Air pollution, a novel risk factor for late life dementia? Dr Ruth Peters
Dementia • Late 18th century: from Latin, from demens , dement- 'out of one's mind‘ • a serious mental disorder caused by brain disease or injury, that affects the ability to think, remember and behave normally (OED) • The word dementia describes a set of symptoms that may include memory loss and difficulties with thinking, problem-solving or language. These changes are often small to start with, but for someone with dementia they have become severe enough to affect daily life. (Alzheimer’s Society UK) An umbrella term for a syndrome (includes Alzheimers disease, vascular dementia, multi-infarct dementia etc:)
Cognitive decline • A deterioration in cognitive function greater than that expected with age • Dementia is diagnosed when cognitive decline is severe enough to interfere with activities of daily living • Cognitive function includes a wide range of processes associated with day to day activities • Assessment of function via neuropsychological tests
Perceptual-motor function Visual perception Visuoconstructional reasoning Perceptual-motor coordination Executive function Planning Language Decision making Object naming Working memory Word finding Responding to feedback Fluency Inhibition Grammar and syntax Cognitive Flexibility domains Learning and memory Social cognition Free recall Recognition of Cued recall emotions Recognition memory Theory of mind Semantic and autobiographical Insight long-term memory Implicit learning
Why do we care? Dementia is a distressing, disabling, degenerative and eventually fatal condition Lobo et al 2000 There is no imminent cure
What can we do? • Emphasis now turning to prevention/delay of cognitive decline • Huge amount of work looking at risk factors • Lifestyle risk factors • Clinical risk factors • Public Health messages starting to include dementia as a key non-communicable disease (See Blackfriars Consensus UK https://www.gov.uk/government/news/call-for-new-policy-focus-on- brain-health-to-reduce-the-risk-of-dementia )
Lifestyle risk factors Alcohol? Smoking Low education Obesity Lack of physical activity Poor diet
Clinical Risk factors Hypertension High cholesterol Diabetes
Inflammatory processes smoking High cholesterol Cognitive obesity decline/dementia Low Diabetes Hypertension physical activity Lifestyle risk factors Clinical risk factors Outcome Increasing cardiovascular risk
Conversation with a cardiologist…..
Air pollution Particulate matter • Ultra fine particulate matter <0.1µm (UFPM) • Fine particulate matter <2.5µm (PM 2.5 ) • Coarse particulate Matter <10 µm (PM 10 ) Gaseous pollutants • Ozone • Nitrogen dioxide • Carbon monoxide http://www.engineeringtoolbox.com/ • Sulphur dioxide particle-sizes-d_934.html
Air pollution and cardiovascular risk Evidence for long term exposure and increased risk of cardiovascular and cerebrovascular events Level of Exposure to Fine Particulate Matter and the Risk of Death from Cardiovascular Causes in Women.
Furthermore….
Short term exposure also associated with increased risk…
Inflammation and air pollution Block & Calderon-Garciduenas 2009 Trends in Neuroscience doi:10.1016/j.tins.2009.05.009
Air pollution and risk of cognitive decline/dementia Systematic review • Searched MEDLINE, Embase and Psych INFO from inception to 1 st Nov 2013 using terms related to air pollution and dementia or cognitive function. • 1551 records after duplicates removed • 10 full text articles • 8 retained of those…. • 6 reported on historical exposure to air pollution and later cognitive function ‘prevalence’ studies • 2 reported on change in cognitive function, incident cognitive decline
Air pollution and risk of cognitive decline/dementia Prevalence studies 1. Department of Veterans Affairs Normative Aging Study (NAS), 680 men, USA 2. MOBILIZE Boston Study, 765 men and women, USA 3. Chinese longitudinal Health Longevity Survey (CLHLS) 3 rd wave, 7358 men and women, China 4. Chinese longitudinal Health Longevity Survey (CLHLS) 3 rd and 4 th waves, 15973 men and women, China 5. Study on the influence of lung function inflammation and Aging (SALIA), 4874 women, Germany 6. 3 rd National Health and Nutrition Examination Survey (NHANESIII), 1479 men and women, USA.
