Gender- and age-related differences of statin use on incident dementia in patients with rheumatoid arthritis: a Nationwide population-based cohort study

BACKGROUND: Some observational studies have found a significant association between the use of statin and a reduced risk of dementia. However, the results of these studies are unclear in patients with rheumatoid arthritis (RA). This study is to determine the association between the use of statins and the incidence of dementia according to sex and age-related differences in patients with RA. METHODS: We conducted a nationwide retrospective cohort study using the Taiwan Health Insurance Review and Assessment Service database (2003-2016). The primary outcome assessed was the risk of dementia by estimating hazard ratios (HRs) and 95% confidence intervals (CIs). Multiple Cox regression was used to estimate the adjusted hazard ratio of new-onset dementia. Subgroup analysis was also conducted. RESULTS: Among the 264,036 eligible patients with RA aged > 40 years, statin users were compared with non-statin users by propensity score matching at a ratio of 1:1 (25,764 in each group). However, no association was found between the use of statins and the risk of new-onset dementia (NOD) in patients with RA (HR: 1.01; 95% CI: 0.97-1.06). The subgroup analysis identified the use of statin as having a protective effect against developing NOD in male and older patients. CONCLUSION: No association was observed between the use of a statin and the risk of NOD in patients with RA, including patients of both genders and aged 40-60 years, but these parameters were affected by gender and age. The decreased risk of NOD in patients with RA was greater among older male patients. Use of a statin in older male (> 60 years) patients with RA may be needed in clinical practice to prevent dementia.