The present study found that 96.5% of the military personnel participating in this study had FRS less than 10%. On the other hand, 2% of these people showed moderate risk (10–19%) and 1.5% of participants had a risk above 20%. Further, the relationships examined in this research suggested that HDI had no significant relationship with FRS, but dietary sodium intake indicated a significant positive relationship with FRS. These results were found after controlling the confounding variables.
Population studies suggests that prevalence of CVD as well as the risk factors of CVD are growing in the military personnel (11). Meanwhile, past evidence suggests that controlling CVD risk factors can significantly reduce the development as well as mortality caused by this disease across the military population (12). In this regard, various prospective studies have been conducted worldwide to predict the risk of developing CVD across the military population. A result found in the present study showed that a wide range (96.5%) of the military personnel participating in this study had a low 10-year risk of CVD. Confirming this finding, the study by Al-Dahi et al. performed on 10500 military personnel in Saudi Arabia also showed that only 9.1% of the participants had a 10-year risk of CVD above 10%, while 90.9% of the participants showed a risk lower than 10%; the mean FRS across the military personnel participating in that study was 4.5 (22).
Elsewhere, prevalence of CVD risk factors and then 10-year risk of CVD among men in the Belgian military was examined by Mullie et al. (2010). Prevalence of obesity across the official officers, unofficial officers, and soldiers was 5.6%, 15%, and 19.5%, respectively. On the other hand, only about 8.5% of the officers had a 10-year risk of CVD above 5%. Also, high-risk participants had age younger than 40, and 12.5% of official officers and 19.7% of unofficial officers had smoking habits (23). However, the results of the study by Grósz et al. also challenge the findings of the studies mentioned above. The research by Grósz et al. was performed to determine the 10-year risk level of CVD among 250 male military pilots. They found that half of the participants had a five-year risk of CVD above 2.5%; this number did not exceed 15–20% even in the high-risk age group. In addition, the level of CVD risk factors among the military pilots participating in that study was as follows: insufficient physical activity: 23.9%, smoking: 31.7%, high blood pressure: 14.7%, obesity: 40.8% (24). The discrepancies across all these findings can be examined from different aspects. Bearing in mind that smoking can significantly increase risk of CVD, the level of smoking in the present study was only 4.2%, and in turn the 10-year risk of CVD was also significantly lower. However, in the study by Grósz et al. the level of smoking was around 31.7%, and hence the five-year risk of CVD was significantly higher. Further, BMI in our study was about 25 kg/m2, while 48.8% of the military pilots in the study by Grósz et al. had BMI > 25 kg/m2, with 40.8% of the participants considered obese. In addition, investigation of previous studies with discrepant results would suggest that the military personnel participating in the present study had a more desirable status regarding the blood pressure and total cholesterol, and thus showed lower FRS (23, 24). Based on the mentioned scenarios, again it seems that the results obtained in the present research are reasonably acceptable.
Another finding here showed that the HDI-2020 had no significant relationship with FRS among the military personnel, but increased dietary sodium intake as one of the HDI elements led to a significant rise in FRS. Although studies based on measuring the dietary quality using HDI among the military personnel are very limited, some researchers have conducted notable studies on examining the relationship between HDI and CVD risk as well as CVD induced mortality among other groups of people. Confirming the results of the present study, Mertens et al. who researched 1867 men found no significant relationship between HDI and incidence of CVD either. However, increase in HDI score had an inverse significant relationship with CRP as one of the CVD-risk factors. On the other hand, intake of calories, protein, carbohydrate, sodium, fiber, and fat had no significant difference across the HDI subgroups (25). A cohort study by Struijk et al. on 33671 healthy men and women in Netherlands in the 1990s showed no significant relationship between HDI and CVD risk (26). Further, the results of Atkins et al. on 3325 British 60-79-year-old man suggested that the mortality risk caused by CVD had no significant relationship with HDI score. Further, increased consumption of SFA, PUFA, protein, carbohydrate, sugar, fiber, fruits and vegetables had no significant effect on the incidence of CVD. However, increased dietary cholesterol intake, as one of the HDI elements, significantly augmented the mortality caused by CVD (27). On the other hand, Stefler et al. showed that higher HDI score was associated with a significant reduction in the mortality caused by CVD among 1855 elderly people in the Eastern Europe (14). Further, Knoops et al. reported that higher HDI score had an inverse relationship with all-cause mortality risk including CVD (28). The discrepancies across all of these investigations engender controversial assumptions. One of the assumptions is related to the type of elements examined by HDI-2020 in the present study. Some past research with incongruent results had also dealt with the original HDI assessment, while our study worked with the updated version of this index. One of the differences between these two versions is related to dietary sodium intake, which had not been mentioned in the original HDI, but the present study had considered the daily sodium intake as one of the elements of HDI. Meanwhile, investigation of the results of some other dietary quality indicators shows that increase in the level of some nutrients such as fruits and vegetables, fiber, and whole grains can reduce the risk of CVD, but the results of the present study did not confirm this claim. One of the mentioned assumptions can be due to insufficient consumption of these compounds by Iranian adults. This is because currently there is no comprehensive or exhaustive dietary guidelines for the Iranian population, and it seems some changes have occurred in the Iranian diet (4). Another assumption is related to gender and age of participants. Based on previous studies, women and the elderly have a higher HDI score compared to others (16). Considering the gender and average age of the participants in the present study, there is the assumption that HDI may not be adequately high across the military personnel. Thus, the low range of HDI score has resulted in minor influence of this index on the 10-year risk of CVD.
The main limitation of the present study was its nature, i.e. being cross-sectional, which can complicate extraction of causal relations between HDI and 10-year risk of CVD. Another limitation was gender of participants. Since the female military personnel claims a very minor percentage of the Iranian military community, thus the participants here were chosen from male individuals. Accordingly, the results obtained across the military personnel may be different among women. The strong points of this study were as follows: 1) the results have been obtained based on controlling the most important potential confounders, which has increased the validity of this study; 2) so far no study has been done on assessing the relationship between FRS and HDI score across the military personnel in Iran, and this study can be regarded as the first exploring this relationship in Iran.