Papers by Penka A Atanassova
Nature Precedings, 2008
Best available descriptions of malaria incidence and mortality dynamics are important to better p... more Best available descriptions of malaria incidence and mortality dynamics are important to better plan and evaluate the implementation of programs to monitor (e.g., remote sensing) and control the disease, especially in endemic zones. This was stressed recently by Cibulskis et al (2007) in the view of completeness of monthly reporting for cerebral malaria admissions in Papua New Guinea (latitude 6 degree S, 1987-1996). Notably, regardless of the rate of its completeness, the temporal dynamics of admissions was preserved over the years, however, neither raw data nor results on further analyses about eventual inter-annual cyclic components (periods T>1 year) were provided despite obvious graphical patterns for such a specific time structure (chronome). Interestingly, in a recent analysis by Gomez-Elipe et al (2007) on monthly malaria notifications in Burundi, at almost the same latitude (province of Karuzi, >3 degree S, 1997-2001), the data have shown neither trend not periodic os...
Central European Journal …, 2008
Only few follow-up studies have studied in detail the role of most important risk factors, but no... more Only few follow-up studies have studied in detail the role of most important risk factors, but no reports were found on critical values (cut-offs) for such factors in prospectively predicting cerebrovascular events (CVE) in patients with minor ischaemic stroke (MIS). Estimates of predictive importance of such cut-offs may better inform and contribute to optimize treatment. This was a post-hoc modelling study with unique data from Bulgaria on 54 consecutive patients with MIS, aged ł 40, followed for 12 months for nonfatal or fatal CV events. A set of routine clinical demographic and known risk factors (SBP, DBP, HDL cholesterol, etc.) were explored using univariate statistics and multivariate regression models to identify the most important independent predictors of secondary CVE. An artificial neural network (ANN) model, irrespective of usual statistical constraints, also confirmed the specific role and importance of identified predictors. A receiver operating characteristics (ROC) curve and stratified survival analyses were used to define the best cut-off of most important predictors and validate the final model. During follow-up period of 11.1±2.4 months, 8 secondary CV events (14.8%) were observed only in males with MIS at the 5.8±2.7 months mark. No difference in age of patients with CV event (61.1±12.6 years) vs. those without (62.1±9.6 years) was found (p>0.05). The one-year risk for CVE was.15% (95%CI 7.1, 27.7%). The two most important risk factors in patients with versus without CV events were acute MIS onset (62.5 vs. 13.0%) and mean DBP at day 30 post-MIS (101.3±9.9 vs. 92.3±10.8 mmHg), with a relative importance by ANN of 20.92 versus 15.9 points, respectively. At multivariate logistic analysis only MIS onset and DBP were independently associated with the risk for secondary CVE (79.6% model accuracy, p model=0.0015). An increase of DBP with 1 mmHg was associated with 8% higher risk of CVE [adjusted OR=1.08 (95%Cl 1.004, 1.158)]. With this method, a novel cut-off predictive DBP value of 95 mmHg (ROCAUC=0.79, 95%Cl 0.60, 0.99, p=0.009) for CV events in patients with MIS has been found. In conclusions the new DBP cut-off (sensitivity >87%, specificity >69%) clearly discriminated between absence and presence of secondary CVE as also confirmed by stratified survival analysis (7 vs. 1 events, plog-rank =0.0103). This cut-off may be applied to better precisely evaluate and define, as earlier as possible, MIS patients at increased risk of secondary CV events.
Background: The subclinical cerebrovascular disease (SCVD) is an important public health problem ... more Background: The subclinical cerebrovascular disease (SCVD) is an important public health problem with demonstrated prognostic significance for stroke, future cognitive decline, and progression to dementia. The earliest possible detection of the silent presence of SCVD in adults at age at risk with normal functioning is very important for both clinical doctors and scientists.
