Bones, muscles and why smokers heal badly

Smoking reduces bone mineral density through several routes: it interferes with calcium absorption, lowers oestrogen levels, is toxic to the osteoblasts that build new bone, and often comes with lower body weight, itself a risk factor.

The end result is a higher risk of osteoporosis and fractures, especially hip fractures, where smoking is an established risk factor. A hip fracture in an older adult is not a broken bone, it is frequently the beginning of permanent loss of independence.

Bone healing depends on new blood vessel growth into the fracture site. Nicotine constricts vessels and carbon monoxide reduces oxygen delivery, so the biological repair crew arrives short-staffed.

Studies show smokers take significantly longer to heal fractures and have higher rates of non-union, where the bone never fully joins and requires further surgery.

Spinal fusion is the clearest example: failure rates in smokers can be roughly double those of non-smokers, which is why many spine surgeons require documented cessation before operating.

Intervertebral discs have almost no blood supply and depend on diffusion for nutrients. Smoking reduces that already marginal supply, and is associated with accelerated disc degeneration and higher rates of chronic low back pain.

Tendon and rotator cuff problems are also more common and heal worse in smokers.

Carbon monoxide binds to haemoglobin with far greater affinity than oxygen, so a smoker's blood carries less usable oxygen. Combine that with narrowed airways and reduced lung function and aerobic capacity drops measurably.

Smokers also show reduced muscle strength and greater fatigue in exercise testing. Many people notice improvement in stamina within 2 to 12 weeks of quitting, one of the earliest visible rewards.