As the world’s population gets older, understanding the factors that influence healthy aging has become incredibly important. One of the major challenges we face globally is the rising number of people affected by dementia. In 2019, there were an estimated 55 million people living with dementia, with projections showing this could rise dramatically to 139 million by 2050. Low- and middle-income countries bear a significant portion of this burden, and understanding the unique factors in these regions is crucial.
We know that things like our genes, chronic health conditions (like diabetes or high blood pressure), and even psychological factors can impact our cognitive health as we age. In Brazil, specifically, research has pointed to low education, hypertension, and hearing loss as key risk factors for dementia.
Another factor often discussed in the context of aging is physical frailty. You might have heard this term used to describe someone who seems a bit delicate or has less resilience. In research, frailty is often defined as having a lower capacity to cope with stressors. It’s a state linked to increased vulnerability, and previous studies elsewhere in the world have suggested it might be a risk factor for cognitive impairment and dementia. For instance, a large study in the UK found that frailty was associated with a higher risk of developing dementia over 8 years, even independently of genetic risk.
Given this background, researchers in Brazil embarked on a study called FIBRA (Frailty in Brazilian Older Adults) to delve deeper into these relationships within their own population. The FIBRA study initially looked at how frailty was associated with physical and psychological health, including cognition, in older adults aged 65 and over. After nine years, they conducted a follow-up to see how things had changed. The specific goal of this follow-up study was to investigate if physical frailty measured at the start of the study increased the risk of a decline in overall cognitive function and the ability to perform daily activities after those nine years.
What Did the Study Involve?
The FIBRA study followed older adults living at home in specific areas of Campinas and São Paulo, Brazil. They started with 1284 participants at the beginning (2008-2009). To focus on predicting new deficits, they excluded 98 participants who already showed signs of cognitive impairment at the start.
Nine years later (in 2016-2017), the researchers managed to locate and re-interview 451 of the original participants who met the inclusion criteria. It’s worth noting that, as is common in long-term studies, many participants were lost to follow-up over the nine years, either due to death (14.9%) or other reasons like moving or refusing to participate (42.4%).
The follow-up group of 451 participants mostly consisted of women (68.1%), people aged 65-74 (71.6%), and those with a lower level of education (0-4 years, 75.6%). At the start of the study, most participants were classified as non-frail (35.5%) or pre-frail (57.0%), with a smaller percentage being frail (7.5%). By the nine-year follow-up, 85 participants scored below the cut-off on a common cognitive test (the Mini-Mental State Exam, or MMSE), indicating a potential cognitive deficit. Of these 85, 45 also showed difficulties with functional activities, meaning they had cognitive and functional deficits.
To measure cognition, the study used the Mini-Mental State Examination (MMSE), which gives a score out of 30. Lower scores suggest cognitive decline, with specific cut-off points used based on education level. Functional ability was assessed using the Functional Activity Questionnaire (FAQ), which looks at performance in daily tasks like managing finances or preparing meals. A FAQ score of 5 or higher was considered indicative of functional limitation.
Frailty was measured at the beginning of the study using a well-known method called the frailty phenotype. This involves assessing five key components:
- Unintentional weight loss (losing 4.5 kg or 5% of body weight in the past year).
- Fatigue (feeling tired always or almost always based on specific questions).
- Low hand-grip strength (below a certain threshold adjusted for sex and body size).
- Slow gait speed (taking longer than a certain time to walk a short distance, adjusted for sex and height).
- Low physical activity level (spending less energy on weekly activities compared to peers).
Based on how many of these criteria a participant met, they were classified as non-frail (0 criteria), pre-frail (1 or 2 criteria), or frail (3 or more criteria).
The Surprising Finding
The researchers used statistical methods, including logistic regression, to see which factors at the start of the study predicted the likelihood of having cognitive and functional deficits nine years later. They specifically looked at frailty status while also accounting for age, sex, and education.
