Socioeconomic variation in modifiable risk factors for dementia

Abstract

AbstractBackgroundMost studies on modifiable risk factors for dementia are in relatively affluent populations, but dementia risk is higher among those who are more materially deprived. We aimed to consider whether this is accounted for by potentially modifiable risk factors, and compare the overall population attributable fraction (PAF) in the least and most socioeconomically deprived participants within the UK Biobank (UKB).MethodThe UKB is a cohort study with 502,656 volunteer participants registered between 2006‐2010, aged 40‐60 years at baseline, and followed for up to 16.8 years. Material deprivation was quantified using the Townsend Deprivation Index grouped into quintiles, with higher scores meaning higher deprivation. We assessed interactions between Townsend quintiles (using least deprived as reference), and each modifiable risk factor. To estimate the PAFs of 12 modifiable risk factors (diabetes, hypertension, depression, hearing loss, obesity, traumatic brain injury, less education, social isolation, physical inactivity, air pollution, and smoking), we first estimated hazard ratios (HRs) (adjusted for age, gender, and ethnicity) stratified by Townsend. HRs were then converted to relative risk for PAF calculation.Results6,624 incident cases of dementia developed in 1.6%(95%CI = 1.5‐1.7)(n = 11679/10369) of participants in the most deprived group, compared to 1.2%(95%CI = 1.1‐1.3)(n = 1174/98074) in the least deprived group. The mean age at dementia diagnosis were 72.7 years(SD,6.3){in most deprived}, and 73.8 years(SD,5.1){in least deprived}. The combined PAF(95%CI) for dementia was 40.3%(40.0‐40.6){most deprived}, versus 27.2%(27.0‐27.5){least deprived}. The most deprived, compared to the least deprived, had higher PAFs for: (a)Midlife hypertension: 7.7%(7.6‐7.9) vs 4.1%(3.9‐4.2); (b)Less education: 5.8%(5.6‐5.9) vs 3.4%(3.2‐3.6); (c)Diabetes: 4.4%(4.3‐4.6) vs 3.1%(3.0‐3.2); (d)Physical inactivity: 3.5%(3.4‐3.6) vs 0.7%(0.6‐0.7);) (e)Social isolation: 3.4%(3.3‐3.5) vs 1.0%(1.0‐1.1); (f)Midlife obesity: 2.1%(2.0‐2.2) vs 1.2%(1.2‐1.3); and (g)Smoking 1.8%(1.7‐1.9) vs 0.5%(0.5‐0.6). Air pollution had a PAF of 1.8%(1.7‐1.9) in the least deprived, and 0.0% in the most deprived. The remaining risk factor PAFs did not differ between the most and least deprived.ConclusionsIn this volunteer cohort, which is relatively wealthy, a higher proportion of dementia cases were attributable to major modifiable risk factors in more socioeconomically disadvantaged participants. Targeted interventions particularly addressing midlife hypertension, education, physical activity and social isolation might mitigate known inequalities in dementia risk according to socioeconomic status.