**4. Association of hair cortisol with cardiometabolic risk factors**

#### **4.1 Hypertension**

Hypertension is also known as high or raised blood pressure, in which the blood vessels have persistently raised pressure. A patient is diagnosed with hypertension when the systolic blood pressure (SBP) is above or equal to 140 mm Hg and/or diastolic blood pressure (DBP) is above or equal to 90 mm Hg [20]. If left unmanaged, hypertension can lead to a heart attack, an enlarged heart, and heart failure [21]. Hypertension can also result in kidney failure, blindness, rupture of blood vessels, and cognitive impairment. Hypertension is a critical public health and clinical condition affecting billions worldwide, including approximately the 2 million Americans diagnosed annually [22]. Hypertension is one of the most prevalent risk factors for almost all cardiovascular diseases [23].

Chronic psychosocial stress is believed to increase the risk of hypertension through sustained exposure to elevated cortisol levels [21]. Cortisol is essential for maintaining normal blood pressure but, in excess, produces hypertension [24]. In 2002, the Prospective Studies Collaboration published a meta-analysis based on 61 cohort studies showing that the risk of CVD increased steadily with progressively higher levels of baseline SBP and DBP; a 20 mm Hg higher level of SBP and a 10 mm Hg higher level of DBP resulted in a 2-fold higher BP-related absolute risk of CVD [25]. While research exploring an independent association between HCC and hypertension is still a new research area, several cross-sectional studies found a positive correlation between hair cortisol and hypertension [18, 21]. Still, the data on the relationship between blood pressure and hair cortisol level is inconsistent. While some studies reported a positive association between mean arterial or systolic blood pressure and HCC, other studies failed to demonstrate a relationship. In addition, Feller et al. found no association between prevalent hypertension and HCC and a negative relationship between objectively measured diastolic blood pressure and HCC. Hypertension prevalence was 2.23 times higher in participants with CVD [21].

#### **4.2 Obesity**

Cardiovascular disease (CVD) is one of the primary causes of increased morbidity and mortality in people with obesity [26, 27]. Obesity is defined as an excessive accumulation of body fat, with the amount of this excess fat being directly responsible for most obesity-associated health risks [27]. Although body mass index (BMI) is the established clinical measurement to estimate CVD risk associated with excess body weight, increasing evidence suggests that abdominal obesity, as assessed by the waist-hip ratio (WHR), could represent a better marker of CVD risk than BMI [28].

The incidence of obesity is increasing at a rapid and concerning rate in most regions worldwide, with direct consequences on the risk of developing several chronic diseases such as systemic hypertension [29] and type 2 diabetes [30]. More seriously, obesity usually occurs with a cluster of metabolic disturbances such as impaired glucose metabolism, atherogenic dyslipidemia, and hypertension, and obese individuals have an increased risk of CVD [26]. Interestingly, perceived societal stigma due to weight discrimination was shown to contribute to HCC [31], complicating the association of elevated cortisol with obesity. Still, HCC was associated with higher BMI in obese individuals (BMI > 30 kg/m2) compared to average weight (BMI: 18.5–24.9) and nonobese overweight (BMI: 25.0–29.9) people [19]. A meta-analysis confirmed the positive associations between HCC and stress-related anthropometric measures (BMI and WHR) and reported a 9.8% increase in HCC per 2.5 points BMI [18].

#### **4.3 Dyslipidemia**

Dyslipidemia is a common metabolic disorder and an established risk factor for cardiovascular disease [32]. The condition is characterized by high-risk lipid levels with an increased level of serum total cholesterol (TC), triglycerides (TG), lowdensity lipoprotein cholesterol (LDL-C), or a decreased concentration of serum high-density lipoprotein cholesterol (HDL-C) [33]. Dyslipidemia is closely linked with obesity, a disease characterized by an adverse effect on lipoproteins a known cardiometabolic risk factor [34].

The relationship between hair cortisol with lipids varied considerably across studies. The MASHAD study, a prospective cohort population study, found that increased serum total cholesterol levels were positively associated with absolute CVD risk among men and women [33]. However, after adjusting for confounding factors, high serum TC only significantly increased the risk of myocardial infarction in men. Kuehl *et al*. reported a positive association between triglycerides and HCC [35]. Another study found a positive association between low-density lipoprotein cholesterol (LDL-C) and HCC [3]. Since dyslipidemia is one of the main cardiovascular risk factors, further research is needed to examine chronic cortisol exposure and its effect on lipid metabolism.

#### **4.4 Diabetes**

Cardiovascular diseases are the most common cause of morbidity and mortality among patients with diabetes mellitus [36]. More than 90% of people with diabetes mellitus suffer from type 2 diabetes (T2D), a disease characterized by hyperglycemia, insulin resistance, and impaired glucose tolerance [37]. T2D and CVD have several shared characteristics; both conditions increase with age, are associated with an adverse lipid profile, obesity, and a sedentary lifestyle, and lifestyle modifications of common risk factors can reduce the risk of both [38]. Generally, patients with T2D also display other comorbidities such as obesity, hypertension, and dyslipidemia, increasing the risk for CVD [36].

*The Association of Hair Cortisol and Cardiometabolic Risk Factors in Cardiovascular… DOI: http://dx.doi.org/10.5772/intechopen.108356*

Recently the CAPTURE study, a study assessing the prevalence of established CVD and its management in adults with T2D across 13 countries and five continents, reported that CVD was prevalent in 34.8% of patients with T2D [39]. Elevated cortisol levels are consistently associated with glycated hemoglobin, the diagnostic measure of T2D [18, 40] or diabetes [41–43]. Manenschijn *et al*. reported that HCC is associated with CVD and diabetes [13]. Since CVD and T2D share so many characteristics, further study of HCC measurements could be interesting in trying to discriminate between the two diseases or show that they are inextricably linked.
