CLINICAL INVESTIGATIONS
Animal Protein Intake Is Associated with Higher-Level Functional Capacity in Elderly Adults: The Ohasama Study Eri Imai, PhD, RD,a Megumi Tsubota-Utsugi, PhD, MPH, RD,a Masahiro Kikuya, MD, PhD,b Michihiro Satoh, MSc,c Ryuske Inoue, MD, PhD,d Miki Hosaka, MSc,c Hirohito Metoki, MD, PhD,b Naomi Fukushima, MSc,e Ayumi Kurimoto, MSc,f Takuo Hirose, PhD,g Kei Asayama, MD, PhD,h Yutaka Imai, MD, PhD,c and Takayoshi Ohkubo, MD, PhDc,i
OBJECTIVES: To determine the association between protein intake and risk of higher-level functional decline in older community-dwelling adults. DESIGN: Prospective. SETTING: Ohasama Town, Japan. PARTICIPANTS: Residents (N = 1,007; mean age 67.4 5.5) free of functional decline at baseline; follow-up was conducted for 7 years. MEASUREMENTS: Nutrient and food intakes were determined using a validated 141-item food frequency questionnaire. Participants were divided into quartiles according to intake levels of total, animal, and plant protein. Subscales of the Tokyo Metropolitan Institute of Gerontology Index of Competence subscales were used to assess higher-level functional decline. Logistic regression analysis was used to examine the future risk of higher-level functional decline in relation to protein intake, with lowest protein intake as reference. RESULTS: During the study period, 24.4% of eligible participants reported declines in higher-level functional
From the aSection of the Dietary Reference Intakes, Department of Nutritional Epidemiology, National Institute of Health and Nutrition, Tokyo, Japan; bTohoku Medical Megabank Organization, Tohoku University, Sendai, Japan; cDepartment of Planning for Drug Development and Clinical Evaluation, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan; dDepartment of Medical Informatics, Graduate School of Medicine, Tohoku University, Sendai, Japan; eDivision of Community Health Nursing, School of Nursing, Fukushima Medical University, Fukushima, Japan; fDivision of Community Health Nursing, School of Health Sciences, Faculty of Medicine, Tohoku University, Sendai, Japan; gCenter for Interdisciplinary Research in Biology, College de France, Paris, France; hStudies Coordinating Centre, Division of Hypertension and Cardiovascular Rehabilitation, Department of Cardiovascular Diseases, University of Leuven, Leuven, Belgium; and i Department of Hygiene and Public Health, School of Medicine, Teikyo University, Tokyo, Japan. Address correspondence to Megumi Tsubota-Utsugi, Section of the Dietary Reference Intakes, Department of Nutritional Epidemiology, National Institute of Health and Nutrition, Toyama 1–23–1, Shinjyuku-ku, Tokyo 162–8636, Japan. E-mail: [email protected] DOI: 10.1111/jgs.12690
JAGS 2014 © 2014, Copyright the Authors Journal compilation © 2014, The American Geriatrics Society
capacity. After adjustment for putative confounding factors, men in the highest quartile of animal protein intake had significantly lower risk of higher-level functional decline than those in the lowest quartile (odds ratio (OR) = 0.41, 95% confidence interval (CI) = 0.20–0.83; P for trend .01). These associations were not seen in women (OR = 0.76, 95% CI = 0.41–1.34; P for trend .37). No consistent association was observed between plant protein intake and future higher-level functional decline in either sex. CONCLUSION: Higher protein, particularly animal protein, was associated with lower risk of decline in higherlevel functional capacity in older men. Animal protein intake may be a modifiable indicator for early detection and prevention of higher-level functional decline in elderly adults. J Am Geriatr Soc 2014.
