The Link Between Smoking and Cognitive Decline

By now, you are likely aware of many of the well-established risks associated with smoking cigarettes, such as cancer, asthma, chronic obstructive pulmonary disease (COPD), diabetes, cardiovascular disease, and stroke. But did you know that research has discovered a link between smoking and cognitive decline?

This research emphasizes the importance of identifying and controlling modifiable risk factors for cognitive decline and dementia as early as possible while monitoring brain health to detect changes in brain function as early as possible.

Here is everything you need to know about smoking and cognitive decline, including a breakdown of the research and the best way to monitor brain health while controlling modifiable risk factors for dementia.

Smoking, Cognitive Decline, and Dementia Risk: A Breakdown of the Research

Over the past two and a half decades, researchers have discovered a significant connection between smoking, cognitive decline, and dementia. Research suggests smoking increases the risk of cognitive decline and dementia and may accelerate cognitive decline in individuals with Mild Cognitive Impairment.

Smoking and Cognitive Decline

A 2008 study assessing smoking and cognitive decline among middle-aged men and women found that at baseline, people who smoke scored lower than those who have never smoked in global cognitive function, speed, and flexibility. At the five-year follow-up, decline among smokers was 1.9 times greater for memory function, 2.4 times greater for cognitive flexibility, and 1.7 times greater for global cognitive function compared to those who have never smoked. Additionally, smokers who smoked a greater number of cigarettes (measured in pack-years) showed a greater decline in cognitive function.

A 2012 study assessing the impact of smoking on cognitive decline in early old age found that middle-aged male smokers experienced faster cognitive decline when compared to those who have never smoked. In former smokers (with at least a 10-year cessation), no adverse effects on cognitive decline were observed. They also found that cognitive decline did not vary as a function of smoking status in women, though several other studies have produced contradictory findings. For example, a 2021 study found that smoking was associated with impaired verbal learning and memory performance in women more than men. 

A 2021 study found that among people with Mild Cognitive Impairment, smokers showed a more rapid decline in functional performance compared to non-smokers, where functional performance refers to the ability to complete Activities of Daily Living (normal day-to-day activities).

Together, this research suggests that there is indeed a relationship between smoking and cognitive decline, though it is not yet clear what role sex plays in this relationship.

Smoking and Dementia Risk

Over the years, many studies have assessed the impact of smoking on the risk of developing dementia later in life. A review of 37 research studies assessing the association between smoking, dementia risk, and Alzheimer’s disease risk found that when compared to people who have never smoked, current smokers are 30% more likely to develop dementia and 40% more likely to develop Alzheimer’s disease, the leading cause of dementia. They also concluded that smoking cessation can reduce the risk of developing dementia.

To summarize all of the above research and make this a bit more digestible, here is what research currently suggests:

• Smoking in midlife is associated with a decline in cognitive and functional aspects of brain health, particularly in domains of cognitive function such as learning and memory and executive function.
• Smoking is associated with an increased risk of developing dementia as well as Alzheimer’s disease.
• Heavy smoking is associated with greater cognitive decline.
• Smoking cessation can reduce the risk of developing dementia.

Why is Smoking Associated with Cognitive Decline and Dementia?

While there is a clear connection between smoking and cognitive decline, it is not fully clear why it is that smoking affects brain health. However, there are several theories on how smoking damages our brains and increases the risk of developing dementia, including the following:

• Smoking may accelerate brain aging.
• Smoking may increase the risk of developing Alzheimer’s disease by increasing oxidative stress.
• Vascular conditions, such as stroke and heart disease, as well as risk factors for vascular conditions, such as high blood pressure, high cholesterol, and type 2 diabetes, have all been linked to an increased risk of dementia. As smoking can cause damage to the brain and blood vessels, it can cause vascular conditions and consequently increase dementia risk.
• Smokers are at high risk for insomnia and sleep apnea, conditions which have been linked to an increased risk of developing dementia.

Controlling Modifiable Risk Factors and Monitoring Brain Health

The connection between smoking and cognitive decline has important implications for individuals who smoke. While smoking is a tough habit to quit, it is a modifiable risk factor for dementia. By taking appropriate steps to control risk factors and regularly monitoring brain health, patients can benefit from early intervention and better health outcomes. In the event a decline in brain function is detected, frequent and consistent monitoring of brain health provides early diagnosis and early treatment.