What Role Does Loneliness Play in Diabetes Risk?

Our individual and collective COVID experiences, now about 2 years old and counting, will undoubtedly register as one of those global events that transformed lives and outlooks. My grandparents talked about the Depression, my parents World War II, and contemporary physicians and most contemporary Americans probably will convey memories of 9/11 and COVID to our descendants.

Each of these milestones has its share of beneficial offshoots: from more stable economic systems, to the creation of international agencies to avert atrocities, to tackling some of the health problems that our COVID experience exposed. We really did incorporate clinically valid telehealth; we really do need to be more assertive in minimizing social health inequities. But keeping our distance from each other with more tenacity than before also exposed some of the adverse health outcomes related to social isolation and loneliness. These had been identified before the pandemic, but as we curtail our face-to-face time and proximity to each other, loneliness has gained more attention as a social determinant of health that is associated with adverse outcomes.

Although defining who is or is not lonely with an objectivity that spans time has impeded the analysis of its effects on health, one monumental survey, the Harvard Study of Adult Development, has amassed an immense amount of data since its start in 1938. A group of students and a group of "core-city" youth were recruited and followed, with contact every 2 years and physical assessment every 5 years. In 2001, the surviving participants, then in their 70s and 80s, were assessed to see where life had taken them health-wise.

The investigators categorized the likelihood of longevity to that age as factors not under the person's control, such as family history or illnesses at age 50 years that limited further longevity, and those that were under their control earlier in life, such as staying mentally challenged at work or not smoking. The best outcomes correlated with stability of social relationships — primarily marriage, but also networks of extended family and friends that people can count on as their own coping abilities falter.

Though much of the literature on loneliness and health outcome originates in psychiatry and social science bibliographies, there are some medical assessments from the United States and China. Though each study showed loneliness as a variable with an independent correlation to mortality over 6 years, the studies also grappled with confounders that intersected with self-reported loneliness. In particular, people in their senior years with established health limitations had physical impediments to engaging with other people outside of their homes. Adjusting for previously established health-related disability greatly attenuated the effect of loneliness as an independent contributor. Moreover, the editorial that accompanied the US study tried to separate measurable social support provided externally, and not always voluntarily, from the subjective assessment of feeling lonely.

These studies were published before the pandemic. Thus, the impact of the pandemic on loneliness and therefore health is further confounded by younger, healthier individuals, noting a greater change from full social engagement to forced restrictions in their schools, workplaces, and recreational outlets. On the other hand, as the Harvard longitudinal survey suggests, investment in social stability at a younger age that persists over decades has its payoffs at older ages. So it may be decades before the impact of our curtailed activities translates into health outcomes.

What About the Impact on Endocrine Disorders?

Amid these limitations, a few studies of the impact of loneliness on endocrine disorders are starting to appear. A study from two military hospitals in Saudi Arabia identified a cohort of patients with treated hypothyroidism. The researchers administered a validated standard survey to assess the severity of loneliness. They found a correlation between duration of hypothyroidism and loneliness score. The prevalence of loneliness among their group of 231 levothyroxine users was 16%. The sample was small relative to the larger US and Chinese studies so it could not capture some of the widely accepted correlations with age and smoking. This study did not separate causes of hypothyroidism into autoimmune and postsurgical groups, nor did it distinguish between undertreated disease and therapeutic replacement therapy, so much remains to be explored.

An extensive 2015 review of chronic medical conditions and loneliness found only a single study examining the contribution of loneliness to diabetes risk but found considerably more linking loneliness to metabolic syndrome. Although progression from metabolic syndrome to diabetes is well established, the extent to which it takes place among those with preexisting loneliness remains inconclusive. One study, published in 2020, includes data from the ongoing English Longitudinal Study of Ageing. This study has been collecting loneliness data since 2004 and reassesses participants every 2 years. This study also distinguishes between social isolation, measured by living arrangements, and the subjective symptom of loneliness, assessed by a standardized, validated questionnaire. Participants who did not have diabetes in 2006, either by personal statement or by elevated A1c, were followed for onset of diabetes over the next 10 years. At the end of the time period, about 6.4% of the 4112 participants had acquired diabetes. Compared with those who remained euglycemic, participants who developed diabetes had greater risks for preexisting depression, higher body mass index, hypertension, and risks for financial constraints. Loneliness scores also offered a statistically significant risk, though scores for social isolation, as they defined it, did not.

Our COVID experience has exaggerated preexisting challenges and created its share of new ones. Those of us with large numbers of geriatric patients in our practices know full well that for many, visits to the doctor break up tedium. For some, it is their most reliable social connection. Telemedicine has its medical advantages but from the experience of the persons who only go out to see the doctor, they miss out on their sole connection to life's pageant — riding in the bus, signing in with the entrance guard, chatting with the receptionist, bantering with others in the waiting area, and laughing together while they watch Jerry Springer's guests assault each other on the waiting room's flat screen.

In the exam room, they feel our fingers palpate their anterior neck and smile when the tuning fork stimulates their malleoli. This all disappears with telemedicine. Loneliness is here to stay. And although it contributes less to heart disease and mortality than the classic risk factors, it also appears to be inadequately studied in the medical literature and as we or our staff question our patients. Of the social determinants that affect the health outcomes we do our best to improve, this may be among the most remediable.

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