Abstract
Depressive disorders are a leading cause of disability in older age. Although the role of psychosocial and behavioural predictors has been well examined, little is known about the biological origins of depression. Findings from animal studies have implicated insulin-like growth factor 1 (IGF-1) in the aetiology of this disorder. A total of 6017 older adults (mean age of 65.7 years; 55% women) from the English Longitudinal Study of Ageing provided serum levels of IGF-1 (mean=15.9 nmol l−1, s.d. 5.7) during a nurse visit in 2008. Depression symptoms were assessed in the same year and again in 2012 using the eight-item Center for Epidemiologic Studies Depression Scale. Self-reports of a physician-diagnosis of depression were also collected at both time points. In separate analyses for men and women, the results from both the cross-sectional and longitudinal analyses revealed a ‘U'-shaped pattern of association, such that lower and higher levels of IGF-1 were associated with a slightly elevated risk of depression, whereas the lowest risk was seen around the median levels. Thus, in men, with the lowest quintile of IGF-1 as the referent, the age-adjusted odds ratios (95% confidence interval) of developing depression symptoms after 4 years of follow-up, for increasing quintiles of IGF-1, were: 0.51 (0.28–0.91), 0.50 (0.27–0.92), 0.63 (0.35–1.15) and 0.63 (0.35–1.13) (P-value for quadratic association 0.002). Some attenuation of these effects was apparent after adjustment for co-morbidity, socioeconomic status and health behaviours. In conclusion, in the present study of older adults, there was some evidence that moderate levels of IGF-1 levels conferred a reduced risk of depression.
Highlights
Depression, a major public health problem, has profound effects on the economy and on individuals
Insulin-like growth factor 1 (IGF-1) is a complex peptide hormone produced in multiple tissue sites whose main function is to mediate cell growth, differentiation and transformation by promoting mitosis and inhibiting apoptosis
IGF-1 and baseline characteristics: cross-sectional analyses In Table 1 and Table 2, we present baseline study participant characteristics according to IGF-1 quintiles
Summary
Depression, a major public health problem, has profound effects on the economy and on individuals. According to the World Health Organization, it is the leading cause of disability worldwide, responsible for 65 million disability-adjusted life years in 2008.2 In addition to being an important disease in its own right, depression is associated with an increased risk of suicide, cardiovascular disease, some cancers and premature mortality.. Effective treatments for depression are available, the majority of cases among older people remain undiagnosed; prevention of the disorder is crucial.. Insulin-like growth factor 1 (IGF-1) is a complex peptide hormone produced in multiple tissue sites whose main function is to mediate cell growth, differentiation and transformation by promoting mitosis and inhibiting apoptosis.. Evidence from laboratory studies suggests that expression and function of IGF-1 is similar in humans and rodents.. According to the World Health Organization, it is the leading cause of disability worldwide, responsible for 65 million disability-adjusted life years in 2008.2 In addition to being an important disease in its own right, depression is associated with an increased risk of suicide, cardiovascular disease, some cancers and premature mortality. effective treatments for depression are available, the majority of cases among older people remain undiagnosed; prevention of the disorder is crucial. A series of studies have identified a range of behavioural (heavy alcohol use, some dietary characteristics) and social (loneliness, socioeconomic disadvantage, bereavement) predictors of depression in later life. the aetiological role of weight, height, genetic factors and several plasma markers has been examined, relatively less attention has been paid to biological risk factors.
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