Epidemiology and Infection, 2013
Data on the dynamics of malaria incidence, admissions and mortality and their best possible descr... more Data on the dynamics of malaria incidence, admissions and mortality and their best possible description are very important to better forecast and assess the implementation of programmes to register, monitor (e.g. by remote sensing) and control the disease, especially in endemic zones. Semi-annual and seasonal cycles in malaria rates have been observed in various countries and close similarity with cycles in the natural environment (temperature, heliogeophysical activity, etc.), host immunity and/or virulence of the parasite suggested. This study aimed at confirming previous results on malaria cyclicity by exploring whether trans-year and/or multiannual cycles might exist. The exploration of underlying chronomes (time structures) was done with raw data (without smoothing) by linear and nonlinear parametric regression models, autocorrelation, spectral (Fourier) and periodogram regression analysis. The strongest cyclical patterns of detrended malaria admissions were (i) annual period of 1 . 0 year (12 months or seasonality) ; (ii) quasi-biennial cycle of about 2 . 25 years ; and (iii) infrannual, circadecennial cycle of about 10 . 3 years. The seasonal maximum occurred in May with the minimum in September. Notably, these cycles corresponded to similar cyclic components of heliogeophysical activity such as sunspot seasonality and solar activity cyclicities and well-known climate/weather oscillations. Further analyses are thus warranted to investigate such similarities. In conclusion, multicomponent cyclical dynamics of cerebral malaria admissions in Papua New Guinea were observed thus allowing more specific analyses and modelling as well as correlations with environmental factors of similar cyclicity to be explored. Such further results might also contribute to and provide more precise estimates for the forecasting and prevention, as well as the better understanding, of the dynamics and aetiology of this vector-borne disease.
Central European Journal of Biology, 2010
Best available descriptions of malaria incidence and mortality dynamics are important to improve ... more Best available descriptions of malaria incidence and mortality dynamics are important to improve and evaluate the implementation of programs to monitor (e.g., remote sensing) and control disease, especially in endemic zones. High-frequency (e.g., semi-annual and seasonal) cycles in malaria incidence have been observed in various countries and they coincide with cycles in the natural environment (e.g., temperature, heliogeophysical activity, etc.).
Multicomponent cyclicity in monthly suicides (periods T = 18, 46 and 198 months) was found and cl... more Multicomponent cyclicity in monthly suicides (periods T = 18, 46 and 198 months) was found and close similarity with heliogeophysical activity (HGA) suggested by Dimitrov in 1999. The current report aimed at scrutinizing the results on suicide annual cyclicity (seasonality) in Slovenia as reported by Oravecz et al in 2007 as well as at analyzing suicide data from Finland in this regard. We postulated that: (i) trans-year (12-24 months) or far-trans-year long-term cycles of suicides might interfere with their seasonality; and (ii) associations to environmental factors with alike cyclicity (e.g. HGA, temperature) could exist. Annual suicide incidence from Oulu, Finland over years 1987-1999 was analyzed. Annual data on solar activity (sunspot index Rz or Wolf number), planetary geomagnetic activity (aa-index) and local daily mean temperatures were used. The exploration of underlying chronomes (time structures) was done by periodogram regression analysis with trigonometric approximation...
Journal of …, 2009
Quantitative data on melatonin in stroke patients are scarce. Gender-and age-matched cross-sectio... more Quantitative data on melatonin in stroke patients are scarce. Gender-and age-matched cross-sectional casecontrol study in 33 patients with ischaemic stroke (IS) was performed and associations between nocturnal melatonin and other factors (e.g., cortisol) evaluated. Clinical and laboratory (e.g., melatonin and cortisol) measurements (3 and 8 a.m.) with statistical techniques [e.g., multifactorial regressions, receiver operating characteristics (ROC) curve and curvilinear estimations] were used. We identified mean value and 95% confidence interval (69.70 pg/ml, 95% CI 53.86-85.54) for control levels of nocturnal melatonin in healthy subjects. The patients with stroke had lower melatonin (48.1±35.9 pg/ml) and higher cortisol (297.3±157.8 nmol/l) at 3 a.m. (p<0.05) but not at 8 a.m. (p>0.05). The stroke was the strongest factor of disturbed nocturnal cortisol (p<0.001) while decreased melatonin depended on the stroke (p=0.010) and gender (p=0.018). In the same time, vice versa, only nocturnal measures were associated with increased probability of presence of stroke (accuracy>75%, p-model<0.001). Thus, a hypothesis that a decrease of melatonin with 1.0 pg/ml might be associated with >2% increase in the probability of presence of stroke [adjusted odds ratio = 1.020 (95%CI 1.002-1.037)] was also suggested. ROC curve (0.67, p=0.0119) and optimisation techniques indicated that a novel best cut-off<51.5 pg/ml for decreased nocturnal melatonin in the view of the presence of stroke (odds ratio = 3.12, p=0.0463) might exist. The classification performance of such cut-off might be confirmed by existing nocturnal melatonin and cortisol differences between the sub-groups; potential differences in diurnal melatonin were also suggested. In conclusion, a novel melatonin cut-off of 51.5 pg/ml may be associated with the presence of ischaemic stroke. As a single marker (84% sensitivity, 74% specificity), its hypothesised modelling performance was independent of age, gender and cortisol. These new results, including the suggested hypothesis, might be further tested in follow-up (cohort), longitudinal studies and be applied to further explore melatonin disturbances as targets in high-risk pre-stroke and post-stroke patients.
