Trajectories of pain and cognitive function: 22 years of evidence in mid-to-later life.

Chronic pain has been identified as a risk factor for cognitive decline in later life. However, most studies measure pain at a single time point, and none have investigated whether variations in pain severity are associated with changes in cognitive function over time. This project aimed to assess the relationship between individual-level change in pain severity and decline in cognitive function over time. We used data from the English Longitudinal Study of Ageing, a cohort of nationally representative middle aged and older adults. Pain severity was measured at each wave using a 4-point scale (none, mild, moderate, and severe), and cognitive function was assessed using 3 objective tests. We applied latent growth curve modelling, a method for longitudinal analysis, to 19,376 study participants' data collected over 11 waves, spanning more than 20 years, to examine the relationship between initial level and change of both pain and cognitive function. Adjusting for age and sex, worsening chronic pain severity was associated with accelerated decline in a general measure of cognitive function (β = -0.053, P = 0.039). However, when additionally adjusting for ethnicity, socioeconomic status, and comorbid chronic conditions, this association was attenuated to nonsignificance (β = -0.025, P = 0.365). Greater initial pain severity was associated with steeper decline in cognitive function even in the fully adjusted model (β = -0.104, P < 0.001). Our study suggests that baseline level of pain severity but not worsening pain severity is associated with steeper decline in cognitive function over time.