Substance use

Smoking

Dependency has a major impact on both individual health and society[1], and international guidelines recognise addiction as a disorder that affects both physical and psychosocial functioning[2]. Nicotine is used via cigarettes, e-cigarettes, cigars, snus, chewing tobacco and water pipes. All these forms lead to addiction, and the smoked forms in particular carry serious health risks[3]. Tobacco use raises blood pressure and damages blood vessels, weakens the immune system, increases the risk of organ damage and various cancers and impairs cognitive function. Genetic studies (Mendelian randomisation) confirm that this is cause and effect. The harm comes mainly from the combustion products; nicotine itself is the addictive engine[3], [4].

Stopping smoking is one of the most effective ways to improve physical and mental health. Those who stop before 45 avoid about 90% of the excess mortality from smoking, those who stop before 65 about two thirds, and the gain is measurable within a few years[5], [6].

Guidelines

For tobacco there is no safe level of use: the goal is to stop. A brief conversation with the doctor has a proven, if modest, positive effect on substance use[7].

How Synapse assesses this

Synapse reduces every form of nicotine to one comparable measure, shown as cigarettes per day, taking into account the average nicotine intake and the carcinogenic burden per product. That conversion is Synapse's own estimate (expert opinion): no validated equivalence between products exists. Any regular use, including weekly or occasional, keeps the score below optimal. For clinical interpretation the usual classification applies: light (fewer than 10), moderate (10 to 19) and heavy (20 or more cigarettes per day).

Synapse expresses the historical smoking burden in pack-years (packs per day times the number of years smoked)[8]. For ex-smokers Synapse takes into account the age at which they stopped, so that those who smoked longer and more heavily retain a higher burden than those who stopped in time; that rests on the published gain from stopping by age[5], [6]. For these rows Synapse shows no reference value: the goal is zero.

Alcohol

Excessive alcohol use is associated with an increased risk of cardiovascular, metabolic and neurodegenerative disease, cancer and premature death[9], [10]. Possible beneficial effects of moderate consumption do not outweigh the drawbacks[11]; a large meta-analysis found no protective effect of light drinking on mortality[10].

Guidelines

Recent guidelines stress that there is no safe level of consumption[12]. The Belgian Superior Health Council advises a maximum of 10 standard glasses per week[13], [14]; that is a ceiling, not a target. Binge drinking is drinking more than five (men) or four (women) glasses on one occasion. Brief interventions by the doctor have a proven, if modest, effect, most clearly for alcohol[7].

How Synapse assesses this

Synapse uses a question set based on the AUDIT-C[15]: drinking frequency, number of standard glasses per week (with stricter thresholds for women) and the frequency of binge drinking. The second question has been adapted from a daily to a weekly frequency to match the Belgian recommendation. Because of that adaptation, the published cut-offs and test characteristics of the original AUDIT-C do not apply unreservedly: Synapse uses the instrument as an internal risk score, not as a validated screening.

ItemReference
Alcohol≤ 2 glasses per week

Drugs

Alcohol and drug use are among the major causes of disease burden worldwide[1]. Recent figures point to an increase in the use and availability of illegal drugs, worldwide and in Europe[16], [17]. That has a major impact on physical and mental health; drug abuse is associated with higher mortality across the whole lifespan[18], [19].

Guidelines

For illegal drugs there is no safe level of use. A brief conversation with the doctor has a proven, if modest, effect on substance use[7].

How Synapse assesses this

Synapse assesses both soft and hard drug use and also includes excessive use of painkillers and sleep medication, to form a fuller picture of possible problems. Hard drugs weigh more heavily than soft drugs, and any use keeps the score below optimal. Members who indicate that they would rather not answer receive no score for this item. For these rows Synapse shows no reference value.

Screen time

Excessive screen time carries risks such as less physical activity and more sitting[20], a greater chance of metabolic dysregulation and overweight[21], and possibly more depressive symptoms[22]. The literature largely concerns adolescents and television-related sitting; for adults, the metabolic association and the effect of evening screen use on sleep in particular are well supported[23], [24].

