A recent study conducted by researchers using data from the Neurological Disorders in Central Spain (NEDICES) cohort study has provided evidence that cumulative smoking exposure is associated with cognitive decline in older adults. The study aimed to address the inconclusive results regarding the relationship between smoking exposure and cognitive decline among older adults. The findings were published in Scientific Reports.
Dementia, the seventh leading cause of death globally, remains a major cause of long-term disability and dependency. Vascular diseases are well-established risk factors for dementia in older adults, and smoking exposure is a potent risk factor for vascular diseases, including stroke. While some studies have shown a consistent association between current smoking status and dementia, the relationship between smoking exposure and cognitive decline remains inconclusive.
The NEDICES cohort study involved 2,624 older adults (≥ 65 years) who were prospectively evaluated at two time-points separated by three years. Researchers used a 37-item version of the Mini-Mental State Examination (MMSE-37) to assess cognitive change in the participants. Smoking exposure was calculated based on pack-years (packs of cigarettes smoked per day multiplied by years of smoking) for current and former smokers.
After adjusting for several demographic and clinical variables, the MMSE-37 total score showed a decline in all tertiles of pack-years (low, medium, and high) compared to never-smokers. A decline was also observed in both current and former smokers compared to never smokers. These findings support the hypothesis that the higher the exposure to smoking among non-demented older adults, the higher the cognitive decline.
The exact mechanisms behind the association between smoking and cognitive decline remain unclear. Chronic smoking is known to be associated with cerebral small vessel disease burden, white matter degeneration, and an increased risk of cognitive decline. Furthermore, chronic smoking exposure has been linked to accelerated brain ageing.
The study has some limitations, such as the exclusion of a large number of participants due to missing data and the fact that the study only included Spanish participants. Additionally, the MMSE-37 is a relatively abbreviated dementia screening tool, and more formal neuropsychological testing is needed in future studies. The presence of minor neurocognitive disorders was also not considered in the analyses, and some potential confounding factors were not adjusted for.
Despite these limitations, the study has several strengths, including its population-based design, the standardized prospective assessments, and the adjustment for potential confounding effects of several key factors.
The study provides valuable evidence of the cumulative effect of smoking on cognition in older adults, highlighting the association between cumulative smoking exposure and cognitive decline in non-demented older adults. Further population-based research is necessary to clarify this association in older adults without dementia, which could lead to better prevention strategies and improved public health outcomes.
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