Which is worse: smoking a few cigarettes every day for years or smoking heavily for a shorter amount of time?

There were many studies reporting the effects of tobacco use in general. This includes smoking cigarettes, cigars, pipes, and other substances. It also includes smokeless tobacco products.

In a few studies it appears there are an equal number of problems that can occur with either choice. Studies show smoking more than 15 years increases the risk of sciatica (shooting pain down the leg). Smoking volume (number of cigarettes) isn't a factor here.

Number of cigarettes and the number of years smoked are both linked to chronic low back pain. Smoking increases the risk of osteoporosis and damage to the bones. It's not clear if volume or duration or both are key factors.

New research into the effects of smoking after surgery shows many problems. Smokers heal slower and return to work later. Again smoking in general isn't broken down into volume or duration. Since tobacco use is a known health hazard, most of the research and education is towards stopping, not just reducing it.