Could a healthy lifestyle delay cognitive decline?

Individuals with familial dementia (FD), defined as dementia in a first-degree relative, which confers an increased risk of dementia, could reduce their risk by adopting a healthy lifestyle, a study presented at the American Heart Association (AHA) Epidemiology, Prevention, Lifestyle & Cardiometabolic Health Conference 2021 showed.

“Adopting more healthy behaviours was associated with reduced risk of dementia, independent of FD. In those with FD, adopting at least three healthy behaviours may help reduce the risk of developing dementia,” noted study author Assistant Professor Angelique Brellenthin from Iowa State University, Ames, Iowa, US, and colleagues.

“This study provides important evidence that a healthy lifestyle can have a positive impact on brain health,” added AHA President, Professor Mitchell Elkind, who was not affiliated with the study.

The researchers analysed 302,239 individuals aged 50–73 years who were enrolled in the UK Biobank Study and who completed a baseline examination in 2006–2010. Individuals with dementia at baseline were excluded. Information on family history and lifestyle factors was ascertained through questionnaires.

Six healthy behaviours were identified: not obese (BMI <30 kg/m²); physically active (≥150 minutes/week of moderate-to-vigorous physical activity); sleep duration of 6–9 hours; moderate alcohol consumption (>0 to ≤14 or seven drinks/week for men and women, respectively); not smoking; and a healthy diet (eg, more fruits and vegetables, less processed meats and refined grains). One point was given for each of the healthy behaviours, and participants were categorized as following ≤2, three, four, five, or six healthy behaviours.

Participants were followed up for a mean 8 years, during which time 1,698 individuals (0.6 percent) developed dementia.

After adjusting for confounders* and healthy behaviours, individuals with FD had a higher risk of incident dementia than those without a history of FD (adjusted hazard ratio [adjHR], 1.72, 95 percent confidence interval [CI], 1.53–1.93). [EPI 2021, Presentation 74]

After adjusting for the confounders and FD, the risk of incident dementia was reduced among individuals who followed a higher number of healthy behaviours.

There was a 30-percent reduced risk of dementia among participants with three vs ≤2 healthy behaviours (adjHR, 0.70, 95 percent CI, 0.57–0.86), a 42-percent reduced risk among those with four or five healthy behaviours (adjHR, 0.58, 95 percent CI, 0.48–0.70 for each vs ≤2 healthy behaviours), and a 51-percent reduced risk among those with six healthy behaviours (adjHR, 0.49, 95 percent CI, 0.39–0.60).

Compared with individuals with FD who followed ≤2 healthy behaviours, the risk of dementia was reduced among those with FD who followed ≥3 healthy behaviours (adjHR, 0.65, 95 percent CI, 0.42–0.99), with a more marked reduction observed among those without FD who followed ≥3 healthy behaviours (adjHR, 0.37, 95 percent CI, 0.25–0.56).

There was also a reduced risk observed among individuals with no FD with ≤2 healthy behaviours compared with those with FD and ≤2 healthy behaviours (adjHR, 0.74, 95 percent CI, 0.47–1.15).

A somewhat unexpected finding was the higher level of healthy behaviours among individuals with FD. “[P]articipants who followed more of the healthy behaviours at baseline also reported more FD at baseline,” Brellenthin pointed out. “For example, there was an 11-percent prevalence of FD among those following ≤2 healthy behaviours, compared to 15-percent prevalence of FD among those following all six healthy lifestyle behaviours. And individuals who followed more healthy behaviours were less likely to develop dementia in general,” she said.

“FD is one of the strongest risk factors for dementia. [However,] little is known about the independent and combined associations of having FD and following a healthy lifestyle with the risk of dementia,” said Brellenthin and co-authors.

“When dementia runs in a family, both genetics and non-genetic factors, such as dietary patterns, physical activity, and smoking status, affect an individual’s overall risk,” she continued. “This means there may be opportunities for reducing risk by addressing those non-genetic factors.”

The authors acknowledged that the findings do not infer causation. Furthermore, FD status was acquired through questionnaires and not genetic testing. 

“[Nonetheless,] it should be reassuring and inspiring [for] people to know that following just a few healthy behaviours can delay cognitive decline, prevent dementia, and preserve brain health,” said Elkind.