Socioeconomic Determinants of Inflammation and Neuroendocrine Activity: A Longitudinal Analysis of Compositional and Contextual Effects

Abstract

Socioeconomic determinants are well-established modulators of inflammation and neuroendocrine activity. Less clear is whether neighbourhood-contextual or individual-compositional factors are more closely associated with gradients in these biomarkers. Here, we examine how immune and neuroendocrine activity are cross-sectionally and longitudinally nested in meso-level socioeconomic characteristics. Participants, male and female, aged ≥ 50, were recruited from the English Longitudinal Study of Ageing (ELSA). Neighbourhood (Index of Multiple Deprivation [IMD]) and individual (Wealth/Education/Occupational Social Class [OSC]) factors were drawn from wave 4 (baseline; 2008). Immune and neuroendocrine biomarkers (indexed by C-reactive protein [CRP; n = 3,968]; fibrinogen ([Fb] n = 3,932); white blood cell counts [WBCC; n = 4,022]; insulin-like growth factor-1 [IGF-1; n = 4,056]) were measured at baseline and 4-years later (wave 6; 2012). Covariates at baseline included demographic, clinical, and lifestyle variables. Lower socioeconomic status was associated with heighted inflammation and lower neuroendocrine activity unadjusted both cross-sectionally and longitudinally. With few exceptions, cross-sectional associations remained significant after full adjustment. Prospectively, low IMD remained associated with higher CRP and WBCC; wealth with WBCC; and education and OSC with Fb and WBCC. IMD-biomarker associations were reduced when wealth was simultaneously taken into account. Lifestyle accounted for the greatest variance in associations between socioeconomic indicators and inflammation (≤ 42.11%), but demographics were more salient to neuroendocrine activity (≤ 88.46%). Neighbourhood-contextual factors were stronger indicators of aberrant biomarker activity than individual-compositional factors in cross-sectional analyses but were largely explained by wealth differences prospectively. Therefore, immune and neuroendocrine changes depended on the composition of the population living in an area, rather than the area itself.

Stress and Sleep Duration in Immune and Neuroendocrine Patterning. An Analytical Triangulation in ELSA

“…Future study may benefit from objective measures in a time-varying effect model (Tan et al, 2012). Moreover, financial stress was measured with a single item, so it may not have captured the multidimensionality of material deprivation (Hamilton & Steptoe, 2022). While the causal DAG represented a particular set of assumptions, its complexity does not explicitly reflect real-world concerns about reciprocity or sources of bias, and it does not specify the estimate magnitude, nor its interplay with random errors (Lipsky & Greenland, 2022).…”

“…The most intriguing aspect of inflammation is the plurality of its modulators and its breadth of effects that support health or contribute to morbidity, both physical and mental, and mortality worldwide (Jerison, 2024;Furman et al, 2019). With multilateral, cross-blood-brain-barrier signalling between the immune, nervous, and endocrine systems (Becher et al, 2017), avenues of inquiry have found that abnormal circulating concentrations of pro-inflammatory and endocrinemediated biomarkers have been implicated in the genesis and progression of disease and psychiatric disorder across a spectrum of severity (Furman et al, 2019;Hamilton & Steptoe, 2022;Tomasik et al, 2023;Yuan et al, 2019). A disease burden that not only intimates premature death but suffering as people live with it (Whiteford et al, 2013).…”