Cardiovascular diseases were responsible for nearly one-third of total deaths worldwide in 2016. It is predicted that cardiovascular diseases will be the cause of over 23 million deaths globally by 2030 (1, 2). Risk factors such as body mass index (BMI), systolic blood pressure, low-density lipoprotein cholesterol, and diabetes constitute a percentage of the prevalence and occurrence of cardiovascular diseases (3). The Global Burden of Disease group has estimated that elevated BMI levels were associated with 4 million deaths in 2015, with two-thirds of these attributed to cardiovascular diseases (4).
Type 2 diabetes is a major risk factor for cardiovascular diseases, and there is an association between obesity and type 2 diabetes. Since obesity is often accompanied by high blood pressure and dyslipidemia, many high-risk patients with obesity exhibit a set of metabolic and cardiovascular risk factors (5).
Obesity and 25-hydroxyvitamin D deficiency both affect each other. In recent years, the amount of studies investigating the role of 25-hydroxyvitamin D in biological pathways has been increasing (6). 25-hydroxyvitamin D deficiency has been associated with an increased risk of diabetes, arterial hypertension, heart failure, peripheral arterial disease, autoimmune and inflammatory diseases, immunodeficiency, and increased mortality (7). Also, 25-hydroxyvitamin D plays an essential role in the regulation of glucose homeostasis, mechanisms of insulin secretion, and obesity-related inflammation (8).
25-hydroxyvitamin D is a prohormone essential for skeletal and muscular health, the natural immune system, and various other bodily functions (9). It has recently been proven to play a role in immunity and cardiovascular health as well (10). Dobnig et al related low 25-hydroxyvitamin D levels in a cohort of subjects scheduled for angiography to increased all-cause and CV mortality (11). Studies have shown that the risk of developing heart failure increases in individuals with a deficiency in 25-hydroxyvitamin D (10). Additionally, 25-hydroxyvitamin D deficiency is associated with an increase in blood pressure (12). A significant negative correlation was found in a study between 25-hydroxyvitamin D levels and systolic blood pressure (13). Another study indicated that obesity could reduce the effectiveness of 25-hydroxyvitamin D supplementation in obese patients, with serum 25-hydroxyvitamin D concentrations in obese individuals being 17.38 nanomoles per liter less than those with normal weight (14).
It is generally believed that military personnel undergo vigorous sports and high-intensity physical training and have a lower prevalence of metabolic syndrome and hyperuricemia. Although the results of epidemiological studies show that the capacity for exercise and physical training is higher in military people, the risk factors for cardiovascular and metabolic diseases are not lower than in the general population (15). Despite weight and fitness standards for military personnel, these individuals are not immune to the obesity epidemic and its associated health effects. Studies have shown that soldiers gain as much weight each year as civilians (16).
Military forces play a crucial role in defending, maintaining the security, and ensuring the stability of a nation. These individuals are significantly exposed to various injuries and specific diseases due to their missions, duties, and occupational requirements (17). Many of these conditions, upon occurrence, require regular and continuous medical care, and controlling the factors leading to them can be challenging in military settings (18).
Low 25-hydroxyvitamin D status is common in individuals engaged in regular intense physical activity, especially when accompanied by psychological stress, insufficient nutrition, or sleep disorders (19). This places military personnel in a high-risk category, with significant negative consequences for their health (19). Therefore, considering the importance of the health of military personnel, this study aimed to investigate the relationship between 25-hydroxyvitamin D levels and cardiovascular risk factors, taking into account the obesity status of individuals, among military personnel in Tehran in 2023.