Colorectal cancer (CRC) is the second most common cause of cancer-related deaths in the world, accounting for over 953,173 deaths in 2020. The incidence of this neoplasm is also the third highest after breast and lung cancer irrespective of gender, with an estimated 1,931,590 new cases in 2020. Five-year relative survival rate for patients with CRC in Spain is just 57%. Survival of CRC patients detected in a screening program is higher than that of patients diagnosed for symptoms.1 The screening strategy for average risk population (individuals between 50 and 70 years old without additional risk factors) is a biennial Fecal Occult Blood Test (FOBT), sigmoidoscopy every 3–5 years or colonoscopy every 10 years.2 Although coverage of the screening programs is nearly universal in Spain, participation in such programs is still below 50% and most CRCs are still being diagnosed outside of the screening programs. There are three groups of factors associated with adherence to population screening: those related to the organization of the screening program, those dependent on the views of the individual3 and those related to social and familial factors. In this article, we will focus on these last constraints.

There are many social factors that influence adherence to screening and many of them, such as income level, race or ethnicity, geographical factors, gender, level of education and the degree of knowledge about CRC,4 are well assessed in the literature. There are, however, two social and familial factors whose relationship with CRC screening is less thoroughly studied, such as social support (SS) and stressful life events (SLE).

SS may be defined as an interactive process through which individuals obtain emotional, instrumental or financial aid from the social network in which they are involved.5, 6 SLE would be those events requiring a degree of adjustment to the daily activities of the individuals, who perceive such adjustments as undesirable.7 Prevalence of low social support is estimated between 20 and 35% in the general population. This percentage is higher for individuals with chronic pathologies living in disadvantaged areas, with figures of low social support of up to 65%. The influence of SS on the mortality risk has been shown to be comparable with well-established risk factors. Patients with chronic conditions such as high blood pressure or diabetes and lower social support are at a higher risk of developing cardiovascular events and dying during long-term follow-up.8 In population studies, social isolation has been associated with higher mortality, accident and suicide rates; likewise, recent studies show the influence of SS on mortality due to heart failure or cancer.9 On the other hand, the influence of SLE on high blood pressure, physical and psychological problems or the chance of suffering a cerebrovascular accident for patients with high blood pressure has been demonstrated, with a prevalence of about 50%.10 Due to their knowledge about the patient and his or her environment, Primary Care professionals play an important role in the detection of the SLE referred by the individuals along their lifes, as well as those cases with lower SS.

There is scarce evidence about the impact of the SS and SLE on the adherence to a CRC screening program. Two systematic reviews11, 12 showed the importance of the perceived family support and the social network, as well as the marital status. Moreover, two meta-analysis and two systematic reviews of interventional studies showed that peer support, partner's support and a cohesive health team increase the participation in the screening.13, 14, 15, 16 These interventions are more efficient if the barriers to the screening program are reduced, if an education “one to one” strategy is conducted and if they are implemented in a community level. Finally, although there is no evidence about the effect of the SLE on the adherence to the screening programs, two epidemiologic studies suggest an association between SLE and the risk of CRC detection.17, 18

This study aims to ascertain the influence of social support and stressful life events on the adherence to the population screening of CRC with FOBT in Spanish average risk population.