Proximity to major roads and highways associated with Alzheimer’s, Parkinson’s disease, dementia and multiple sclerosis
A large Canadian population-based study links living near major roads and highways with higher incidence of non-Alzheimer’s dementia (NAD), Parkinson’s disease (PD), Alzheimer’s disease (AD) and multiple sclerosis (MS).
Road proximity was associated with all outcomes for living <50 m from a major road or <150 m from a highway, with hazard ratios (HRs) for NAD and PAD of 1.14 (95 percent confidence interval [CI], 1.07 to 1.20) and 1.07 (95 percent CI, 0.96 to 1.18), respectively, while the odds ratios (ORs) for AD and MS were 1.19 (95 percent CI, 0.95 to 1.49) and 1.25 (95 percent CI, 0.96 to 1.63). [Environ Health 2020;19:8]
The NAD and PD cohorts comprised 7.3 and 7.4 million person-years of observations. During the follow-up period, 13,170 incident cases of NAD, 4,201 incident cases of PD, 1,277 incident cases of AD and 658 incident cases of MS were identified.
Highways were defined as roads with 115,000 and 200,000 vehicles per day on average, and major roads as having between 15,000 and 18,000 vehicles per day on average.
As well as investigating links between road proximity and cognitive impairment, the researchers evaluated exposure to air pollution and the joint effects of noise and greenness on NAD, PD, AD and MS. “Noise and greenness are spatially correlated with road proximity and traffic-related air pollution, and may have some impact on neurological disorders,” hypothesized the researchers. [Occup Environ Med 2009;66:347-350; Urban For Urban Green 2015;14:806-816] “While there were small effects of noise on both NAD and PD, including noise in models had essentially no impacts on air pollutant HRs,” they discovered.
In the cohort of NAD, road proximity was moderately correlated with air pollution (eg, r=0.49 between major road <50m or highway <150m and black carbon). Greenness was negatively correlated with air pollution (eg, r=−0.48 between greenness and nitric oxide [NO]).
Air pollutants, except for NO, were generally associated with slightly increased HRs for both NAD and PD; PM2.5, in particular, was associated with increased HRs for NAD, PD and MS. “Both road proximity and air pollution had greater effects on incidence of NAD and PD among people aged under 65 years,” highlighted the researchers.
The effects of road proximity for NAD and PD were attenuated after accounting for greenness, with reductions (0.3 percent to 6.2 percent) in HRs observed in all proximity categories. “The protective effect of greenness was more evident for PD compared with NAD,” observed the researchers.
Greenness provided a large (11 percent to 28 percent) attenuation of OR for AD. “However, it did not attenuate the OR for MS and there were some indications of increased ORs after accounting for greenness,” noted the researchers.
“Living near roads was linked with higher incidence of NAD, PD, AD and MS. Although results were not entirely consistent, air pollution was linked with NAD and PD, but not AD or MS. Greenness was found to have some protective effects, while impacts of noise were generally null,” summed up the researchers.