Association between bowel habits and dementia.便習慣と認知症との関連

Association between bowel habits and dementia.

便習慣と認知症との関連https://epi.ncc.go.jp/jphc/outcome/9173.html

-Report on results from the Multi-Purpose Cohort Study (JPHC Study)-.

　We are conducting research to clarify the relationship between various lifestyle habits and diseases such as cancer, stroke and myocardial infarction, and to help prevent lifestyle-related diseases and extend healthy life expectancy in the Japanese population. In 2000 (Heisei 12) and 2003 (Heisei 15), approximately 19,000 men and 23,000 women aged 50-79 years who responded to a questionnaire from among those living in the five health centres (as of 2019) in Yokote, Akita Prefecture; Saku, Nagano Prefecture; Chubu, Okinawa Prefecture; Mito, Ibaraki Prefecture; and Chuoto, Kochi Prefecture, were Based on the results of a survey that followed up until 2016, we have published an article in a professional journal on the relationship between defecation habits and dementia ("dementia") as ascertained from information on long-term care insurance certification (Public Health, June 2023, web ahead of print).

Gut function has been reported to be associated with cognitive dysfunction and dementia (particularly Alzheimer's disease) via a brain-gut correlation (interconnection between brain function and gut function) involving the gut microbiota. It has been speculated that changes in the gut microbiota can induce oxidative stress (cellular damage caused by oxidative reactions) and systemic inflammation, which may be involved in the pathogenesis of neurodegenerative diseases, including dementia. Defecation habits (frequency and hardness of stools), a simple indicator of bowel function, may be related to dementia via the function of intestinal bacteria, but no previous studies have investigated the relationship between defecation habits and dementia in the general population. We therefore investigated the association between defecation habits (stool frequency and firmness) and subsequent risk of dementia in a multi-purpose cohort study.

Defecation habits were ascertained through questionnaires at the beginning of the survey (2000-2003). The frequency of bowel movements was determined by the question "How often do you have bowel movements?" (less than three times a week, three to four times a week, five to six times a week, once daily and more than twice daily). The hardness of stools was ascertained from the answers to the question "What is your usual stool condition?" (diarrhoea, soft stool, normal stool, hard stool, particularly hard stool, repeated diarrhoea and constipation). In the analysis of stool frequency, the risk of developing dementia (hazard ratio) in the group that gave the other answers was calculated on the basis of 'once daily' and 'normal stool' in the analysis of stool hardness, respectively. The analysis statistically took into account age, body mass index (BMI), smoking, alcohol consumption, medical history (diabetes, hypertension, stroke), physical activity, presence of family members living in the same household, presence of doctor-prescribed oral medication and dietary fibre intake, removing these effects as much as possible. In addition, bowel symptoms were analysed separately for men and women, as they were more frequently reported by women.
―多目的コホート研究（JPHC研究）からの成果報告―

　私たちは、いろいろな生活習慣と、がん・脳卒中・心筋梗塞などの病気との関係を明らかにし、日本人の生活習慣病予防と健康寿命の延伸に役立てるための研究を行っています。平成12年（2000年）と平成15年（2003年）に、秋田県横手、長野県佐久、沖縄県中部、茨城県水戸、高知県中央東の5保健所（呼称は2019年現在）管内にお住まいだった方々のうち、アンケートに回答した50～79歳の男性約19,000名、女性約23,000名を平成28年（2016年）まで追跡した調査結果にもとづいて、排便習慣と、介護保険認定情報から把握した認知症（以下、認知症）との関連を調べた結果を専門誌で論文発表しましたので、ご紹介します（Public Health, 2023年6月Web先行公開）。

