Standardized mortality ratio and seasonal fluctuations of mortality in Parkinson's disease.

Unlabelled: In chronic diseases with low lethality and prolonged progression Parkinson's disease (PD), the standardized mortality ratio (SMR) is more informative in comparison with mortality rates which do not reflect adequately the severity of the disease.

Aim: The aim of the study was to determine the standardized mortality ratio, the absolute excess risk and the indices for seasonal fluctuations of mortality in patients with Parkinson's disease.

Material And Methods: The mortality in patients with PD and in the referent population (regardless of cause) was studied over a 3-year period (2002-2004) in the district of Plovdiv, Bulgaria, with mean population of 711,179 people and total number of patients with PD--2274. Employing document analyses the number of deaths in patients with PD, as well as the total number of deaths in the region were determined. We used the following primary sources of information: the register of patients with PD, developed by the Center for PD at the University Hospital in Plovdiv, containing electronic records of 2274 PD patients (2030 registered with PD by 01.01.2002 and 244 newly registered during the period 2002-2004); the official register of deaths, containing information for 28423 deaths in the district of Plovdiv. Combining the two registers we found out 617 deaths of patients with PD at the mean age of 78.24 years (range 46-94). Actual yearly data on the number, age distribution of the population and deceased for each year of the observed period were obtained from the National Statistical Institute.

Results: On the basis of 617 deceased patients with PD we calculated the standardized mortality ratio--3.6 (95% Confidence interval (CI) 3.37; 3.95) and the absolute excess risk (AER)--0.1967. Higher indices of mortality were found in the autumn-winter months.

Conclusion: Among the population with PD, mortality rate is three times as high as that in the referent population. PD adds about 20% additional risk of death in patients with the disease. Higher mortality is present in PD patients in the autumn-winter months, when their mobility is confined, and inflammatory diseases and traumas in the elderly are more frequent.