Several other studies with the same approach, utilizing latent class modeling, reached different numbers of WC and BMI trajectory groups, which were labeled to the pattern of dynamic changes and ranged from two to 6 groups, in different studies. (25, 26, 35–39) Also, the same number of BMI trajectory groups in our study was defined in some previous studies with the follow-up of subjects from childhood to adulthood. (25, 36, 37, 39)
Childhood overweight/ obesity is defined to be a major risk factor for adulthood obesity. The results of a systematic review study by Singh et al (6) showed that overweight and obese youth have an increased risk of being overweight during adulthood. Preventing overweight and obesity from an early age should be considered a major public health priority because, not only once an individual becomes obese, they are unlikely to return to normal body weight, but also childhood overweight and obesity can be an independent risk factor of cardiometabolic health during adulthood. (17, 18) Also, the cardiovascular consequences of obesity are shown to be cumulative and the duration of obesity is a strong predictor of CVD outcomes. (13, 26, 40–42)
The dynamic and cumulative consequences of overweight/ obesity, as reflected in BMI or WC trajectory, are associated with many cardiometabolic risk factors and also cardiovascular outcomes. In the study of Blond et al (37) higher BMI trajectories in childhood were associated with worse HDL, glucose homeostasis, total cholesterol, and triglyceride levels in adulthood. In another study on the Chinese population, the ratio risk of hypertension, type 2 diabetes mellitus, high-risk triglycerides, and high-risk HDL were more than 3.0 during adulthood among the high-increasing childhood BMI trajectory group. (36) Among other cardiometabolic risk factors, higher risk of hypertension incidence (20, 43, 44), metabolic syndrome (39), unfavorable levels of trunk fat (45), insulin (45), HDL (21, 45), left ventricular mass (25, 45), high plasma glucose (20) and incidence of diabetes, in adulthood are significantly associated with higher BMI trajectories during childhood.
Furthermore, among cardiovascular outcomes, the correlations between high BMI trajectories in adulthood and elevated lifetime risk of cardiovascular disease, stroke, and myocardial infarction were observed in a previous study. (42) In the study of Tirosh et al, BMI trajectories of adolescence to adulthood were measured, in which the hazard ratio of angiography-proven coronary heart disease was 5.42 in elevated adolescence BMI trajectory in multivariate model adjustment that stayed significant after adjustment for BMI at adulthood. (22) Correspondingly, WC trajectory is also correlated to the incidence of hypertension (27), level of diastolic and systolic blood pressure (46), incidence of diabetes (28) and also the incidence of cardiovascular disease. (26)
The adverse effect of youth overweight/ obesity is also reflected in adult pre-atherosclerosis and it may not be reversible even with weight normalization later in life. (47) The results of our study indicated that both WC and BMI trajectories from childhood to early adulthood are predictors of cIMT in adulthood. The study of Buscot et al (38) demonstrated that trajectories of worsening or persisting obesity from childhood to adulthood are associated with higher cIMT levels in adulthood. Even participants who resolved their childhood overweight/ obesity had an elevated risk of increased cIMT in adulthood. (38) Consistent with this study, our results specify that higher BMI and WC trajectories have a higher risk of high cIMT in adulthood (OR = 1.4, p = 0.17 and OR = 3.1, p = 0.003 for moderate-increasing and high-increasing BMI trajectories, respectively; and OR = 1.8, p = 0.039, and OR = 3.3, p = 0.003 for moderate-increasing and high-increasing WC trajectories, respectively, in contrast to low-stable trajectory). Although the moderate- and high-increasing WC trajectory group had significantly higher cIMT, this association is only significant among the high-increasing BMI trajectory group, but not moderate-increasing BMI trajectory. In the study of Hao et al (25), with the same BMI trajectory groups as our study, childhood BMI trajectory was significantly associated with adulthood cIMT after adjustment in a multivariate model for covariates (ß=0.014, p = 0.043 and ß=0.034, p = 0.001 for moderate increasing and high-increasing BMI trajectory, respectively); but it does not remain significant after adjustment for baseline BMI (p = 0.354 for moderate increasing; p = 0.250 for high-increasing BMI trajectory). In our study, the significance of the association between BMI/ WC trajectories and cIMT does not alter after adjustment for baseline BMI (ß=0.014, p = 0.043 and ß=0.034, p = 0.001 for moderate increasing and high-increasing BMI trajectory, respectively).
The current study has several strengths; the study is longitudinal and a follow-up long enough to examine the heterogeneity in BMI trajectories from childhood until early to mid-adulthood that allowed us to evaluate the effect of trajectories on endpoint cIMT. Second, LCGA, as a standard method to identify trajectories, involves several criteria in the identification of qualitatively distinct trajectories, selecting the best fitting model and predicting individual class membership from the available data and can deal with missing at random assumption. Regarding limitations of the study, our data were obtained from a metropolitan city of Iran and may not be national or to other population representatives. Second, only participants with available cIMT data were eligible for the study. Third, due to the limited sample size, we might not be able to capture all trajectory patterns. More studies with large sample sizes should be performed to confirm our results.
In conclusion, our study resulted that a high-increasing trajectory of childhood BMI and moderate- high-increasing trajectories of childhood WC is associated with higher cIMT and higher risk of high-cIMT. These data suggested that regular monitoring and screening of BMI and WC trajectory from childhood may improve the identification of individuals with high risks of cardiovascular disease and implement more accurate targeted strategies of prevention.