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SYNOPSIS: The authors of a review and meta-analysis involving four studies and more than 5,000 community-dwelling adults over the age of 60 years concluded that greater adherence to the Mediterranean diet was associated with a reduced risk of frailty.
SOURCE: Kojima G, Avgerinou C, Iliffe S, Walters K. Adherence to Mediterranean diet reduces incident frailty risk: Systematic review and meta-analysis. J Am Geriatr Soc 2018; Jan. 11. doi:10.1111/jgs.15251.[Epub ahead of print].
Currently, the only available alternative to aging is death. However, development of frailty linked with aging may not be so inevitable. In fact, evidence is building that the onset of frailty, theoretically defined in 2011 as “a clinically recognizable state of increased vulnerability resulting from aging-associated decline in reserve and function across multiple physiologic systems,” has modifiable risk factors.1
Nutritional status is believed to play an important role in either development or protection from frailty.2 However, it is not known if a specific diet or dietary pattern is key. Kojima et al noted that studies regarding the Mediterranean diet and frailty are few in number and have produced mixed results. They believed a meta-analysis could assist in revealing more subtle relationships. After performing a systematic and extensive literature search, Kojima et al identified four studies meeting all criteria to include in the meta-analysis. These studies included 5,789 community-dwelling people ≥ 60 years of age. The mean follow-up time was 3.9 years. The included studies used the Mediterranean Diet Score (MDS)3 to measure the degree of adherence to a traditional Mediterranean diet. Based on their scores on the MDS, respondents were grouped into one of three possible categories (0-3; 4-5; 6-9), with higher scores representing closer adherence to the diet. Each study used a food frequency questionnaire to record dietary choices.
To measure frailty, researchers used one of two standardized scoring tools. Both scales incorporated multiple criteria to assess degree of frailty. All four studies used odds ratios (OR) adjusted for multiple variables to represent the incident frailty risk.
Three studies were conducted in Southern Europe or Mediterranean Europe, and one study was from China. Notably, dietary patterns from the Mediterranean region are the foundation of the Mediterranean diet. Kojima et al wondered if the Chinese study, given the difference in native dietary habits, was skewing results. However, excluding the Chinese study did not change results substantially.
Table 1 shows the incident frailty risk in the pooled group of four studies when comparing higher adherents to the Mediterranean diet with lower adherents. The second portion of the chart shows incident frailty risk in the reduced pooled group to just the three studies performed in Mediterranean Europe (Chinese study excluded.) All ORs are adjusted for multiple variables or potential confounders, including sex and age of participants, marital status, use of medication, and health habits, such as use of tobacco products and/or alcohol.
The authors of this large meta-analysis looked at the results of four studies investigating adherence to the Mediterranean diet and frailty. A review of these terms — Mediterranean diet and frailty — may clarify the results and implications of the study.
The Mediterranean diet takes its name from its origins in lands surrounding the Mediterranean Sea. Well-known for many potential health benefits, the Mediterranean diet is not a diet per se but a pattern of eating based on the traditional diet of this geographic region. Plant foods, such as vegetables, fruits, nuts, legumes, and seeds, are the base of the diet, with olive oil the primary source of fat. Dairy is limited and usually in the form of cheese and/or yogurt. Typically, fish is the most prominent animal food, followed by poultry and occasional red meat. Wine consumption is moderate and usually accompanies a meal.4
In all the studies in the meta-analysis, food consumption records were obtained via food frequency questionnaires. It is worth noting that the accuracy of these reports was determined in large part by memory and truthfulness of the participants. Future studies with more objective methods will be helpful in reaching a fuller understanding of the relationship between diet and frailty.
