CARDIOLOGY
“Our study indicates that microbiota might have an important role in maintaining health and could help us develop novel treatments,” said study author Dr. Hilde Groot of University Medical Centre Groningen, the Netherlands.
The human gut microbiome is the totality of microorganisms (generally bacteria and single-celled organisms called archaea) and their collective genetic material present in the digestive tract. Small-scale studies have suggested a link between the gut microbiome and individual diseases. This study, for the first time, investigated multiple diseases and other traits in one cohort – revealing the staggering extent to which the microbiome influences sickness and health. The analysis used genetic data as a proxy for microbiome composition. Dr. Groot explained: “Previous research has shown that the human gut microbiome composition could be partially explained by genetic variants. So, instead of directly measuring the make-up of the microbiome, we used genetic alterations to estimate its composition.”
The study included 422,417 unrelated individuals in the UK Biobank who had undergone genotyping to identify their genetic make-up. Information was also collected on a wide range of diseases and other characteristics including BMI and blood pressure. The average age of participants was 57 years and 54% were women. The researchers found that higher levels of eleven bacteria (estimated from genetic data) were associated with a total of 28 health and disease outcomes. These included chronic obstructive pulmonary disease (COPD), atopy (a genetic tendency to develop allergic diseases like asthma and eczema), frequency of alcohol intake, high blood pressure, high blood lipids, and BMI. To take one example, higher levels of the genus Ruminococcus were linked with increased risk of high blood pressure. Regarding alcohol consumption, Dr. Groot said: “What we eat and drink is connected to microbiome content, so we studied the links with meat, caffeine, and alcohol. We observed a relationship between raised levels of Methanobacterium and drinking alcohol more often. It is important to stress that this is an association, not a causal relation, and more research is needed.” A real strength of the study was conducting a broad analysis in the same group of people. Dr. Groot said: “Considering that the results were observed in one cohort, this cautiously supports the notion that microbiota and the substances they produce (called metabolites) provide links between numerous diseases and conditions. The findings may help identify common pathways. Nevertheless, more research (for example in other cohorts) is needed to
Gut microbiota have an important role in maintaining health
validate our findings.” She concluded: “Follow-up studies are required to study causality before giving concrete advice to the public and health professionals. This study provides clues where to go.”
Teenage depression
The event also highlighted other risk factors, linked with heart health and outcomes – for example, depression or anxiety in adolescence is linked with a 20% greater likelihood of having a heart attack mid-life.4 In a warning to parents, study author
Dr. Cecilia Bergh of Örebro University in Sweden, said: “Be vigilant and look for signs of stress, depression or anxiety that is beyond the normal teenage angst: seek help if there seems to be a persistent problem (telephone helplines may be particularly helpful during the COVID-19 pandemic). If a healthy lifestyle is encouraged as early as possible in childhood and adolescence it is more likely to persist into adulthood and improve long-term health.”
There are indications that mental well- being is declining in young people. This study investigated whether conditions like depression in adolescence (age 18 or 19) are associated with a higher risk of cardiovascular disease in adulthood. The researchers also examined the possible role of stress resilience (ability to cope with stress in everyday life) in helping to explain any associations. The study included 238,013 men born between 1952 and 1956 who underwent extensive examinations in late adolescence (as part of their assessment for compulsory military service) and were then followed into middle age (up to the age of 58
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years). The assessments at the age of 18 or 19 years included medical, psychiatric, and physical examinations by physicians and psychologists. Stress resilience was measured by an interview with a psychologist and a questionnaire, and based on familial, medical, social, behavioural and personality characteristics.
A total of 34,503 men were diagnosed with a non-psychotic mental disorder (such as depression or anxiety) at conscription. Follow-up for cardiovascular disease was through hospital medical records. The study found that a mental disorder in adolescence was associated with the risk of having a myocardial infarction (heart attack) by middle age. Compared to men without a mental illness in adolescence, the risk of myocardial infarction was 20% higher among men with a diagnosis – even after taking into account other characteristics in adolescence such as blood pressure, body mass index, general health, and parental socioeconomic status.
The association between mental illness
and heart attack was partly – but not completely – explained by poorer stress resilience and lower physical fitness in teenagers with a mental illness. “We already knew that men who were physically fit in adolescence seem less likely to maintain fitness in later years if they have low stress resilience,” said Dr. Bergh. “Our previous research has also shown that low stress resilience is also coupled with a greater tendency towards addictive behaviour, signalled by higher risks of smoking, alcohol consumption and other drug use.” Dr. Bergh said: “Better fitness in
NOVEMBER 2020
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