Association of Coffee, Green Tea, and Caffeine With the Risk of Dementia in Older Japanese People

Nana Matsushita; Yuta Nakanishi; Yumi Watanabe MD; Kaori Kitamura PhD; Keiko Kabasawa MD; Akemi Takahashi PhD; Toshiko Saito PhD; Ryosaku Kobayashi PhD; Ribeka Takachi PhD; Rieko Oshiki PhD; Shoichiro Tsugane MD; Masayuki Iki MD; Ayako Sasaki MD; Osamu Yamazaki MD; Kei Watanabe MD; Kazutoshi Nakamura MD

Disclosures

J Am Geriatr Soc. 2021;69(12):3529-3544. 

In This Article

Abstract and Introduction

Abstract

Objectives: Coffee, green tea, and caffeine are potential preventive factors for dementia, but the underlying evidence is insufficient. This study aimed to examine associations between the consumption of coffee, green tea, and caffeine and dementia risk in middle-aged and older people.

Methods: This was a cohort study with an 8.0-year follow-up. Participants were community-dwelling individuals (n = 13,757) aged 40–74 years. A self-administered questionnaire survey was conducted in 2011–2013. Predictors were the consumption of coffee/green tea, from which caffeine consumption was estimated. The outcome was incident dementia obtained from the long-term care insurance database. Covariates were demographic factors, body mass index, physical activity, energy, smoking, drinking, and disease history. Adjusted hazard ratios (HRs) were calculated using Cox proportional hazards models. HRs were also calculated using a Cox model with delayed entry.

Results: The number of dementia cases during the study period was 309. Participants with higher coffee consumption had lower HRs (adjusted p for trend = 0.0014), with the fifth quintile (≥326 ml/day) having a significantly lower HR (0.49, 95% confidence interval [CI]: 0.30–0.79) than the first quintile (<26 ml/day, reference). Similarly, participants with higher caffeine consumption had a significantly lower HR (adjusted p for trend = 0.0004) than the reference. The Cox model with delayed entry yielded similar results. These associations were significant in men, but not in women. Moreover, participants who consumed 2–2.9 cups/day and ≥3 cups/day of coffee had lower HRs (0.69, 95% CI: 0.48–0.98 and 0.53, 95% CI: 0.31–0.89, respectively) than those who consumed 0 cup/day. The association between green tea consumption and reduced dementia risk was significant (adjusted p for trend = 0.0146) only in the 60–69 years age subgroup.

Conclusions: High levels of coffee and caffeine consumption were significantly associated with a reduced dementia risk in a dose-dependent manner, especially in men. Moreover, coffee consumption of ≥3 cups/day was associated with a 50% reduction in dementia risk.

Introduction

Dementia is a syndrome resulting from diseases that impact the brain, is usually of a chronic or progressive nature, and is accompanied by a disturbance of multiple higher cortical functions.[1] The number of people with dementia was globally estimated to be 47 million (roughly 5% of the world's older population) in 2015, and is projected to reach 75 million in 2030.[2] In Japan, where aging of the population is accelerating, 4.6 million people aged 65 and older (roughly 14%) had dementia in 2012, and 7 million people are expected to develop dementia by 2025.[3] Costs of caring for people with dementia worldwide is estimated to reach 2 trillion dollars (USD) by 2030.[2] For at least these reasons, the prevention of dementia is of high priority.

Many studies have examined factors that are associated with dementia, the most common type of which is Alzheimer's disease (AD). These efforts have identified modifiable preventive factors, including education, physical activity, and smoking cessation.[4] Recently, the consumption of coffee and green tea has been reported to be a potential preventive factor.[5,6]

Coffee contains caffeine and many biologically active phytochemicals (e.g., polyphenols), and shows promise in preventing incommunicable chronic diseases, such as cancer, vascular diseases, and diabetes mellitus, type II.[7] In line with this, coffee or caffeine is suggested to be a potential therapeutic against AD, possibly by reducing amyloid-β (Aβ) in the brain.[8] Green tea also contains caffeine and various polyphenols, including epigallocatechin gallate (EGCG), which has antioxidant and anti-inflammatory effects.[9] Green tea has also been suggested to reduce the risk of AD, through its anti-Aβ effects.[10] Despite reports on the benefits of coffee, green tea, and caffeine, evidence from epidemiologic studies remains insufficient. A systematic review by Larsson et al. suggested that, while some cohort studies showed a positive association between coffee consumption and dementia risk, the meta-analysis of eight studies overall did not reveal such an association.[5] The authors indicated the need for further well-designed epidemiologic studies,[5] in particular, cohort studies. With regard to the association between green tea and dementia, only a few cohort studies have been conducted on the topic.[6]

In 2011, we established a large-scale, population-based cohort to study age-related diseases, including bone diseases and dementia (Murakami cohort study).[11] A specific feature of the Murakami cohort is that it includes middle-aged and older individuals, while other cohort studies targeted older populations than ours.[5,6] Thus, our study may be able to identify modifiable factors of dementia in earlier stages than other cohort studies. Against this backdrop, the present study aimed to examine associations between the consumption of coffee, green tea, and caffeine and dementia risk in middle-aged and older people in an 8-year follow-up of the Murakami cohort.

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