Anticoagulant treatment and COVID-19 mortality among older adults living in nursing homes in Sweden.

Background: Anticoagulants (AC) were introduced in March 2020 as standard of care in nursing home (NH) residents affected with COVID-19 in the Stockholm region, Sweden. ACs are proven to reduce the risk of complications and mortality from COVID-19 among patients of other ages and settings, but there is limited scientific evidence underpinning this practice in the NH setting. Methods: This matched cohort study included 182 NH residents in the Stockholm Region diagnosed with COVID-19 in March-May 2020. The main exposure was any AC treatment. Exposed (n = 91), 49% prevalent (pre-COVID-19 diagnosis) AC and 51% incident AC were compared with unexposed controls (n = 91). The outcome was 28-days all-cause mortality after COVID-19 infection. The mortality odds ratios (OR) were assessed using logistic regression, adjusted for age, sex, multimorbidity, and mobility, also stratified by incident or prevalent AC-type, age group, and sex. Results: Of the 182 individuals diagnosed with COVID-19 (median age 88 years, 68% women), 39% died within 28 days after diagnosis. Use of either incident or prevalent AC was associated with a reduced, adjusted 28-day mortality (OR[95% CI]: 0.31[0.16-0.62]). In stratified analyses, the association was significant in both age groups: 70-89 (OR: 0.37 [0.15-0.89]) and 90-99 years of age (OR: 0.22 [0.07-0.65]. In sex-stratified analysis, the AC-lowering effect was significant in women only (OR: 0.28[0.11-0.67]). In the analyses stratified by AC type, the mortality-lowering effect was observed for both prevalent AC (OR: 0.35[0.12-0.99]) and incident AC (OR: 0.29[0.11-0.76]). Conclusions: Both prevalent and incident use of ACs in prophylactic dosing was associated with reduced 28-day mortality among older individuals with COVID-19 in a NH setting. The effect was seen across age-strata and in women. The findings present new insight in best practice for individuals diagnosed with COVID-19 in the NH setting.