In this elderly hospital-based population, we found that NOAF was prevalent during follow-up. Independent risk factors for NOAF included hypertension and HF. The HATCH score showed moderate predictive accuracy for NOAF. Among subgroups of patients, such as those ≥75 years, with diabetes, renal dysfunction and structural heart disease, the performance of the HATCH score for predicting NOAF ranged from poor to moderate.
Multiple international guidelines and large-scale screening studies regarding AF have recommended or use age as the single criteria for making screening strategies[5, 25, 26]. However, with the surging number of the aging population, massive screening among the elderly is limited with cost-effectiveness. Considering that the elderly population generally represents a high-risk group for developing NOAF, stratifying this group of patients into diverse risk categories may help to identify those at real high risk or exclude those at low risk from unnecessary screening. In the present study, among the elderly population, the risk of NOAF was 1.71 per 100 patient-years which was higher than those from the community-based Yunnan Medical Insurance database, which was 0.28-0.77 per 100 patient-years in subjects aged ≥61 years[24]. In another Japanese cohort of male subjects, among the elderly population, the incidence was 2.58 (if body mass index <25 kg/m2) and 5.53 (if body mass index ≥25 kg/m2) per 100 patient-years[27], which was higher than the present study, probably due to the all-male gender in the Japanese cohort.
Risk factors for NOAF have been largely reported previously[28–35], which include aging, hypertension, HF, renal dysfunction, CAD, structural heart disease, obesity, etc. However, in the present study, we found that among elderly subjects, only hypertension and HF were independently related to the development of AF. The other underlying risk factors did not show significance after adjustment. This result could be attributed to the limited sample size and event rate in represent subgroups of patients. For example, age≥75 years (HR 1.21, P=0.059) and CAD (HR 1.71, P=0.060) are not too far away from showing statistical significance. On the other hand, this result demonstrated that well-controlled blood pressure and HF may be necessary for reducing cardiovascular events, including the development of AF.
Previously, the HATCH score has been developed for predicting AF progression from paroxysmal to persistent subtypes[6]. Lately, this score has also been validated to predict AF in diverse populations[14, 16, 17, 19–22]. The reason for the generalization application of this score is that the pathophysiology processes of AF development and AF progression share multiple common risk factors, such as HF and hypertension, etc. In the present study, the performance of the HATCH score was moderate. Compared with other risk scoring systems showing capability of predicting incident AF, the HATCH score was inferior to the C2HEST and the HAVOC scores, but superior to the CHA2DS2-VASc score. In subgroups of patients, the C-indexes ranged from 0.490 to 0.632. The relatively lower predictive accuracy may be due to unrelated compositions in the scoring system. For example, stroke and transient ischemic attack was not significantly related to AF development in some studies[24, 35, 36], but was enlisted as one of the major risk factors in the HATCH score with 2 points of weight[6]. The development of stroke/transient ischemic attack may reveal those underdiagnosed AF, but not a driven factor for the development of AF.
Strength and limitation
This is the first study assessing the performance of the HATCH score in an elderly hospital-based Chinese population in predicting NOAF. However, limitations exist in the present study. First, we did not have instrumental and biomarker-based variables which have been shown to have the ability for predicting AF. Thus, we could not test whether the addition of these markers could improve the performance of the HATCH score. Second, the relatively limited outcome events may be a major reason for the poor to moderate performance of the HATCH score, which merits further investigations in larger cohorts. Third, not all patients received systematic screening during hospitalization, which may lead to underdiagnosis of AF.