Key words: animal protein; plant protein; functional capacity; healthy community dwelling; Japanese
W
ith the rapidly increasing life expectancy of the Japanese population, the percentage of individuals aged 65 and older has increased from 10.3% in 1985 to 20.1% in 2005.1 Collaterally, there has been a noticeable increase in the number of elderly people living with functional decline. Functional decline is now thought to have an enormous effect on hospitalization, institutionalization, and death and leads to adverse effects on the Japanese economy.2 Therefore, it is imperative to identify the risk factors and prevent functional decline in elderly adults at an early stage. In contrast to protein intake, energy intake decreases markedly with old age.3 Consequently, the ratio of protein energy to total energy increases with age. The importance of dietary energy intake for effective use of dietary protein intake has long been recognized.4 A previous study5 reported that inadequate energy intake lowers the efficiency
0002-8614/14/$15.00
2
IMAI ET AL.
2014
of protein use. Considering these findings, protein requirements may increase with age. Numerous factors related to functional decline have been identified. In general, older age, low educational level, sedentary lifestyle, obesity, poor cognitive function, and history of diseases such as hypertension and depression are associated with functional decline, but few studies have examined the risk factors related to loss of higherlevel functional capacity.6,7 Although a few prospective cohort studies have reported that several types of nutritional intake lead to functional decline, such as decline in cognitive ability8 and activities of daily living (ADLs),9 and increases in falls10 and frailty,11 early-stage functional decline in elderly persons associated with nutritional intake has not been reported. Nor has the relationship between protein intake and future functional capacity at an early stage in elderly persons been previously investigated. Identifying nutritional factors that contribute to maintaining higher-level functional capacity is important for prevention of future deterioration of ADLs. The aim of this study was to investigate the relationship between protein intake and future decline in higherlevel functional capacity in older community-dwelling adults in the Japanese general population based on 7 years of follow-up data.
METHODS
JAGS
The intake results were examined to determine associations with higher-level functional decline. The institutional review board of the Tohoku University School of Medicine and the Department of Health of the Ohasama town government approved this study.
Study Population Figure 1 shows a flow diagram of the present study. There were 2,614 individuals aged 60 and older in Ohasama in 1998, 2,348 of whom participated in the study from February 1 to March 28, 1998. Overall, 1,082 participants were excluded from the follow-up measurements for the following reasons: incomplete answers to the questionnaire at baseline (n = 372), not fully independent in basic ADLs (1.5 times), the same, or smaller (
Animal Protein Intake Is Associated with Higher-Level Functional Capacity in Elderly Adults: The Ohasama Study Eri Imai, PhD, RD,a Megumi Tsubota-Utsugi, PhD, MPH, RD,a Masahiro Kikuya, MD, PhD,b Michihiro Satoh, MSc,c Ryuske Inoue, MD, PhD,d Miki Hosaka, MSc,c Hirohito Metoki, MD, PhD,b Naomi Fukushima, MSc,e Ayumi Kurimoto, MSc,f Takuo Hirose, PhD,g Kei Asayama, MD, PhD,h Yutaka Imai, MD, PhD,c and Takayoshi Ohkubo, MD, PhDc,i
OBJECTIVES: To determine the association between protein intake and risk of higher-level functional decline in older community-dwelling adults. DESIGN: Prospective. SETTING: Ohasama Town, Japan. PARTICIPANTS: Residents (N = 1,007; mean age 67.4 5.5) free of functional decline at baseline; follow-up was conducted for 7 years. MEASUREMENTS: Nutrient and food intakes were determined using a validated 141-item food frequency questionnaire. Participants were divided into quartiles according to intake levels of total, animal, and plant protein. Subscales of the Tokyo Metropolitan Institute of Gerontology Index of Competence subscales were used to assess higher-level functional decline. Logistic regression analysis was used to examine the future risk of higher-level functional decline in relation to protein intake, with lowest protein intake as reference. RESULTS: During the study period, 24.4% of eligible participants reported declines in higher-level functional
