Seasonality, incidence and prognosis in atrial fibrillation and stroke in Denmark and New Zealand

Abstract

ObjectivesThere are relatively few large studies of seasonal variation in the occurrence of stroke in patients with atrial fibrillation (AF). We investigated the seasonal variation in incidence rates of hospitalisation with stroke in patients from Denmark and New Zealand.DesignCohort study.SettingNationwide hospital discharge data from Denmark and New Zealand.Participants243 381 (median age 75) subjects having a first-time hospitalisation with AF in Denmark and 51 480 (median age 76) subjects in New Zealand constituted the study population. Subjects with previous hospitalisation with stroke were excluded.Primary and secondary effect measuresPeak-to-trough ratio of the seasonal variation in incidence rates of stroke in AF patients adjusted for an overall trend was primary effect measure and was assessed using a log-linear Poisson regression model. Secondary effect measures were incidence rate ratios of AF and 30-day case fatality for stroke patients.ResultsIncidence rates of AF per 1000 person-years in Denmark increased by 5.4% (95% CI 5.3% to 5.7%) for patients aged <65 and 5% (95% CI 4.9% to 5.1%) for patients aged ≥65, whereas the increase was 0.2% (95% CI −0.2% to 0.6%) for patients aged <65 and 2.6% (95% CI 2.4% to 2.8%) for patients aged ≥65 in New Zealand. In Denmark 36 088 subjects were hospitalised with stroke, and 7518 subjects in New Zealand, both showing peaks during winter with peak-to-trough ratios of 1.22 and 1.27, respectively and a decreasing trend. The 30-day case fatality risk for stroke patients having AF is now (2000–2008) about 20% in both countries.ConclusionsAlthough incidence rates of hospitalisation with stroke in patients with AF have decreased in recent years, stroke remains a common AF complication with a high case fatality risk. The marked winter peak in incidence rates of hospitalisation with stroke in AF patients suggests that there are opportunities to reduce this complication. Further studies are necessary to identify how to optimise treatment of AF and prevention of stroke.

Modeling gradually changing seasonal variation in count data using state space models: a cohort study of hospitalization rates of stroke in atrial fibrillation patients in Denmark from 1977 to 2011

“…Also, when applying DGLMs in assessing seasonal variations in frequencies of hospitalisations, as opposed to GLMs, further details regarding model parameters may be provided. In Christensen et al, 2012, an analysis similar to the analysis proposed in this study and on the same data was performed [48]. A GLM, assuming data being Poisson distributed and specifying the linear predictor as a superposition of a seasonal variation with periods of 12, 6 and 3 months, and 6 weeks and an overall trend specified as a cubic spline, was fitted to the time series, y t , t = 1,…, n .…”

Vitamin D deficiency and atrial fibrillation

“…Although 25[OH]D is commonly used to clinically assess vitamin D status, it may not be sufficient as a marker for research purposes due to variation in results from different assays. In particular, liquid chromatography-mass spectrometry assays have been found to give relatively high results compared to radioimmunoassays [24].…”

“…[12,25,26] Shoben et al [14] illustrated a sinusoidal pattern for mean monthly 25[OH]D concentration, with low levels throughout winter corresponding to the seasonal increase in AF incidence, suggesting that vitamin D levels may be responsible. As such, the seasonal variation in vitamin D levels due to changes in ultraviolet exposure must be taken in to account when designing and interpreting studies investigating vitamin D and AF.…”

Seasonal trends in hypertension in Poland: evidence from Google search engine query data

“…A similar search was done regarding obstructive sleep disorder breathing, showing large differences depending on the time of the year [15]. It is worth mentioning that comorbidities accompanying HT tend to exacerbate in the winter months [16][17][18]. HT is no different, and BP values in this period are higher [19].…”