What is Down Syndrome?
Down Syndrome, also known as trisomy 21, is a genetic disorder caused by having either a full or partial extra copy of chromosome 21. This additional genetic material disrupts the normal development pathway and results in the physical traits of Down Syndrome [1, 2, 3, 4, 5, 6, 7].
People with Down syndrome generally have some degree of physical and mental developmental delays and disabilities. The syndrome is the most common genetic cause of moderate to severe samples of mental retardation and affects current births in about 1 in 700 live births. The condition produces a distinctive pattern of mental retardation, plus a variable group of characteristics [8, 1, 2, 3, 4, 5, 6, 7].
What are the Causes of Down Syndrome?
Down Syndrome is caused (in virtually all patients) by trisomy 21, an extra copy of chromosome 21 in all of the patient's body cells. In much rarer cases, it can be caused by a trisomy 21 chimera or trisomy 21 in just some cells in the body. This extra copy of chromosome 21 is believed to produce a different developmental pattern of the body and brain and thereby account for the physical and mental features of the condition [8, 1, 2, 3, 4, 5, 6, 7].
Down Syndrome is, in the overwhelming majority of cases, congenital (present from birth) and non-hereditary (parents do not pass it on). It is caused randomly when cells divide in the developing foetus. What causes Down Syndrome or how many different factors might be involved is unknown. One known risk factor is maternal age: women aged 35 and over are more likely to have children with Down Syndrome [9, 1, 4].
Risk Factors of Down Syndrome
Down Syndrome, which is technically referred to as Trisomy 21, is a genetic disorder where there is an extra copy of chromosome 21. Various factors have been identified that lead to an increased chance of their child having Down Syndrome.
Advanced maternal age is the first huge risk factor. Each year a woman gets older—past age 35 or so—the chance that some of her eggs will have an abnormal number of chromosomes increases exponentially due to ageing eggs being more prone to errors in meiotic cell division [10].
Parental consanguinity, the marriage of close relatives, has also been linked to an increased risk for Down Syndrome, including both direct parental consanguinity and grand-maternal consanguinity [11, 12].
Other maternal health conditions and behaviours have also been linked to higher risk, especially diabetes mellitus, maternal fever, and the use of either antibiotics or oral contraceptive pills during pregnancy [11, 12].
Environmental factors such as smokeless chewing tobacco and oral-contraceptive pills have also been associated with an increased risk of Down Syndrome. They could also interact with or amplify age-related risk [13].
Genetic factors come into play. Specific mutations in the methylenetetrahydrofolate reductase (MTHFR) and reduced-folate-carrier1 (RFC1) genes, for example, have been found to increase the risk of Down Syndrome [14, 15].
Furthermore, people with Down syndrome are more susceptible to illnesses such as:
- Alzheimer’s disease
- Leukaemia
- Nighttime awakenings [16, 17, 9].
Alcohol and its Influence on Genetic Disorders
Even alcohol itself has a way of causing genetic conditions – in some cases, disorders of alcohol metabolism. This disorder includes deficiencies in the enzyme aldehyde dehydrogenase 2 (ALDH2), which is needed for liver ethanol metabolism [18]. About 8% of the human population and between 35-45% of East Asians are carriers of this genetic disease [18].
People suffering from a deficiency of the ALDH2 enzyme end up with elevated levels of acetaldehyde when they drink, leading to facial flushing, pounding heart (tachycardia), nausea and headache – that is, ‘Alcohol Flushing Syndrome’ [18].
A more severe outcome of ALDH2 deficiency is the elevated risk for aerodigestive tract cancers for those who develop chronic alcohol consumption. Specifically, moderate-to-heavy ethanol consumption by ALDH2 homozygotes is linked to a 7-12-fold increased risk for oesophagal cancer [18].
Another alcohol-related genetic disorder is Fanconi anaemia (FA), an inherited bone marrow failure syndrome due to defects of any one of 22 genes so far identified to be associated with the heterogeneous recessive disease (the hereditary breast and ovarian cancer (HBOC) genes BRCA1 and BRCA2 are also FANC [19]).
Nevertheless, alcohol can potentiate genetic disorders, and not all ethanol genotypes affect diseases equally. For example, the ALDH2 rs671 genotype does not modulate breast cancer incidence among Japanese BRCA1/2-mutation carriers [19].
To sum up, alcohol can indeed influence genetic disorders, but this only happens in some disorders which are related to how alcohol can be metabolised. The effects can differ from gene to gene and from person to person.
Can People With Down Syndrome Drink Alcohol?
The keys to answering this question lie in the complexities of the issue. Yes, people with Down Syndrome can drink alcohol. After all, they can engage in most behaviours, including consuming what others are consuming. But differently abled individuals can be affected by this substance in different ways from those without.
The evidence suggests that adults with intellectual disability, including those with Down syndrome, tend to consume alcohol at much lower rates than the general population [20, 21]. Several possible explanations exist, including exclusion by society and culture and choice [21].
But when people with Down Syndrome do drink, the consequences to their health can be substantial: there is an increased incidence of children with both Fetal Alcohol Syndrome and Down Syndrome being born, particularly to second-generation alcoholic mothers [22]; people with intellectual disabilities make up 9% of all children with potentially harmful levels of drinking [23].
Moreover, alcohol misuse predicts behavioural and social problems and raises ethical quandaries regarding treatment and testing [20]. It is worth noting that those with Down Syndrome who had never resided in an institution have been found to have a lower frequency of positive hepatitis B antigen; this may be exacerbated with alcohol [24].
Overall, although individuals with Down Syndrome can drink alcohol, there are many considerations relating to both potential health risks and social problems that make the issue complex. Those with Down Syndrome and their caretakers must be informed about the dangers of alcohol and be responsible for adult choices in terms of alcohol consumption.