September 17, 2025, 2:01 pm | Read time: 5 minutes
Loneliness is particularly widespread among older people and is associated with health consequences. A study now shows that especially lonely children have a higher risk of developing dementia many years later. FITBOOK author Martin Lewicki presents the findings and spoke with study author Prof. Xiuhua Guo.
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How did the researchers conduct the study?
A large-scale study from 2022 already showed that loneliness in people over 50 changes brain structure and thus contributes to the development of dementia (FITBOOK reported). However, it is evident that a lonely childhood is already a crucial factor for dementia risk in later life, as Chinese researchers now demonstrate in a recent study.1 The analysis of data from 13,592 study participants showed the following: The risk of dementia increases by 41 percent if one had no close friendships in childhood. This childhood deficit apparently cannot be compensated for later, even if one maintains friendships as an adult. But why is that?
To determine the influence of a lonely childhood on dementia risk, Chinese researchers used data from the “China Health and Retirement Longitudinal Study” (CHARLS). This is a long-term study in which 13,592 people aged 45 and older were observed and interviewed between 2011 and 2018. Only data before the COVID-19 pandemic were considered to avoid distortions from later isolation.
To assess childhood loneliness, two key questions were asked of the study participants:
- “How often did you feel lonely as a child because you had no friends? Was it often, sometimes, not very often, or never?”
- “Did you have a close friend as a child?”
Participants who reported often feeling lonely and having no close friend before the age of 17 were defined as affected by childhood loneliness. Those who met only one criterion were considered possibly affected; those who met neither were considered not affected by childhood loneliness.
Loneliness in adulthood, on the other hand, was assessed using a single question from the 10-point scale of the “Center for Epidemiological Studies Depression Scale”:
- “How often have you felt lonely in the past week?”
These are the connections between childhood loneliness and dementia risk
The data analysis revealed that about half of the respondents (52 percent of women and 48 percent of men) were affected by “possible childhood loneliness.” 565 people, or about 4.2 percent, clearly stated that they had been lonely during their childhood and adolescence. Nearly every second study participant reported not having close friendships during that time.
Regarding individual points, 883 participants (6.5 percent) reported often feeling lonely, and 6,772 participants (49.8 percent) reported having no close friends during their childhood. Compared to participants without childhood loneliness, those who experienced loneliness in childhood were older and more likely to have lived in rural areas during their childhood. They also had a lower educational level and a lower socioeconomic status. At the same time, they showed a higher rate of loneliness in adulthood and poorer cognitive performance.
The seven-year observation period showed: Lonely children have a higher risk of dementia in later life. A total of 697 new cases of dementia occurred during the observation period, which corresponds to about five percent of the study participants. The most important finding: The dementia rate was significantly higher among people who suffered from childhood loneliness. They had a 41 percent higher risk of dementia compared to those who were not lonely in their childhood. The group of people who reported only not having close friends, however, did not show a noticeable rate.
Study author Prof. Xiuhua Guo tells FITBOOK that loneliness is not the strongest but an important independent risk factor. In addition, there are other factors, such as lower educational attainment and socioeconomic status.
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What future research should consider according to Xiuhua Guo
“Future work should prioritize prospective cohorts from childhood to avoid recall bias (errors due to poor memory, ed. note) and expand replication to populations with different sociocultural and genetic backgrounds. Prospective intervention studies to reduce childhood loneliness could help more conclusively demonstrate causality.”
Childhood loneliness cannot be compensated for later
Even people who were only lonely as children but not as adults still had a higher risk of dementia. And apparently, loneliness in older age does not have as strong an impact on dementia risk as in childhood. The data also showed that loneliness in adulthood only increases the risk of cognitive decline by about nine percent and the risk of dementia by 17 percent.
Thus, it becomes clear that the particularly formative phase of childhood, during which crucial brain structures develop, influences cognitive performance in old age. The Chinese researchers therefore recommend taking measures to prevent loneliness early in childhood. This way, children can not only experience a more enjoyable childhood but also significantly reduce their risk of dementia in old age.
The importance of the topic is also highlighted by a recent study by the German Youth Institute (DJI).2 In the study “Growing Up in Germany: Everyday Worlds” (AID:A), 17 percent of 5- to 11-year-olds reported in 2023 that they sometimes feel alone, and five percent said they feel this way often or even constantly. According to the study’s analysis, 22 percent of elementary school-aged children feel lonely at least sometimes. This corresponds to more than one in five children.