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Mental health and the risk of developing diabetes may be linked. mrs/Getty Images
  • A new, 20-year follow-up study found that individuals who feel lonely face a higher risk of developing type 2 diabetes.
  • Of all the participants, 1,179, or 4.9%, developed type 2 diabetes over the course of the study.
  • About 13% of the participants reported experiencing loneliness.
  • The individuals who felt the most lonely had a two-fold higher risk of developing type 2 diabetes than those who did not feel lonely.

Researchers from Western Norway University of Applied Sciences have found that feelings of loneliness are linked to a significantly higher risk of developing type 2 diabetes.

The 20-year follow-up study, published in Diabetologia, the journal of the European Association for the Study of Diabetes [EASD], used data from the Trøndelag Health Study (the HUNT study), a large longitudinal health study based on a population from central Norway.

Roger E. Henriksen, associate professor at the Institute of Nursing at Western Norway University of Applied Sciences, became interested in how social relationships impact physical health about a decade ago after hearing James A. Coan, director of the Virginia Affective Neuroscience Laboratory at the University of Virginia, speak about social baseline theory. The theory surmises that the human brain expects access to social relationships that mitigate risk and lower the level of effort needed to meet goals.

“At a neurological level, it means the brain actually expects to be together with people you trust,” Henriksen explained to Medical News Today.

In 2014, Henriksen co-authored a study that asked whether an individual who lacks significant relationships “may experience more demands on their own neural metabolic resources on a daily basis when solving problems, remaining vigilant against potential threats and regulating emotional responses.” That study concluded that relative social isolation leads to increased levels of sugar intake.

Other studies, including one from 2017, have concluded stress is a risk factor for type 2 diabetes.

Henriksen wanted to see whether the increased levels of sugar intake by people who lack social relationships translated to those individuals facing a higher rate of developing type 2 diabetes.

Since the HUNT study was launched in 1984, more than 230,000 participants have provided health information on questionnaires, underwent health exams, and provided blood samples for research.

For this study, the Norwegian researchers used data from three of the HUNT study’s population surveys. HUNT2 included research undertaken between 1995-1997, HUNT3 encompassed research undertaken between 2006-2008, and HUNT4 comprised research undertaken between 2017-2019.

Henriksen and the study’s co-authors excluded participants who had type 1 and type 2 diabetes and those who had metabolic disorders between 1995 and 1997. Other participants were excluded due to missing data.

Ultimately, more than 24,000 participants were used in the study’s analyses.

The researchers looked at the results of HUNT2 to see how participants answered the question: “In the last two weeks, have you felt lonely?” Participants could respond “no,” “a little,” “a good amount,” and “very much.”

Researchers looked at the blood samples of participants from HUNT4 to see who had developed type 2 diabetes over the 20-year period.

Additionally, researchers looked at the results from HUNT3 where participants answered the Hospital Anxiety and Depression Scale as well as a sleep questionnaire. Analyses were adjusted for socioeconomic factors, age, sex, and education.

Among 24,024 participants, 1,179, or 4.9%, developed type 2 diabetes between 1995 and 1997 and 2017 and 2019.

The participants who developed type 2 diabetes were more likely to be male (59% vs. 41%), had a higher mean age (48 years vs. 43 years), were more likely to be married (73% vs. 68%), and have the lowest level of education (35% vs. 23%) than those without type 2 diabetes.

Among the participants, 12.6% reported feeling varying degrees of being lonely.

Participants who answered “very much” when asked if they’d experienced loneliness in the last two weeks in the HUNT2 survey had two times higher odds of having type 2 diabetes in the HUNT4 survey as compared to those who reported not feeling lonely.

“The finding is important because [type 2 diabetes] is a disease that affects many people,” Henriksen told MNT. “The [World Health Organization] has recently listed [type 2 diabetes] among the top 10 causes of death worldwide. Identifying a risk factor for such a widespread disease is always important.”

The researchers of the study theorize in their paper that loneliness may activate the body’s physiological stress response which leads to changes in the body’s cardiovascular system and production of cortisol, a steroid hormone produced by the adrenal glands—also known as the stress hormone. In their paper, the researchers write:

“This, in turn, may lead to increased food intake, in particular the intake of carbohydrates, and to increased insulin resistance. These processes play an important role in supplying the activated, metabolically demanding brain with sufficient glucose.”

Additionally, the researchers speculate that social support may influence an individual to maintain a healthier lifestyle with exercise and a healthy diet.

Andrea Paul, a physician and a medical advisor for Illuminate Labs, stressed to MNT that the study shows loneliness is associated with a higher risk of developing type 2 diabetes but doesn’t show a causative link.

“It’s more likely, in my opinion, that people who are extremely lonely also overlap with people [who] don’t focus as much on health,” she explained.

“It’s uncommon to come across someone who’s very lonely but also focused on nutrition, exercise, and wellness. While loneliness may directly cause diabetes by activation of stress hormones, this study doesn’t prove so,” she added.

For this study, the researchers also looked at whether depression on insomnia plays a role in participants developing type 2 diabetes.

“Previous research has shown us that loneliness can lead to depression. And loneliness can also lead to bad sleep. And we also know that bad sleep and depression can lead to type 2 diabetes,” Herniksen said.

“[T]here is a reason to believe that maybe if we find this link between loneliness and type 2 diabetes, it could be explained by sleep and depression. Maybe that’s the mechanism.”
— Roger E. Henriksen

In the end, however, the researchers’ analyses showed that neither depression, sleep-onset insomnia (difficulty falling asleep), nor terminal insomnia (waking too early) mediates the association between loneliness and type 2 diabetes. The team did find a weak mediating effect of sleep maintenance insomnia (difficulty staying asleep).

“It was like almost nothing,” Henriksen told MNT of that finding.

Still, Henriksen would like to see other researchers examine the relationship between loneliness and type 2 diabetes and whether it’s affected by the presence of depression or different types of insomnia.

“I still think we should investigate this. I can’t understand that depression or sleep should not play a role,” he said.

Henriksen next hopes to look at which interventions are successful at making individuals feel less lonely. Working with Norway’s Red Cross, Henriksen plans to study the impact of designing individually tailored approaches for lonely patients.

“It’s more like talking to [patients] one on one and trying to find out who will be a good match with each other and stuff like that,” he told MNT.