Air pollution amplifies dementia risk in cardiometabolic disease patients – healthy habits can help

New research shows how simple lifestyle changes can mitigate the dual threat of cardiometabolic disease and air pollution on cognitive health.

Study: Association between air pollution and lifestyle with the risk of developing mild cognitive impairment and dementia in individuals with cardiometabolic diseases. Image credits: NDAB Creativity / Shutterstock

This is evident from a recent study published in the journal Scientific reportsresearchers examined the risk of mild cognitive impairment (MCI) and dementia in patients with cardiometabolic diseases (CMD). They found that CMD patients, compared to healthy ‘normal’ individuals, had a significantly higher risk of MCI and dementia.

Patients with three CMDs had the highest risk, with an HR of 1.951 for MCI, 1.554 for all-cause dementia, 1.216 for Alzheimer’s disease, and 2.032 for vascular dementia. Higher concurrent CMD counts were associated with greater odds of MCI and dementia.

Air pollution exacerbated these effects, with pollutants such as PM2.5, NO2 and NOX having a particularly significant impact. However, a healthy lifestyle reduced the strength of these associations.

Together, the current study suggests that maintaining a healthy lifestyle is critical for preventing MCI and the onset of dementia. Because both conditions are lifelong and have no cure, these findings can help provide physicians, healthcare providers, and CMD patients with the information needed to combat the rising prevalence of these debilitating diseases.

Background

‘Dementia’ is the umbrella term for identifying diseases that affect individuals’ memory, language and other thinking abilities that are essential for daily activities. It is a severely debilitating condition known to alter patients’ personality, moods and behaviors. Unfortunately, no cure for dementia has yet been discovered, making prevention the priority of current research into the condition.

Alarmingly, the prevalence of dementia worldwide is increasing at an unprecedented rate, by 117% in just over two decades (1990-2016). Current estimates show that more than 57 million people are living with dementia, with expected economic losses of more than $1,313 billion.

Research hypothesizes that while genetics plays an important role in dementia prevalence, the global aging population, suboptimal lifestyle choices and increased pollution levels may worsen the risk of dementia.

Clinical studies have demonstrated the link between cardiometabolic diseases (CMDs; for example, diabetes mellitus type 2). [T2DM]coronary heart disease [CHD]and stroke) and dementia, with the former nearly doubling the risk of the latter occurring. Similar associations between CMDs and mild cognitive impairment (MCIs) have been independently documented.

Notably, individuals with two or three CMD diagnoses were found to have significantly higher risks, with HRs for vascular dementia increasing to 6.632 in those with all three CMDs. However, the cumulative effects of multiple CMDs, air pollution levels, and lifestyle remain unknown.

About the study

The present study aimed to unravel the simultaneous impact of ambient air pollution and lifestyle scores on dementia/MCI risk in CMD patients. Study data were obtained from the United Kingdom (UK) Biobank, a comprehensive biomedical database of more than 500,000 UK-based adults (ages 39–74 years). Of the 502,370 participants screened for the study, 63,689 presented incomplete sociodemographic, lifestyle, and medical information and were excluded from subsequent analyses.

UK Biobank medical history data were used to assess the number and severity of CMDs within the study cohort. The same datasets also included MCI and dementia diagnoses, with a follow-up period of ~15.12 years. Exposure to air pollutants, such as PM2.5, PM10 and NO2, was estimated using land use regression (LUR) models.

Structured baseline questionnaires were used to evaluate participants’ healthy lifestyle scores. These questionnaires consisted of seven items, including 1. diet, 2. alcohol consumption, 3. smoking status, 4. physical activity levels, 5. sedentary behavior, 6. social relationships, and 7. sleep patterns.

Statistical analyzes included latent class analysis (LCA) for the identification of air pollutant patterns, Cox proportional regression models for dementia/MCI risk assessments and sensitivity analyses.

Study findings

Of the 438,681 participants included in the analyses, 17.11% (n = 75,056) were diagnosed with CMD. Of these, 15.12% suffered from one CMD, 1.90% suffered from two simultaneous CMDs and 0.09% suffered from three CMDs. Statistical analyzes showed that ambient air pollution and poor lifestyle independently contributed to the prevalence of dementia/MCI, with dementia/MCI patients generally showing poorer lifestyle choices and higher air pollution exposure than their ‘normal’ counterparts.

“The risk of developing mild cognitive impairment, all-cause dementia, Alzheimer’s disease, and vascular dementia in patients with CMDs was 1.951, 1.554, 1.216, and 2.032 times higher, respectively, than in those without CMD.”

CMD was found to significantly increase the risk of dementia and MCI by between 121 and 203%. The number of concurrent CMDs appeared to worsen these outcomes: patients with two or three CMD diagnoses were significantly more likely to develop MCI or dementia than patients with only one CMD.

When analyzed together, air pollutants such as PM2.5 and NO2 consistently increase the risk of dementia and MCI. Lifestyle behaviors (easily modifiable) attenuated the impact of air pollution, indicating a protective effect of these behaviors on the future incidence of dementia/MCI.

Conclusions

The current study is the first to evaluate the associations between CMD (presence and number of concurrent diagnoses) with MCI and dementia risk, while simultaneously examining the impact of ambient air pollution and lifestyle choices on MCI/dementia outcomes. It highlights the cumulatively escalating risk of dementia/MCI in CMD patients, which increases directly with the number of concurrent CMD diagnoses.

Patients exposed to high levels of pollution but following healthier lifestyle behaviors showed lower risks, highlighting the modifiable nature of lifestyle factors.

Although both air quality and lifestyle scores were found to influence MCI/dementia risk outcomes, the latter are easily modifiable and can be used to protect against the onset of MCI/dementia.