　腸の機能は、腸内細菌叢が関与する脳腸相関（脳の機能と腸の機能には相互に関連があること）を介して認知機能障害や認知症（特にアルツハイマー病）と関連することが報告されています。腸内細菌叢の変化は、酸化ストレス（酸化反応による細胞の障害）や全身性の炎症をひきおこし、認知症を含む神経変性疾患の病態にかかわることが推測されています。また、腸の機能の簡便な指標である排便習慣（便の頻度と硬さ）は、腸内細菌の働きを介して、認知症と関連することが考えられますが、一般住民において、排便習慣と認知症の関連を調べた先行研究はありません。そこで、私たちは、多目的コホート研究において、排便習慣（便の頻度と硬さ）とその後の認知症リスクとの関連について調べました。

　排便習慣は、調査開始時（2000年から2003年）のアンケートで把握しました。便の頻度は、「便通はどのくらいの頻度でありますか？」という質問に対する回答の（週に3回未満、週に3～4回、週に5～6回、毎日1回、毎日2回以上）から把握しました。便の硬さは、「普段の大便の状態は？」という質問に対する回答の、（下痢便、軟便、普通の便、硬い便、特に硬い便、下痢と便秘を繰り返す）から把握しました。便の頻度の解析では、「毎日1回」、便の硬さの解析では、「普通の便」を基準として、他の回答をしたグループにおける認知症になるリスク（ハザード比）をそれぞれ算出しました。解析では、年齢、体格（BMI）、喫煙、飲酒、既往歴（糖尿病、高血圧、脳卒中）、身体活動、同居家族の有無、医師が処方した内服薬の有無、食物繊維の摂取量を統計学的に考慮し、これらの影響をできるだけ取り除きました。また、腸の症状は女性の訴えが多いことなどから、男女別に解析しました。

男女ともに、便の頻度が少ないグループほど、認知症リスクが高い

　2007年から2016年までの要介護認定情報から、男性で1,889名（9.7％）、女性で2,685名（11.7％）が認知症と診断されていることを確認しました。排便頻度が毎日1回のグループに対して、週3回未満の男性では約1.8倍、女性では約1.3倍認知症のリスクが高く、排便頻度が少ないグループほど認知症リスクが高くなりました(図1)。性別にみると、この傾向は男性でより強くみられました。
For both men and women, the less frequent the stool group, the higher the risk of dementia.

　Based on information from 2007 to 2016 on care needs, 1,889 men (9.7%) and 2,685 women (11.7%) were diagnosed with dementia. The risk of dementia was approximately 1.8 times higher in men and 1.3 times higher in women who defecated less than three times a week, compared to the group who defecated once daily, and the risk of dementia was higher in the group who defecated less frequently (Figure 1). In terms of gender, this trend was stronger in men.

What the study revealed.

　For both men and women, the risk of dementia was higher the lower the frequency of defecation and the harder the stool. Less frequent defecation and firmer stools are associated with delayed transit time of stool through the intestinal tract. Delayed bowel transit time has been reported to cause a decrease in short-chain fatty acids, which are metabolites of intestinal bacteria, and a decrease in short-chain fatty acids may cause oxidative stress and increase the risk of dementia. Decreased short-chain fatty acids may also increase the risk of dementia via systemic inflammation due to increased permeability of the intestinal tract and immune activation. With regard to gender differences, differences in the composition of the gut microbiota due to gender may have an impact.

　Limitations of the study include the fact that the dementia defined in this study could not be classified according to dementia types such as Alzheimer's disease or vascular dementia, the specific types of oral medication, including laxatives, could not be ascertained, and changes in defecation habits after the time of the questionnaire could not be ascertained. Further research, including on the mechanism, is needed.

A word from the 12th generation Kita Juzaemon❣
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12代喜多重左衛門からの一言
何事も「日常茶飯事」という古からの文言は大切です。日常茶飯事に食事は忘れることはないでしょう。また、茶を飲む習慣も同じことです。OMGT LLCの抹茶ペーストは、800年以上も続く日本文化に革命を起こしました。より身近に素晴らしい抹茶をペーストして飲むことができる優れものです。カテキンや、不溶性食物繊維、水溶性食物繊維が豊富で「朝のすっきり」には役に立てます。日ごろの良い習慣を確立しましょう。