Air pollution assessment of outcome Mini Mental State Exam Short screening test • NAS, Mobilize Boston, CLHLS 3 rd wave, CLHLS 3 rd and 4 th waves Neuropsychological Tests used vary by study, little overlap test battery • NAS, Mobilize Boston Comprehensive neuropsychological test Consortium to Establish a Registry for Alzheimer’s Disease (CERAD) battery battery • SALIA
Prevalence studies – assessment of exposure Residential distance to a busy street <=50m, 50- 100, >100m (SALIA) Black carbon PM10 (NAS & (SALIA) MOBILIZE Exposure Boston) Residential Chinese Air distance to Pollution a major Index roadway (CLHLS 3 rd and 3 rd & 4 th waves) (MOBILIZE Boston)
Air Pollution, prevalence studies, results, NAS • doubling of BC exposure over the previous year - MMSE <26 OR1.3 (1.1:1.6). CLHLS • a point increase in API - MMSE <18 OR1.09 (1.01:1.18) and worsening MMSE by 0.52 points (0.27:0.75). MOBILIZE Boston • living nearer to a busy road (per 851.2m) - MMSE <26 only in those with • a College education OR1.54 (1.10:2.17) • or aged ≤77 years OR1.34 (1.01:1.76). For BC (for a 0.11µg/m 3 greater exposure during the preceding yr) MMSE <26 • OR1.15(0.99:1.34) SALIA • traffic and PM 10 exposure over five years - worse cognitive performance on the CERAD battery and Stroop test. NHANES III • greater exposure to PM 10 (per 10µg/m3) or ozone (per 10ppb) over the preceding year - poorer cognitive performance on all tests except simple reaction time
Air pollution – incidence studies Follow Cognitive Measure of exposure to air Study N up assessment Outcome pollution Meteorological and Geographic Information System (GIS) data for each geocoded residential location Composite for PM 10 , PM 2.5 . PM 2.5-10 TICs measures calculated from difference. Nurses’ Assessed (validated of cognition Averaged exposure over Health 19409 at 1.9 and telephone via z 1988, 1 month, 1 year, 2 years Study females 4.3 years interview) scores and 5 years before first test Environmental Protection Agency air quality ground level monitoring stations and aerosol optical depth data from Baseline Score <=4 satellites combined to provide 20,150 then classified 1 year mean exposure PM2.5 RE- males annual 6 item as incident per participant using an GARDS and telephone telephone cognitive algorithm up to and including Study females contact assessment impairment the date of the baseline visit
Air pollution – incidence studies, results Study Outcome Z score change per 10 µg/m 3 increase in PM 2.5 , preceding month -0.002 (-0.016:0.012) preceding year -0.016 (-0.034:0.003) Nurses’ Health Study preceding 2 years -0.015 (-0.034:0.003) preceding 5 years -0.020 (-0.038:0.002) since 1988 -0.018 (-0.035:-0.002) By 10 µg/m 3 increase in PM 2.5 . Logistic regression for incident cognitive REGARDS Study impairment; OR0.98 (0.72-1.34)
More recent work… Incident cognitive decline • Tonne et al 2014 Longitudinal Whitehall II cohort, London UK. • N=2767 Males and females • 5 year follow up Incident dementia • Oudin et al 2015 Longitudinal Betula study, Umea, Sweden • N=1806 Males and females • 15 year follow up
Whitehall cohort • Air pollution assessed between 2003-2009 • Cognitive function assessed 2002-2004 and 2007-2009 • Neuropsychological battery
The authors conclude ‘This study provides support for an association between particulate air pollution and some measures of cognitive function as well as decline over time in cognition’
Betula study • Air pollution assessed 2009-2010, • Sensitivity analysis with air pollution back extrapolated to levels more likely at study start 1993-1995 • Measured nitrogen oxide The authors conclude, ‘If the associations we observed are causal, then air pollution from traffic might be an important risk factor for vascular dementia and Alzheimer’s disease’ • Dementia assessed at baseline 1993-1995 and every 5 years. • Incident cases identified using the DSM-IV supplemented by medical data and imaging where available
Limitations • Different populations • Different assessments of exposure to pollutants • Different assessment of outcome • Many possible confounders not addressed/adjusted for eg exposure to in home wood-smoke etc: • Most studies cross sectional • Timing of exposure and assessments not clear in many reports • Very little longitudinal data where exposure occurred before outcome! • Impossible to aggregate data • Impossible to infer clinically or environmentally relevant outcomes
Conclusions • Air pollution may contribute to dementia risk but nothing can be concluded from the existing evidence base. • More robust studies are needed.
Thank you, Questions?
Recommend
More recommend
