LONDON -- For some patients with cardiovascular disease risk factors, the root cause may be the loneliness of childhood, according to a study that followed more than 1,000 adults from birth.
LONDON, Aug. 7 -- For some patients with cardiovascular disease risk factors, the root cause may be the loneliness of childhood, according to a study that followed more than 1,000 adults from birth.
Those who were socially isolated as children and adolescents were up to 2.5 times more likely than others to have three or more risk factors for cardiovascular disease, including hypertension and elevated cholesterol, said Avshalom Caspi, Ph.D., of the Institute of Psychiatry here.
The finding wasn't explained by health-damaging behaviors, such as drinking and smoking, that might expected from lonely persons, Dr. Caspi and colleagues reported in the August issue of Archives of Pediatrics & Adolescent Medicine.
"The findings from this study provide, to our knowledge, the first evidence linking childhood social isolation to poor adult health," the authors said. In fact, several of the study's findings suggest a causal connection rather than a mere association, they added.
The study followed 1,037 New Zealanders from birth through age 26. Members of this longitudinal birth cohort underwent social and health assessments at regular yearly intervals. Information on social isolation was gathered from parents and teachers as well.
The main outcome was elevated risk for cardiovascular disease, as determined by the presence of three or more of the following risk factors: overweight, high blood pressure, high total cholesterol, low HDL levels, elevated glycated hemoglobin, and low maximum oxygen consumption.
For every standard-deviation increase of loneliness in childhood, the adults at age 26 were 37% more likely to have higher disease risk (relative risk=1.37; 95% confidence interval=1.17 to 1.61).
The results remained nearly unchanged after controlling for known childhood risk factors for cardiovascular disease later in life, such as overweight, low socioeconomic status, and low IQ.
Nor could the explanation be found in the hypothesis that lonely individuals tended to engage more often in unhealthy behavior such as smoking and abusing alcohol or avoiding exercise. The result remained significant after controlling for these behaviors, the investigators said.
They also ruled out the explanation that lonely children grow up to be exposed to more stress later in life. The results remained virtually unchanged after adjusting for life stressors common to adults who were lonely as children, such as low status attainment and depression, they said.
Lonely children were at increased risk for becoming lonely adults (RR=1.37; 95% CI=1.13 to 1.66), and so were lonely adolescents (RR=1.61; 95% CI=1.30 to 1.99).
Furthermore, the link between loneliness and cardiovascular disease risk followed a dose-response relationship, with those who had been isolated both in childhood and adolescence more than doubling their risk (RR=2.58; 95% CI=1.46 to 4.56).
Loneliness may be a form of chronic stress that activates the sympathetic nervous and hypothalamic-pituitary-adrenocortical systems and induces pathophysiologic responses that raise the risk for cardiovascular disease, the investigators speculated.
"It is also possible that social isolation disrupts constructive and restorative processes that enhance physiological capacities, as suggested by evidence that lonely individuals experience disrupted sleep and engage in passive rather than active coping strategies in their everyday lives," they said.
"The findings appear to meet several criteria suggestive of a causal association between social isolation and adult health," they said, including:
A chief limitation of the study, however, was the relative youth of the cohort. Because the members were so young, the investigators could not analyze the outcome of actual cardiovascular disease, which tends to show itself in mid-life or old age, they said.
Nevertheless, "The findings underscore the usefulness of a life-course approach to health research, by focusing attention on the effect of the timing of psychosocial risk factors in relation to adult health," the authors concluded.