Guidelines

For adults there is no external guideline with a maximum number of hours of screen time.

How Synapse assesses this

Synapse assesses not only total duration (social media, TV and games combined) but also use just before bedtime. Synapse takes both into account. The classification in hours is Synapse's own, not an external guideline. For these rows Synapse shows no reference value.

Coffee

Caffeine blocks the adenosine receptors A1 and A2A and so inhibits the build-up of sleep pressure; the half-life averages 2.5 to 4.5 hours, but varies strongly with CYP1A2 genotype, smoking, oral contraception and pregnancy. The polyphenols in coffee, including decaffeinated coffee, improve insulin sensitivity and protect the liver[25].

Large overview studies show that moderate coffee drinkers (about 2 to 4 cups per day) may benefit from a lower risk of various conditions and a lower risk of death[26], [27]. The umbrella review by Poole shows a U-shaped relationship with the greatest benefit around 3 to 4 cups per day[26]. Excessive or late intake can lead to insomnia, palpitations, migraine and habituation[28], [29]. The association with lung cancer reported in some meta-analyses[28] probably rests largely on confounding by smoking and is not found in never-smokers.

Guidelines

EFSA considers up to 400 mg of caffeine per day safe for healthy adults, and 200 mg per day during pregnancy[25].

How Synapse assesses this

Synapse assesses both the daily amount and coffee after 3 pm, given its negative influence on sleep quality[29]. Synapse takes both into account. Decaffeinated coffee does not count towards the amount.

ItemReference
Coffee≤ 4 cups per day

Caffeine and sleep

Caffeine shortens total sleep time by about 45 minutes and deep sleep by about 11 minutes; a coffee has to be drunk about 9 hours before bedtime to avoid that sleep loss[29]. Unfiltered coffee raises LDL cholesterol via cafestol[25].

Soft drinks

Sugar-sweetened drinks (soft drinks, sports and energy drinks, sweetened milk and fruit drinks) deliver energy without appreciable micronutrients. Liquid sugar satiates poorly: the energy is barely compensated for at subsequent meals. The fructose is metabolised in the liver on first pass, drives de novo lipogenesis and raises uric acid, with atherogenic dyslipidaemia, visceral fat accumulation and fatty liver as a result, even independently of weight[30].

Meta-analyses show a consistent dose-response relationship with cardiovascular disease, type 2 diabetes and obesity[30], [31], [32]. Per daily serving, the risk of coronary heart disease rises by about 17%[33], and per 250 ml per day the risk of type 2 diabetes by about 19% and of obesity by about 12%[31]. At two or more servings per day, cardiovascular mortality is about 31% higher[34].

Guidelines

Guidelines advise keeping intake as low as possible, with water as the standard drink. An umbrella review on sugar consumption advises fewer than one sugar-sweetened drink per week[35]. When reading labels, less than 5 g of sugar per 100 ml serves as a reference point. In Belgium, average consumption is around 130 g per day across the whole population and around 200 g per day among adolescents[36].

How Synapse assesses this

Synapse asks how often soft drinks, fruit juice, sports and energy drinks and diet variants are drunk, and takes the type of drink into account. Fruit juice shares the free fructose and glycaemic load of soft drinks and therefore counts. The classification is Synapse's own.

Diet, zero and energy drinks

Sweetener-based drinks contain no sugar and in that respect are better than the sugared variant, but at high intake they too are associated with higher mortality[34]. They are a step in cutting down, not an end point. Energy drinks contain as much sugar as soft drinks, plus per can as much caffeine as one to two cups of coffee.

Developed and reviewed with the Synapse medical advisory board.

References

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  12. [12]Department of Health. UK Chief Medical Officers' low risk drinking guidelines (2016).
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  17. [17]United Nations Office on Drugs and Crime. World Drug Report 2024 (2024).
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Put it into practice

Addiction