Frailty is a medical concept lacking a standard definition, but theoretically understood as a common geriatric syndrome with increasing prevalence with age. In 2001, Fried et al offered descriptive criteria now commonly accepted for use as a working definition to enhance the understanding of frailty. They identified five benchmarks: unintentional weight loss, exhaustion, deterioration in grip strength, slowed gait, and decreased physical activity. According to the Fried definition, three out of the five criteria must be present to diagnose and stage frailty. Thus, frailty is distinct from comorbidities and disability rather than synonymous with these conditions, as had been postulated up until Fried’s work. In fact, we now understand that disability may result from frailty and that comorbidities contribute to this condition.5
A working operational definition allows systematic investigation of frailty risk factors and outcomes. Frailty itself is a risk factor for many poor health outcomes, including complications in hospitalized patients, earlier death, and poorer quality of life. Although the etiology, development, and progression of frailty appear to be complex and multifaceted, studies looking at improving nutritional state consistently are promising. Researchers have studied enhancing protein status and micronutrient load (carotenoids and vitamins).6
Although frailty may seem similar to failure to thrive (FTT), frailty is better understood as a contributor to this potentially more fulminant condition. FTT, defined as a “syndrome of weight loss, decreased appetite and poor nutrition, and inactivity, often accompanied by dehydration, depressive symptoms, impaired immune function, and low cholesterol” resides further along a spectrum that may result in full dependence and/or death.7
Estimates of prevalence of frailty vary according to population (institutionalized vs. community-dwelling, for example) and gender. Conservative estimates are that frailty affects about 10% of persons ≥ 65 years of age (15% of those 80 to 85 years of age and 26% of those > 85 years of age). Given these numbers, understanding and identifying prevention factors could affect public health costs significantly.8
The investigations included in this meta-analysis all attempted to go beyond looking at a specific food item or nutrient and focused instead on total intake or dietary pattern. While this makes sense intuitively given what we know about the interplay of micro- and macronutrients, it makes interpreting the results for clinical use a bit more challenging. Although we can tell patients that following a Mediterranean diet is associated with a lower risk of frailty, these studies do not allow an understanding of which elements of this diet are most crucial to protection. Kojima et al postulated that the antioxidant load in the abundant fruits and vegetables at the heart of the Mediterranean diet may be a key factor in defeating frailty development. Clearly, future studies elucidating this most likely multifactorial relationship are essential.
Kojima et al met their goal of performing a meta-analysis to better understand the relationship between adherence to the Mediterranean diet and development of frailty. Incorporating multiple studies allows sufficient numbers of participants to interpret results with confidence, at least for the included populations. The results are impressive and show a close to linear reduction of frailty risk with higher adherence to a Mediterranean diet. Presenting these results in graphic form may serve as “food for thought” for older patients looking for dietary guidance.
One limitation of this meta-analysis is that only four studies were included. Although numbers of total participants are high, having few studies makes generalization of the results to all geographic and ethnic populations difficult. Cultural beliefs and food availability influence dietary patterns. The inclusion of a Chinese study in the meta-analysis is impressive in that in lends confidence that these results may be transferable across cultural barriers. However, incorporating many cultures and backgrounds will be important to present these results with full confidence.
Another interesting aspect of these studies is that diet information was collected at the onset of the investigations when (by definition) all participants were ≥ 60 years of age. We do not have information about dietary habits prior to this age. A long-standing dietary pattern may be influential on frailty development, but we are not able to conclude or extrapolate from the provided information.
Certainly, for now, explaining the highlights of a Mediterranean diet to patients at risk for development of frailty falls squarely into the category of good preventive medicine. Notably, this risk pool includes all patients > 60 years of age. A Mediterranean diet pyramid for distribution in the office is a readily available tool for review of diet components.8 Finally, explaining to patients that there is no evidence of an “all or none” phenomenon with this eating pattern should be reassuring. Informing patients that a shift toward greater adherence to this dietary pattern may be associated with maintaining strength while aging can be instrumental in helping the patient view a change in dietary habits as possible rather than formidable.
Financial Disclosure: Integrative Medicine Alert’s Executive Editor David Kiefer, MD; Peer Reviewer Suhani Bora, MD; AHC Media Executive Editor Leslie Coplin; Editor Jonathan Springston; and Editorial Group Manager Terrey L. Hatcher report no financial relationships relevant to this field of study.