From the aSection of the Dietary Reference Intakes, Department of Nutritional Epidemiology, National Institute of Health and Nutrition, Tokyo, Japan; bTohoku Medical Megabank Organization, Tohoku University, Sendai, Japan; cDepartment of Planning for Drug Development and Clinical Evaluation, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan; dDepartment of Medical Informatics, Graduate School of Medicine, Tohoku University, Sendai, Japan; eDivision of Community Health Nursing, School of Nursing, Fukushima Medical University, Fukushima, Japan; fDivision of Community Health Nursing, School of Health Sciences, Faculty of Medicine, Tohoku University, Sendai, Japan; gCenter for Interdisciplinary Research in Biology, College de France, Paris, France; hStudies Coordinating Centre, Division of Hypertension and Cardiovascular Rehabilitation, Department of Cardiovascular Diseases, University of Leuven, Leuven, Belgium; and i Department of Hygiene and Public Health, School of Medicine, Teikyo University, Tokyo, Japan. Address correspondence to Megumi Tsubota-Utsugi, Section of the Dietary Reference Intakes, Department of Nutritional Epidemiology, National Institute of Health and Nutrition, Toyama 1–23–1, Shinjyuku-ku, Tokyo 162–8636, Japan. E-mail: [email protected] DOI: 10.1111/jgs.12690
JAGS 2014 © 2014, Copyright the Authors Journal compilation © 2014, The American Geriatrics Society
capacity. After adjustment for putative confounding factors, men in the highest quartile of animal protein intake had significantly lower risk of higher-level functional decline than those in the lowest quartile (odds ratio (OR) = 0.41, 95% confidence interval (CI) = 0.20–0.83; P for trend .01). These associations were not seen in women (OR = 0.76, 95% CI = 0.41–1.34; P for trend .37). No consistent association was observed between plant protein intake and future higher-level functional decline in either sex. CONCLUSION: Higher protein, particularly animal protein, was associated with lower risk of decline in higherlevel functional capacity in older men. Animal protein intake may be a modifiable indicator for early detection and prevention of higher-level functional decline in elderly adults. J Am Geriatr Soc 2014.
Key words: animal protein; plant protein; functional capacity; healthy community dwelling; Japanese
W
ith the rapidly increasing life expectancy of the Japanese population, the percentage of individuals aged 65 and older has increased from 10.3% in 1985 to 20.1% in 2005.1 Collaterally, there has been a noticeable increase in the number of elderly people living with functional decline. Functional decline is now thought to have an enormous effect on hospitalization, institutionalization, and death and leads to adverse effects on the Japanese economy.2 Therefore, it is imperative to identify the risk factors and prevent functional decline in elderly adults at an early stage. In contrast to protein intake, energy intake decreases markedly with old age.3 Consequently, the ratio of protein energy to total energy increases with age. The importance of dietary energy intake for effective use of dietary protein intake has long been recognized.4 A previous study5 reported that inadequate energy intake lowers the efficiency
0002-8614/14/$15.00
2
IMAI ET AL.
2014
of protein use. Considering these findings, protein requirements may increase with age. Numerous factors related to functional decline have been identified. In general, older age, low educational level, sedentary lifestyle, obesity, poor cognitive function, and history of diseases such as hypertension and depression are associated with functional decline, but few studies have examined the risk factors related to loss of higherlevel functional capacity.6,7 Although a few prospective cohort studies have reported that several types of nutritional intake lead to functional decline, such as decline in cognitive ability8 and activities of daily living (ADLs),9 and increases in falls10 and frailty,11 early-stage functional decline in elderly persons associated with nutritional intake has not been reported. Nor has the relationship between protein intake and future functional capacity at an early stage in elderly persons been previously investigated. Identifying nutritional factors that contribute to maintaining higher-level functional capacity is important for prevention of future deterioration of ADLs. The aim of this study was to investigate the relationship between protein intake and future decline in higherlevel functional capacity in older community-dwelling adults in the Japanese general population based on 7 years of follow-up data.
METHODS
JAGS
The intake results were examined to determine associations with higher-level functional decline. The institutional review board of the Tohoku University School of Medicine and the Department of Health of the Ohasama town government approved this study.
Study Population Figure 1 shows a flow diagram of the present study. There were 2,614 individuals aged 60 and older in Ohasama in 1998, 2,348 of whom participated in the study from February 1 to March 28, 1998. Overall, 1,082 participants were excluded from the follow-up measurements for the following reasons: incomplete answers to the questionnaire at baseline (n = 372), not fully independent in basic ADLs (1.5 times), the same, or smaller (
