Chronic fatigue syndrome or Myalgic encephalomyelitis (CFS/ME) is a complex disorder characterized by severe and prolonged fatigue that is unalleviated by rest and not caused by any underlying medical or psychological condition [1]. It is an uncommon medical condition, with women being twice as prone to developing CFS/ME compared to men [2, 3]. Individuals with CFS/ME often experience cognitive impairment, sleep disturbances, and a range of other symptoms that can impact their quality of life [4]. The diagnosis of CFS/ME can be challenging due to limited understanding of the etiology, varying range of non-specific symptoms, and lack of objective assessment tools to aid in confirming diagnosis [5]. CFS/ME is associated with many comorbid conditions, mostly psychiatric, but there has been growing evidence of its association with cardiovascular disease [6].
Cardiovascular disease (CVD) is a leading cause of morbidity and mortality worldwide [7, 8, 9], and several studies have suggested that there may be an association between CFS/ME and CVD, with a reported increased prevalence of CVD in individuals with CFS/ME. In a study including over 500 individuals with CFS/ME, 25% reported a history of heart disease or hypertension, compared to 5% in the general population [10]. Another study found that a subgroup of individuals with CFS/ME had a higher prevalence of cardiomyopathy [11]. Furthermore, pooled prevalence from a systematic review and meta-analysis reported an estimate of 51.4% for any type of cardiac abnormalities in individuals with CFS/ME [12], a much higher prevalence compared to those without a diagnosis of CFS/ME.
The relationship between CFS/ME and CVD is not fully understood [6]. However, several mechanisms have been proposed to explain the association. Chronic inflammation has been implicated in both CFS/ME and CVD. Studies have shown that individuals with CFS/ME have higher levels of pro-inflammatory cytokines [13], and these are also associated with the development of atherosclerosis and CVD [14]. Additional studies have noted that individuals with CFS/ME have reduced stroke volume, with a significant inverse relation between cardiac output and the severity of the disease [15, 16]. Patients with CFS/ME were observed to have a small left ventricular size and low cardiac output, with marked orthostatic intolerance [17, 18, 19].
Furthermore, autonomic dysfunction is frequently seen in individuals with CFS/ME and is associated with an increased risk of CVD [20]. In other studies, CFS/ME was characterized by reduced blood pressure and systolic blood pressure variability. At the same time, oxidative stress, which is elevated in CFS/ME, is believed to potentially contribute to the development of CVD [21, 22, 23]. These physiological changes contribute to some of the symptoms experienced by individuals with CFS/ME, including extreme fatigue [6, 22].
The association between CFS/ME and CVD has potential clinical implications. A study by McManimen et al. showed that the diagnosis of CFS/ME was associated with an increased risk of early cardiovascular mortality among patients diagnosed with CFS/ME, with a mean age of 59 years vs. 78 years for the general population in the US [24]. Individuals with CFS/ME may require closer monitoring for the development of CVD, especially those with existing risk factors such as hypertension or hyperlipidemia. Additionally, addressing underlying inflammation or autonomic dysfunction in CFS/ME may help reduce the risk of developing CVD.
Given the dynamic nature of evidence surrounding the relationship between CFS/ME and CVD, the association between CFS/ME and CVD was examined with data from the National Health Interview Survey. However, further research is needed to fully understand the relationship between CFS/ME and CVD and determine the potential clinical implications for individuals with CFS/ME.