The present study revealed social isolation in patients with CLTI presenting with ischemic tissue loss and requiring revascularization. The results showed that patients living alone accounted for 24.5% (20.1–28.8%) of the overall population. We also found that patients receiving welfare were more likely to live alone. Among the patients living alone, 21.8% (12.8–30.8%) met a trusted family member or friend in their daily lives less than once per year. Younger age and receiving welfare were independently associated with lower frequency of meeting a trusted family member or friend in the daily lives of the patients. Regarding hospitalization, 9.9% (6.8–13.0%) of the overall population were not visited in the hospital by a trusted family member or friend. Younger age and receiving welfare were again independently associated with lower frequency of hospital visits by a trusted family member or friend. Our findings indicate that a considerable number of patients with CLTI are socially isolated, both in daily life and during hospitalization. To the best of our knowledge, this is the first report on social isolation in patients with CLTI.
The present study revealed that social isolation is common in patients with CLTI. Although social isolation as a concept was established decades ago and has recently started attracting increasing attention, there is no standard, international, widely used, or cross-culturally valid measure of the concept13. The definition of social isolation therefore varied from study to study, which made it difficult to compare the prevalence among studies. Exceptionally, living alone is a marker for social isolation that has been widely adopted. In Japan, the prevalence of living alone was reported to be 9–18% in community-dwelling older adults11,12,13,14 and 15–21% in patients with cardiovascular diseases15,16,17,18,19. The corresponding prevalence in the study population was 24.5% (95% CI 20.1–28.8%), suggesting that the prevalence was at least not lower (or possibly slightly higher) than in other populations. Social isolation is a common issue faced in the clinical management of CLTI.
The present study also showed that receiving welfare was an associated factor, indicating an association between low socioeconomic status and social isolation. Although the causal relationship between these factors remained unproven, our finding is consistent with previous reports20. Individuals with low socioeconomic status are at a disadvantage in shaping their living conditions and physical environments, which provide access and opportunities to develop and maintain social connections20.
Age was also an associated factor. Age was inversely associated with both lower frequency of meeting a trusted family member or friend in the daily life of a patient living alone and lower frequency of hospital visitation by a trusted family member or friend, indicating that younger patients with CLTI were more likely to be socially isolated than older patients. The reason why age was inversely associated with social isolation remained unknown. The present finding is contrary to some previous studies showing that social isolation increases with age20,21. The positive association between age and social isolation in these previous studies was observed in a general population, and was reasonably attributed to the fact that life transitions and disruptive life events (such as retirement; bereavement of a spouse, partner or friends; migration of children; and disability or loss of mobility) are more likely to affect older people20,21,22,23,24. In contrast, the present study analyzed a population with CLTI. Social isolation is a risk factor for various diseases including peripheral artery disease25,26, indicating that socially isolated patients will likely develop the disease earlier (i.e., at younger age). Although the association between social isolation and CLTI remained unrevealed, socially isolated patients might develop CLTI similarly earlier. When one focuses on a population with CLTI, patients in whom social isolation contributed to their CLTI development might be more commonly seen in a younger subgroup. That might be why the prevalence of social isolation was inversely associated with age in this population. Indeed, some studies reported a similarly inverse association between social isolation and age in a population with a disease for which social isolation is known as a risk factor27,28. The finding that the association in a diseased population was opposite to that observed in a general population might be warranted, although the true mechanism remained unknown.
There was no significant association between social isolation and visual impairment, loss of pressure sensation, or non-ambulatory status in the present study. This indicates that vulnerable patients, who are expected to require ample support from others for foot care and daily living, are as commonly socially isolated as non-vulnerable patients. Furthermore, diabetes mellitus and other cardiovascular risk factors were not associated with social isolation; in other words, these comorbidities were as prevalent in socially isolated patients as in patients with healthy social relationships. Social isolation increases the risk of poorer diet, lower physical activity, and poor adherence to medical treatments22, which can considerably interfere with the control of those comorbidities in the CLTI population. As recommended in clinical guidelines, patients with CLTI require appropriate control of diabetes mellitus and other cardiovascular risk factors, as well as healthy diet, exercise, and preventive foot care2. Social isolation is a clinical issue that cannot be ignored in the management of patients with CLTI.
One major limitation of the present study was that the association between social isolation and clinical outcomes was not analyzed. Currently, data on clinical outcomes are not available in this registry. Recent studies have demonstrated that social isolation has negative effects on health, prognosis, and well-being in various populations22,29,30,31,32,33,34,35, plausibly due to poor diet, low physical activity, poor adherence to medical treatments, and reduced psychological stress-buffering effect of social support22. It has also been reported that social isolation increases resource utilization and costs36. Future studies are needed to reveal the association between social isolation and clinical outcomes in this population.
The present study has several other limitations. First, although social isolation as a concept was established decades ago and has recently started attracting increasing attention, there is no standard, international, widely used, or cross-culturally valid measure of the concept22. Social isolation denotes the objective state of having a reduced network of kin and non-kin relationships and thus, few or infrequent interactions with others22. We tentatively measured social isolation using residence status and the involvement of a trusted family member or friend in a patient’s life. However, these measurements are not yet externally validated. Furthermore, we categorized the frequency of visits by a trusted family member or friend into five categories, not according to any evidence or established classification system, but simply on our empirical basis. The categorization was prespecified in our registry, and the relevant data were accordingly collected. We were therefore unable to analyze the relevant data according to a different categorization or definition. Second, our database did not include a general population or a population with other atherosclerotic diseases. We were therefore unable to compare the prevalence of social isolation between the CLTI population and other populations. Third, the data on treatment before the index referral, including primary foot care and patient education, were unavailable in this study. In addition, the reason for living alone or the reason for lower frequency of daily contact and hospital visits by a trusted family member or friend of a patient are unknown. Fourth, we included patients with CLTI scheduled for infrapopliteal revascularization. Although most patients with CLTI undergo infrapopliteal revascularization in clinical settings37,38,39, whether the findings of this study would be applicable for patients undergoing revascularization of other vascular territories is unknown. Furthermore, this study was conducted in Japan. Other countries, with different healthcare systems and societal structures, would have different trends in social isolation. Thus, future studies conducted in other countries are warranted.