The Department of Experimental Medicine - Section of Hygiene, Occupational Medicine, Forensic Medicine of the Second University of Naples, the Section of Neurology of the Second University of Naples and the Mediterranean Neurological Institute NEUROMED, IRCCS are involved in the realization of a research project aimed at studying the correlation between environmental and occupational exposure to metals (copper, iron and manganese) and Parkinson disease in order to increase the knowledge of these possible risk factors and highlight an eventual predictive-diagnostic meaning of possible discrepancies in the content of these elements; secondly the collected data could be used for assessing the association (odd ratio-OR) between pathologies and different risk factors (for example smoking habits, professional exposure and so on).

During the selection of the sample it is essential to consider all the variables that could provoke an alteration in the levels of the indicators examined in the biological fluids investigated.

The adoption of strict criteria for inclusion and exclusion, which differ from metal to metal, is therefore necessary to establish the presence / absence of possible confounding factors that could affect the analysis or interpretation of the data.

It is to be noted also that the number of required participants in a study of MB must be sufficiently large to allow an adequate statistical analysis: the more limited the group of subjects included in the study is, the broader the variability of the data due to inter-individual and methodological differences.

In light of this, some variables, such as age and sex, will be firstly neglected and other potential confounding factors will be considered such as, for example, smoking habits.

Based on the purpose of the research project, the following criteria for exclusion will be considered:

• diseases that may interfere with toxicokinetics of the analyzed metals;
• pharmacological therapy;
• habit-forming additives consumption (excessive alcohol consumption);
• altered physiological states (pregnancy, strenuous physical exercise, recent meal, stress, psychological disorders);

On the contrary, the basic criteria for inclusion in the study are:

• age: subjects of working age, between 18 and 65 years;
• diagnosis of Parkinson's disease (using the criteria of the "London Brain Bank")

Regarding the criteria of partition or stratification of the subjects, the type and number of the possible partitions are conditioned by the sample size; indeed it is essential to ensure a sufficient number of cases (and if possible a similar number of cases) in the various layers to have correct statistical results. It was recommended that the minimum number of subjects per layer must be equal to 80.

In order to collect all the necessary information for the inclusion of subjects in the study and the subsequent stratification of the data, an anonymous questionnaire was realized and administered to each recruited subject.

The questionnaire deals with the environment and the lifestyle and work habits of every participant and it consists of multiple choice questions and free response questions and is divided into macro areas: identification data for data processing; place of residence; professional activity; extraprofessional activities; eating habits; habit-forming additives consumption; medical history.

Each question will be transformed into a "continue" or "categorical" variable in order to be able to build and constantly update a database summarizing the collected data and allowing the statistical analysis of the results.

Each subject enrolled will be also asked to sign a consent form, which states that he or she voluntarily take part to the study, after being informed about the purpose of the study and the analysis of both biological samples and personal data.

The guarantee of anonymity for people recruited for this study is provided by an anonymous questionnaire which do not contain personal data, which are collected only in the consent form, separately from the questionnaire.

EXCLUSION CRITERIA:

• diseases that may interfere with toxicokinetics of the analyzed metals;
• taking medication;
• taking discretionary agents (excessive alcohol consumption);
• altered physiological states (pregnancy, strenuous physical exercise, recent meal, stress, psychological disorders);

INCLUSION CRITERIA:

• age: subjects of working age, between 28 and 70 years;
• diagnosis of Parkinson's disease (using the criteria of the "London Brain Bank")

Cases: subjects of both sexes with at least 10 years of work seniority with diagnosis of Parkinson's disease, coming from Neuromed IRCCS and Second University of Naples Controls: healthy subjects matched by age, sex, lifestyle habits and areas of residence, work seniority.