Socioeconomic inequalities in allostatic load in a large Norwegian cohort study: the NCDNOR project

Allostatic load (AL) is the physiological burden of stress, and it is suggested to be a mediator between socioeconomic position and health. The aim of this article was to study life-course trajectories in levels of AL by employing data collected over three decades (1994-2019) to compare sex and socioeconomic groups in the adult Norwegian population.

Harmonised data from the following Norwegian health studies were used: the Trøndelag Health Study, the Tromsø Study, the Age 40 Program and CONOR. In total, 264 824 participants aged 30-79 years contributed with 346 312 health examinations. A combined AL score was calculated as the number of biomarkers in the worst quartile among the following eight variables: systolic blood pressure, diastolic blood pressure, resting heart rate, triglycerides, total cholesterol, high-density lipoprotein cholesterol, body mass index and waist-hip ratio. High-sensitivity C reactive protein and glycated haemoglobin were included in sensitivity analyses for a subset of participants. Life-course trajectories were analysed by using a linear mixed model. A shared-parameter model was employed to evaluate attrition caused by death.

Participants with primary education had higher AL compared with secondary and tertiary educated people in all age groups. Men had higher AL than women throughout the life-course. Overall, AL increased with age but levelled off at higher ages among women and decreased at higher ages among men.

We found significant socioeconomic inequalities and sex differences in AL throughout the life-course. This highlights a potential for improvement in public health by effective treatment and public health measures to reduce AL inequities.