Previous studies from Europe, Asia, and North America, including a large systematic review, had found significant associations between frailty and a higher risk of cognitive problems or dementia over time. These studies suggested that frail older adults were indeed at greater risk. Some studies even found that frailty predicted dementia risk independently of genetic risk or mediated the relationship between healthy lifestyle and dementia risk.
However, the results of this specific study in Brazil provided a contrast. The main finding was that physical frailty at the start of the study was not associated with having cognitive and functional impairment nine years later. In the statistical model, neither being pre-frail nor frail at baseline significantly increased the odds of experiencing cognitive and functional deficits at follow-up compared to being non-frail.
What Did Predict Decline?
While frailty didn’t show a predictive link in this study, other factors did. The analysis revealed that older age at baseline was significantly associated with a higher risk of cognitive and functional impairment after nine years. This finding aligns with extensive research worldwide, which consistently shows that increasing age is a major risk factor for dementia. In this study, participants aged 70-74 and those aged 75 and over at the start were significantly more likely to have cognitive and functional deficits nine years later compared to those aged 65-69.
Another strong predictor found in this study was lower education level at baseline. Participants with more years of education at the start of the study had a lower risk of developing cognitive and functional deficits. Specifically, having 5 or more years of education significantly reduced the odds of impairment compared to having no formal schooling. This supports findings from other longitudinal studies in Brazil and elsewhere that have linked lower educational attainment to a higher incidence of dementia.
Education is often seen as a proxy measure for cognitive reserve. This concept suggests that a stronger cognitive reserve—built through education, challenging jobs, and engaging activities—can help the brain cope better with aging and disease, potentially delaying the appearance of cognitive and functional problems even if underlying brain changes are present. Higher education consistently appears as a protective factor against cognitive impairment in research.
Interestingly, other factors like sex, number of chronic diseases, tobacco use, and alcohol use were also analyzed but did not show a significant association with cognitive and functional deficits in this specific study’s primary logistic regression model.
Why the Different Findings?
The study authors discussed why their results regarding frailty might differ from many international studies that did find frailty to be a predictor of dementia. They suggest that differences might exist due to variations in the study populations or the methods used.
They also highlighted that some previous studies have shown similar nuances. For example, one study found the link between frailty and dementia only remained significant after adjusting for some factors, but not in a model that included a wider range of risk factors like cardiovascular health or previous cognitive function. Another study suggested frailty might reflect underlying brain conditions rather than being an independent predictor of the progression from mild cognitive impairment (MCI) to dementia. Some research even indicated that frailty might only predict dementia in individuals with higher cognitive function at the start, not those already performing at a lower level.
The authors also pointed out limitations in their own study. The relatively small number of participants available for the 9-year follow-up is a factor, potentially making the sample less representative. Another limitation was the way cognitive and functional deficits were assessed – using screening questionnaires (MMSE and FAQ) rather than a full clinical diagnosis of dementia involving comprehensive tests, lab work, and brain imaging. This lack of a clinical diagnosis might partially explain why frailty wasn’t found to be a predictor in this instance. Additionally, the MMSE might not detect milder forms of cognitive impairment like MCI, and the FAQ relies on a family member or informant’s report, which could introduce bias.
What’s the Takeaway?
For this specific group of older adults in Brazil followed over nine years, frailty at the beginning of the study did not appear to be a significant predictor of developing cognitive and functional deficits.
Instead, the study reinforced the well-established importance of age and highlighted the protective effect of education as key factors influencing cognitive and functional outcomes over time. Higher age and lower education at the start of the study significantly increased the likelihood of experiencing these declines.
The study’s findings underscore that while frailty is an important aspect of aging, its relationship with cognitive decline might be complex and potentially influenced by population characteristics and how cognitive/functional issues are defined and measured.
The researchers conclude by emphasizing the need for more longitudinal studies in low- and middle-income countries to further explore and clarify the factors that predict cognitive and functional decline. This research is vital to help develop effective strategies for preventing or delaying these challenges in older populations worldwide. Despite its limitations, this study’s longitudinal design and the adequate follow-up time provide valuable insights into aging in the Brazilian context.
Study source full report can be found here.