Objective

To test the hypothesis that children who occupy peripheral or isolated roles in their peer groups (isolated children) are at risk of poor adult health.

Design

Longitudinal study of an entire birth cohort.

Setting

Dunedin, New Zealand.

Participants

A total of 1037 children who were followed up from birth to age 26 years.

Interventions

Measurement of social isolation in childhood, adolescence, and adulthood.

Main outcome measures

When study members were 26 years old, we measured adult cardiovascular multifactorial risk status (overweight, elevated blood pressure, elevated total cholesterol level, low high-density lipoprotein level, elevated glycated hemoglobin concentration, and low maximum oxygen consumption).

Results

Socially isolated children were at significant risk of poor adult health compared with nonisolated children (risk ratio, 1.37; 95% confidence interval, 1.17-1.61). This association was independent of other well-established childhood risk factors for poor adult health (low childhood socioeconomic status, low childhood IQ, childhood overweight), was not accounted for by health-damaging behaviors (lack of exercise, smoking, alcohol misuse), and was not attributable to greater exposure to stressful life events. In addition, longitudinal findings showed that chronic social isolation across multiple developmental periods had a cumulative, dose-response relationship to poor adult health (risk ratio, 2.58; 95% confidence interval, 1.46-4.56).

Conclusions

Longitudinal findings about children followed up to adulthood suggest that social isolation has persistent and cumulative detrimental effects on adult health. 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.