Showing papers by "Honglei Chen published in 2006"

Pesticide exposure and risk for Parkinson's disease

Abstract: Objective: Chronic, low-dose exposure to pesticides is suspected to increase the risk for Parkinson’s disease (PD), but data are inconclusive. Methods: We prospectively examined whether individuals exposed to pesticides have higher risk for PD than those not exposed. The study population comprised participants in the Cancer Prevention Study II Nutrition Cohort, a longitudinal investigation of US men and women initiated in 1992 by the American Cancer Society. Follow-up surveys were conducted in 1997, 1999, and 2001. The 143,325 individuals who returned the 2001 survey and did not have a diagnosis or symptoms of PD at baseline (1992) were included in the analyses. Results: Exposure to pesticides was reported by 7,864 participants (5.7%), including 1,956 farmers, ranchers, or fishermen. Individuals exposed to pesticides had a 70% higher incidence of PD than those not exposed (adjusted relative risk, 1.7; 95% confidence interval, 1.2–2.3; p 0.002). The relative risk for pesticide exposure was similar in farmers and nonfarmers. No relation was found between risk for PD and exposure to asbestos, chemical/acids/solvents, coal or stone dust, or eight other occupational exposures. Interpretation: These data support the hypothesis that exposure to pesticides may increase risk for PD. Future studies should seek to identify the specific chemicals responsible for this association. Ann Neurol 2006;60:197–203

Incidence and Trends of Stroke and Its Subtypes in China Results From Three Large Cities

Abstract: Background and Purpose— To examine the incidence and trends of stroke and its major subtypes during the 1990s in 3 cities in China. Methods— Stroke cases registered between 1991 to 2000 were initially identified through the stroke surveillance networks established in Beijing, Shanghai, and Changsha, and then confirmed by neurologists. Results— The age-standardized incidence rates per 100 000 person years of overall first-ever stroke were 135.0 (95% CI, 126.5 to 144.6) in Beijing, 76.1 (70.6 to 82.6) in Shanghai, and 150.0 (141.3 to 160.0) in Changsha during the 1990s. Incidence of ischemic stroke (IS) was highest in Beijing, followed by Changsha and Shanghai; for intracerebral hemorrhage (ICH), the highest rate was found in Changsha, followed by Beijing and Shanghai. The same order as ICH was also observed for subarachnoid hemorrhage. The age-adjusted incidence of overall stroke and ICH for individuals ≥55 years of age in our populations was generally higher than that from Western populations. During the 1990s, ICH incidence decreased significantly at a rate of 12.0% per year in Beijing, 4.4% in Shanghai, and 7.7% in Changsha; in contrast, except for Changsha, IS incidence increased in Beijing (5.0% per year) and Shanghai (7.7%). Conclusions— There is a geographic variation in the incidence of stroke and its subtypes among these 3 cities, but the incidence of overall and hemorrhagic stroke in China is generally higher than that in the Western countries. Interestingly, the decrease in ICH and increase in IS during the past decade may reflect some underlying changes of risk factors in Chinese populations.

Survival of Parkinson's disease patients in a large prospective cohort of male health professionals.

Abstract: Parkinson's disease (PD) patients have higher mortality than individuals without PD. However, most of the previous studies were based on prevalent cases and few examined the potential effects of duration and smoking on the survival of PD patients. We compared the survival experience of 288 men with incident PD diagnosed between 1986 and 2000 with that of 51,012 men free of PD in the Health Professionals Follow-up Study. As of January 2002, 92 deaths occurred among PD cases and 8,485 among men without PD. After controlling for age, men with PD had 60% higher mortality than those without PD (95% CI: 1.3-2.0). PD mortality was strongly related to disease duration: compared with men without PD, the age-adjusted relative risk for PD patients was 1.1 during the first 5 years from diagnosis, 2.3 from 5 to 10 years, and 3.5 after 10 years (P 30 pack-years vs. never smokers, relative risk, 2.0; P < 0.0001 for trend), but this association was not observed among PD patients (RR: 1.0; P = 0.95 for trend). This study confirms that PD patients have a higher mortality than individuals without PD and that the excess mortality increases with disease duration. However, smoking seems to impose little additional risk among PD patients in this large cohort of health professionals.

