Characteristics of study cohort on care home entry
Between 2003 and 2018, 14 493 people with AF aged ≥65 years who had ≥12 months of primary care data became new residents in care homes in Wales (Table 1 and Supplementary Figure S1). The median age of the cohort was 87.0 years (interquartile range [IQR] 82.6–91.2) and 5103 (35.2%) were male.
Table 1. Characteristics of adults with atrial fibrillation aged ≥65 years on care home entry (2003–2018) within the SAIL Databank, by prescription of oral anticoagulation
Of the total cohort with AF, 7057 (48.7%) had a record of OAC prescription within 6 months before care home entry (Table 1). There were 5734 (81.3%) residents on vitamin K antagonist (VKA), 623 (8.8%) on NOACs, and 700 (9.9%) that switched between VKA or NOAC therapy in the 6 months preceding care home entry (data not shown).
The proportion of residents prescribed OACs increased from 32.7% in 2003 to 72.7% in 2018 (Figure 1). In 2003, all residents were on VKA. In 2018, 385 (33.0%) were on VKA, 228 (19.5%) were on NOACs, and 236 (20.2%) changed between VKA or NOACs before care home entry (data not shown).
Figure 1. Proportion of care home residents aged ≥65 years with atrial fibrillation prescribed an oral anticoagulant within 6 months before care home entry between 2003 and 2018.
EMA = European Medicines Agency. NOAC = non- vitamin K antagonist oral anticoagulant.
Residents prescribed OACs were slightly younger (median age 86.2 years, IQR 81.9– 90.2 versus 87.9 years, IQR 83.4– 92.0) and a higher proportion were male (37.9% versus 32.6%). The median stroke risk (CHA2DS2-VASc score 4, IQR 3–5) at care home entry was the same in residents prescribed OACs and those residents not prescribed OACs, with a slightly higher median bleeding risk at care home entry for those prescribed OACs (HAS-BLED score 3, IQR 2–3 versus 2, IQR 2–3, respectively) (Table 1).
There was a greater proportion of residents not prescribed OACs on care home entry who were classified as non- frail (21.5% versus 3.7%), whereas more residents categorised with moderate (39.9% versus 31.3%) or severe frailty (34.1% versus 18.4%) were prescribed OACs (Table 1). Severely frail residents more commonly had a history of stroke, transient ischaemic attack (TIA), myocardial infarction, hypertension, heart failure (HF), peripheral vascular disease (PVD), venous thromboembolism (VTE), and diabetes compared with those who were mildly or moderately frail. This translated into a higher median CHA2DS2- VASc score of 5 (IQR 4–5) for severely frail residents compared with 4 (IQR 3–5) for mild or moderately frail residents (Table 2).
Table 2. Advancing frailty and the prevalence of stroke risk factors in care home residents aged ≥65 years with atrial fibrillation
Factors associated with OAC prescription
From unadjusted analyses (Table 3), factors associated with OAC non-prescription included increasing age and prescription of antiplatelet therapy. Conversely, stroke risk factors such as prior stroke (ischaemic, haemorrhagic, and stroke of unknown origin), TIA, hypertension, HF, smoking history, VTE, diabetes, and PVD were associated with OAC prescription. Male sex, advancing frailty, harmful alcohol use, major bleeding, cancer, pulmonary disease, renal disease, prescription of non-steroidal anti- inflammatory drugs (NSAIDs), and care home entry from 2011 were also associated with OAC prescription. All variables had a significance level <0.05.
Table 3. Association between care home resident characteristics and the prescription of oral anticoagulation for atrial fibrillationa
In the multivariate model (Table 3 and Figure 2), advancing age (aOR 0.96 per 1-year increase, 95% CI = 0.95 to 0.96, P<0.001) and prescription of antiplatelet therapy remained as factors significantly associated with OAC non-prescription (aOR 0.91, 95% CI = 0.84 to 0.98, P = 0.014). Prior VTE (aOR 4.06, 95% CI = 3.17 to 5.20, P<0.001), ischaemic stroke (aOR 1.51, 95% CI = 1.37 to 1.67, P<0.001) and HF (aOR 1.46, 95% CI = 1.35 to 1.58, P<0.001) were the stroke risk factors most strongly associated with OAC prescription. Dyslipidaemia, smoking history, stroke of unknown origin, and TIA were also other stroke risk factors independently associated with OAC prescription. There was no significant association found between hypertension and OAC prescription.
Figure 2. Factors associated with prescription of oral anticoagulationa in new care home residents aged ≥65 years with atrial fibrillation, using a multivariable adjusted model. The reference for frailty categories is no frailty. Multivariate model adjusted for dyslipidaemia, smoking history, cancer diagnoses, year of care home entry ≥2011, and individual components of CHA2DS2VASc and HAS-BLED risk assessment scores. a Prescription within 6 months before care home entry used as a proxy for prescription at the point of care home entry.
NSAID = non-steroidal anti-inflammatory drug. OAC = oral anticoagulant. OR = odds ratio.
Other independent predictors of OAC prescription included male sex (aOR 1.09, 95% CI = 1.01 to 1.18, P = 0.024), advancing frailty (mild: aOR 4.61, 95% CI = 3.95 to 5.38, P<0.001; moderate: aOR 6.69, 95% CI = 5.74 to 7.80, P<0.001; severe: aOR 8.42, 95% CI = 7.16 to 9.90, P<0.001), major bleeding (aOR 1.35, 95% CI = 1.23 to 1.48, P<0.001), prescription of NSAIDs (aOR 1.75, 95% CI = 1.51 to 2.02, P<0.001) and care home entry from 2011 onwards (aOR 1.91, 95% CI = 1.76 to 2.06, P<0.001).
The variance inflation factor was <1.5 for all covariates (see Supplementary Table S6). When age was included as a categorical variable, the same covariates were identified as predictors of OAC prescription or non-prescription (see Supplementary Table S7). When people who had a major bleeding event and evidence of OAC prescription within 6 months before care home entry were excluded, the positive association between OAC prescription and major bleeding was attenuated (aOR 1.12, 95% CI = 1.01 to 1.23, P = 0.028) (see Supplementary Figure S2).
