The current study aimed to evaluate the trajectory patterns of women’s BMI and to determine the association between these patterns with cardiovascular risk factors at both individual and familial levels. Using six measurements of women's BMI during a 20 years follow-up period, three steady patterns of BMI were identified, including normal, overweight, and obese. Our findings indicated that women in both overweight and obese trajectories were more likely to have HTN, DM, and dyslipidemia. In addition, men with obese spouses showed a higher rate of HTN and DM. In terms of mother-offspring relationship, the odds of obesity in offspring with overweight and obese mothers were higher than those whose mothers were normal weight.
Few studies investigated developmental trajectories of BMI in particular among women. In this novel longitudinal study, we assessed trajectory patterns of BMI among Iranian women. The model classified individuals in three rising BMI patterns. The current findings were consistent with world health organization (WHO) cut-off points for BMI categorization (47). Although there is no comparable data, we compared with other studies on BMI patterns in specific life periods. A study conducted among the Chinese population aged 6–60 years identified a continuous increase of BMI in all groups of BMI (48). Some studies indicated less variability in the BMI trajectories in midlife in the total population as well as women (49–51), whereas another study reported different patterns during middle age (52). A study conducted among Australian women showed significantly three distinct BMI patterns, which was similar to our findings (53). There is only one study in Iran that determined two patterns of BMI; however, their sample included adolescents (36).
In addition, we linked the trajectory pattern of women’s BMI to several cardiovascular risk factors, including high blood pressure, high blood glucose, obesity, and dyslipidemia. Our findings indicated that women in both overweight and obese trajectories were more likely to have HTN, DM, and dyslipidemia, suggesting the importance of early intervention. Previous studies have illustrated that an elevated BMI in women contributes to a high risk for DM, HTN, and high-risk HDL cholesterol, consistent with our results (54–57). In contrast, another study indicated that a rising trend of BMI was not associated with high blood pressure (58). This finding may have been due to other related factors with blood pressure, such as smoking (58). Compared with the current study, different statistical methods applied among these studies and the limited time points would also be considered. Additionally, differences among populations such as ethnicity, culture, and socioeconomic status (SES) may also explain this inconsistency (59).
In terms of spousal association, our study showed that men with obese spouses showed a higher rate of HTN and DM. There was no comparable data regarding the effect of one spouse’s weight trajectories on cardio-metabolic risk factors in the other spouse. However, in line with our results, some cross-sectional studies considered the spousal concordance in chronic diseases. Studies showed that husbands' health status is influenced by their wives who get chronic diseases (60), and changes in weight status of husbands were linked to their spouses’ DM (61). Moreover, another study showed this association in the other direction in which the weight gain in wives increased the risk of type 2 diabetes in their husbands (21). The reasons may be explained by a predominant role of wives as caregivers in the families (62). Regarding lifestyles and health management, husbands may be more dependent on their spouses, which husbands with obese spouses are more likely to have chronic diseases such as obesity, HTN, and DM (63).
Regarding the association between women’s BMI and CVD risk factors in their offspring, the current study reported mothers with high BMI values are predicted to have obese children, which was consistent with previous studies (64). Moreover, some cross-sectional studies in Iran and other countries reported that children with obese parents had significantly higher odds of obesity and elevated BP (18, 65, 66). This association is more attributed to the mother-offspring relationship (67). This may be due to genetic/epigenetic factors, shared family environment, and health-related attitudes of parents in particular mothers because of their main roles in the family, which influence their children's behaviors (68). Although a number of studies reported the association between parental obesity and HTN (69), DM (70) of their offspring, a study did not find any significant association which was in line with the current results (70, 71).
This study has several strengths. This is the first report in the world, which addressed the association of BMI trajectories with cardiovascular risk factors at both individual and familial levels. The current study was conducted among the Iranian population with a relatively large sample and a long follow-up period. From an analytical point of view, LCGA was applied as a precise longitudinal method to characterize distinct BMI trajectory patterns. However, several limitations of this study need to be considered. First, the sample was limited to a metropolitan city and cannot be generalized to a rural population. Secondly, some potential predictors of cardiovascular risk factors such as genetic susceptibility and environmental conditions such as air pollution (72, 73) were not available in the current study.