Our smoking status and body mass index (BMI) are together linked to 226 medical conditions, from heart failure and hernias to sleep apnoea and nail disorders.
at the University of Oxford used data on 500,000 participants of the UK Biobank study to estimate the extent to which smoking or our BMI influences our risk of various conditions. your weight is healthy.
In 11 of the 226 conditions, smoking or our BMI may be responsible for more than half of the condition鈥檚 onset, with genetics or other lifestyle habits contributing to the rest.
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For example, atherosclerosis, when the arteries become clogged by fatty substances called plaques, is 73 per cent down to smoking or our BMI, with other factors making up the remaining 27 per cent, the study suggests.
鈥淭he proportions of diseases in the study that are attributed to smoking and/or BMI is quite staggering,鈥� says Webster.
鈥淢ost of the strong associations with specific diseases have been observed by prior publications, but many of these associations have only become recognised recently.鈥�
For example, our BMI influences our risk of nerve damage, infections and degeneration of the spine, while smoking may cause fungal infections or affect the ulnar nerve, which transmits electrical signals to muscles in the forearm and hand, says Webster.
at Imperial College London hopes the findings may serve as a reminder of the serious health implications associated with smoking and our BMI, particularly being overweight.
鈥淚 think this helps highlight to policy-makers how urgently we need to work to address these problems,鈥� he says.
Others have called for a note of caution regarding some of the more obscure associations with conditions. For example, while the study suggests that smoking and our BMI might influence our susceptibility to flu and tension headaches, a combination of factors may be responsible.
Although Webster accounted for the participants鈥� socioeconomic background and educational status, other crucial confounding factors may be at play, such as an individual鈥檚 stress levels, says at the University of Bath, UK.
鈥淲e have to look at whether there鈥檚 a plausible biological pathway between smoking, BMI and each of these diseases,鈥� she says. 鈥淛ust because you find an association doesn鈥檛 mean they鈥檙e directly causally related.鈥�
Perhaps surprisingly, the study also suggests that smoking may protect against some conditions, such as Parkinson鈥檚 disease.
鈥淭his unusual connection was mentioned in the Royal College of Physicians鈥� 2018 report, , which estimated the cost to hospital care services of all of those different smoking-related diseases,鈥� says at the University of Sheffield, UK.
, including speculation on the neuroprotective effects of nicotine, scientists are yet to find a satisfactory explanation.
鈥淚鈥檓 always quite suspicious of protective effects, especially when it comes to smoking because you often get a survivor bias,鈥� says Taylor. 鈥淵ou often see in epidemiology that smoking appears to protect against dementia, while all that鈥檚 happened is that everyone who didn鈥檛 get dementia died earlier from lung cancer.鈥�
Overall, the research highlights how much the burden on healthcare services could be reduced by encouraging people to quit smoking and maintain a healthy weight, according to Taylor.
鈥淚t makes us realise that actually we鈥檝e got two huge causes of disease morbidity which are both very preventable,鈥� she says.
medRxiv