A Prospective Study of Night Shift Work, Sleep Duration, and Risk of Parkinson's Disease

Abstract: The authors prospectively investigated whether working rotating night shifts was associated with the risk of Parkinson’s disease among 84,794 female nurses who reported years of night shift work in 1988 (the US Nurses’ Health Study). After 975,912 person-years of follow-up (1988–2000), 181 incident Parkinson’s disease cases were documented. Compared with nurses who never worked rotating night shifts, those with 15 years or more of night shift work had a 50% lower risk of Parkinson’s disease after adjustment for age and smoking (95% confidence interval: 0.26, 0.97; ptrend ¼ 0.01). Sleep duration was positively associated with Parkinson’s disease risk: The relative risk was 1.84 (95% confidence interval: 0.99, 3.42) when comparing nurses who reported 9 or more hours of sleep per day with those who slept 6 hours or less (ptrend ¼ 0.005). These data suggest that working night shifts may be protective against Parkinson’s disease or that low tolerance for night shift work is an early marker of Parkinson’s disease. Conversely, habitual longer sleep duration may be an earlier marker of Parkinson’s disease. Because of the novelty and the exploratory nature of these findings, confirmation is needed.

Blood donations, iron stores, and risk of Parkinson's disease.

Abstract: Iron overload and systemic iron stores may be important in the pathogenesis of Parkinson's disease (PD). We therefore examined the association between blood donations, which reduce body iron stores, and risk of PD in the Health Professionals Follow-Up Study, a large cohort investigation of U.S. men. Our hypothesis was that blood donation reduces the risk of PD by lowering systemic iron stores. Although the number of blood donations was inversely related to the ferritin levels in a subsample of the study population, no association was found between the number of blood donations and risk of PD (P for trend = 0.6). Unexpectedly, the risk of PD was higher among men who reported recent multiple blood donations (P for trend = 0.05). The results of this study do not support the hypothesis that reduced systemic iron stores lower the risk of PD.

Circulating melatonin levels: possible link between Parkinson's disease and cancer risk?

Abstract: Lower rates of cancer mortality/incidence in patients with Parkinson’s disease (PD) have given rise to speculations about risk or preventative factors common to both diseases, including life-style factors (such as smoking) and genetic susceptibility. Melatonin, a hormone known for its sleep regulatory effects, may play an important role in carcinogenesis as suggested by substantial laboratory and less direct epidemiologic evidence. Particularly, a reduction in melatonin, such as experienced by persons who are exposed to light at night, appears to increase cancer risk. Variations in melatonin levels have been linked to PD in several different ways. Some studies show higher morning melatonin levels in PD patients than in healthy controls. One could speculate that the sleep disorders that affect almost two thirds of those suffering from PD and can precede PD motor symptoms by several years may be associated with variations in melatonin levels. Moreover, in animal models, interventions that increase the bioavailability of melatonin appears to increase the severity of parkinsonian symptoms, whereas reduction in melatonin by pinealectomy or exposure to bright light can enhance recovery from parkinsonisms symptoms. Finally, preliminary epidemiological evidence suggests that longer years of working night shifts is associated with a reduced risk of PD among participants of the Nurses’ Health Study (NHS), whereas longer hours of sleep appear to increase their risk. In sum, while lower melatonin concentrations may predict a higher cancer risk, there is also some evidence that they may be associated with a lower risk of PD. We therefore hypothesize that elevated circulating melatonin levels in PD patients may contribute to their lower cancer rates.

Auto-Regressive Aperture Extrapolation for Multibaseline SAR Tomography

Abstract: In this paper, a method based on auto-regressive (AR) extrapolation is presented for estimating the heights of multiple scattering centers in multibaseline SAR tomography. The extrapolation algorithm is used to create a large virtual array of multibaseline measurements, which in turn provides enhanced resolution over the traditional FFT-based methods. Since the method is linear, it can also be used to estimate the polarimetric signature, which allows one to identify targets in SAR tomography. This method is compared with the MUSIC algorithm and is shown to work as well or better in most cases.