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A case-control study of Parkinson's disease (PD) was conducted in the city …


Biology Articles » Genetics » Ecological Genetics » Genetics, drugs and environmental factors in parkinson's disease (A case-control study) » Results

Results
- Genetics, drugs and environmental factors in parkinson's disease (A case-control study)

Forty-one men and 51 women diagnosed with PD were compared to controls (47 men and 63 women). Average age was 70.55 for PD patients and 68.38 for controls. Present age of subjects with PD (n = 92) ranged from 55 to 78, while controls (n = 110) ranged from 55 to 79. In the group of subjects, 5 individuals were brown and 5 black-skinned; among controls, 12 were brown and 7 were black.

A) Family history: Among subjects, 20.65% (17/92) had a family history of PD. Regarding distribution of relatives affected by the disease, it was found that first degree relatives were associated to 12 cases, second degree relatives were observed in 5 cases, and third degree relatives appeared in 4 cases. Only two controls had a family history of PD.

B) Herbicides and pesticides: From the total of selected individuals for this factor, 6 were diagnosed with PD (6.36%) compared with 3 controls (2.72%). Among the cases where contact with these compounds was reported, 4 individuals had used them during rural residency (all had PD), while the remaining ones had used them in their own houses.

C) Chemical agents: 14 subjects and 4 controls were included. Table 1 shows the chemical products involved. Occupations were: painters, dentists, goldsmiths and car mechanics.

D) Drugs: this variable was present in 22 cases of PD (23.9%); 5.43% of subjects reported not having any perception of parkinsonian symptoms while using mentioned drugs. Four controls (3.63%) with a history associated to the use of parkinsonian drugs were noted. Table 2 shows distribution of drugs involved among subjects and controls. 

E) Trauma: 17 subjects (18.5%) had some relevant history of head trauma, compared with 14 controls (12.7%).

F) Rural living: 26 subjects (28.3%) and 31 controls (28.2%) matched necessary criteria for this variable.

G) Potable water well-source: 26 subjects (28.3%) and 23 controls (20.9%) had a history of well-water intake.

H) Cigarette smoking: 9 subjects (9.8%) and 24 controls (21.8%) were cigarette smokers.

1) Univariate analysis: Table 3 displays results. This method demonstrated that the considered risk factors for the disease were distributed by odd terms as follows: family history 14.05 (CI = 2.98 - 91.38), drugs 11.01 (CI = 3.41 - 39.41), chemical agents 5.87 (CI = 1.48 - 27.23), and cigarette smoking 0.39 (CI = 0.16 - 0.95). The obtained confidence intervals for drugs, chemical agents and family history were considered as inaccurate.

2) Stratified analysis: Drugs and family history variables were confirmed as risk factors, while cigarette smoking was considered a protection factor. Results obtained were: 1 ¾ PD association to the use of drugs presented variations in relation to the odds ratio for the drugs variable (Table 4). Its value of 11.01 (CI = 3.41 - 39.41) underwent the following variations: a) If analyzed among smokers it falls to 6.57 (CI = 0.36 - 221.95); b) Among non-smokers it becomes stable at 11.93 (CI = 3.18 - 52.79). 2 ¾ PD associated to family history indicated that the odds ratio value that was 11.5 (CI = 0.98 - 356.91) among smokers rose to 20.3 (CI = 2.68 - 427.95) among non-smokers. 3 ¾ Cigarette consumption odds ratio underwent the following alterations in relation to use of drugs (Table 5): a) If analyzed among those that made use of drugs, its value is 0.24 (CI = 0.01 - 9.17); b) Among those who did not make any use of drugs, the value is 0.44 (CI = 0.16 - 1.17).

 3) Multivariate analysis: This process used the logistic regression method, where values pertaining to the parameters' estimates (PE), X2 test (chi-square), are presented together with the significance level. Methodology applied considered significance level (SL) equivalent to a probability of 5% (p < 0.05). In order of decreasing importance, factors bearing significant values for PD were: drugs (SL = 0.0001; X2 = 27.58; PE = 2.973), family history (SL = 0.0006; X2 = 4.4; PE = 2.733) and chemical agents (SL = 0.0014; X2 = 10.19; PE = 2.214). No significant values were found associated to rural residency (SL = 0.138; X2 = 2.2; PE = - 1.26), well water (SL = 0.211; X2 = 1.56; PE = 1.12), herbicides and pesticides (SL = 0.271; X2 = 1.21; PE = 0.887) and trauma (SL = 0.887; X2 = 0.02; PE = 0.067).

 


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