Data on the dynamics of malaria incidence, admissions and mortality and their best possible descr... more Data on the dynamics of malaria incidence, admissions and mortality and their best possible description are very important to better forecast and assess the implementation of programmes to register, monitor (e.g. by remote sensing) and control the disease, especially in endemic zones. Semi-annual and seasonal cycles in malaria rates have been observed in various countries and close similarity with cycles in the natural environment (temperature, heliogeophysical activity, etc.), host immunity and/or virulence of the parasite suggested. This study aimed at confirming previous results on malaria cyclicity by exploring whether trans-year and/or multiannual cycles might exist. The exploration of underlying chronomes (time structures) was done with raw data (without smoothing) by linear and nonlinear parametric regression models, autocorrelation, spectral (Fourier) and periodogram regression analysis. The strongest cyclical patterns of detrended malaria admissions were (i) annual period of 1·0 year (12 months or seasonality); (ii) quasi-biennial cycle of about 2·25 years; and (iii) infrannual, circadecennial cycle of about 10·3 years. The seasonal maximum occurred in May with the minimum in September. Notably, these cycles corresponded to similar cyclic components of heliogeophysical activity such as sunspot seasonality and solar activity cyclicities and well-known climate/weather oscillations. Further analyses are thus warranted to investigate such similarities. In conclusion, multicomponent cyclical dynamics of cerebral malaria admissions in Papua New Guinea were observed thus allowing more specific analyses and modelling as well as correlations with environmental factors of similar cyclicity to be explored. Such further results might also contribute to and provide more precise estimates for the forecasting and prevention, as well as the better understanding, of the dynamics and aetiology of this vector-borne disease.
Copyright Note: This paper is copyrighted to Cambridge University Press. The full reference reads as: Dimitrov, B.D., Valev, D., Werner, R. and Atanassova, P.A. (2013) Cyclic patterns of cerebral malaria admissions in Papua New Guinea for the years 1987-1996. Epidemiology and Infection, 1-11. (doi:10.1017/S0950268812003111). (PMID:23339988). The link to the online edition of the Journal can be found at the Cambridge Journals Online at DOI: http://dx.doi.org/10.1017/S0950268812003111
Central European Journal of Medicine, 2006
Page 1. DOI: 10.2478/s11536-006-0018-7 Research article CEJMed 1(2) 2006 148157 Abnormal ECG pat... more Page 1. DOI: 10.2478/s11536-006-0018-7 Research article CEJMed 1(2) 2006 148157 Abnormal ECG patterns during the acute phase of subarachnoid hemorrhage in patients without previous heart disease Penka A. Atanassova1 ...
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Papers by Penka A Atanassova
Copyright Note: This paper is copyrighted to Cambridge University Press. The full reference reads as: Dimitrov, B.D., Valev, D., Werner, R. and Atanassova, P.A. (2013) Cyclic patterns of cerebral malaria admissions in Papua New Guinea for the years 1987-1996. Epidemiology and Infection, 1-11. (doi:10.1017/S0950268812003111). (PMID:23339988). The link to the online edition of the Journal can be found at the Cambridge Journals Online at DOI: http://dx.doi.org/10.1017/S0950268812003111
Copyright Note: This paper is copyrighted to Cambridge University Press. The full reference reads as: Dimitrov, B.D., Valev, D., Werner, R. and Atanassova, P.A. (2013) Cyclic patterns of cerebral malaria admissions in Papua New Guinea for the years 1987-1996. Epidemiology and Infection, 1-11. (doi:10.1017/S0950268812003111). (PMID:23339988). The link to the online edition of the Journal can be found at the Cambridge Journals Online at DOI: http://dx.doi.org/10.1017/S0950268812003111