Frailty on the island of Ireland: evidence from the NICOLA and TILDA studies

Background
Aimed to compare the prevalence, characteristics, and associated mortality risk of frailty in Northern Ireland (NI) and the Republic of Ireland (ROI).

Methods
Secondary analysis of the first wave of two nationally representative cohorts, the Northern Ireland Cohort for the Longitudinal Study of Ageing or NICOLA study (N = 8504) and the Irish Longitudinal Study on Ageing or TILDA study (N = 8504). Frailty was assessed using a harmonized accumulation deficits frailty index (FI) containing 30 items. FI scores classified individuals as non-frail (<0.10), pre-frail (0.10–0.24) and frail (≥0.25). Linkage to respective administrative data sources provided mortality information with a follow-up time of 8 years.

Results
The prevalence of frailty was considerably higher in NI compared with the ROI (29.0% compared with 15.0%), though pre-frailty was slightly lower (35.8% and 37.3%, respectively). Age, female sex, and lower socio-economic status were consistently associated with a higher likelihood of both pre-frailty and frailty. In the pooled analysis, both frailty and pre-frailty were higher in NI (RR = 2.68, 95% CIs 2.45, 2.94 and RR = 1.30, 95% CIs 1.21, 1.40, respectively). Frailty was associated with an increased mortality risk in both cohorts, even after full adjustment for all other characteristics, being marginally higher in TILDA than in NICOLA (HR = 2.43, 95% CIs 2.03, 2.91 vs. HR = 2.31, 95% CIs 1.90, 2.79).

Conclusions
Frailty is a major public health concern for both jurisdictions. Further research and monitoring are required to elucidate why there is a higher prevalence in NI and to identify factors in early life that may be driving these differences.