A nice study was recently published by Anner et al in Implant dentistry (Volume 19 - Issue 1 - pp 57-64). The authors performed  a large cohort study to evaluate the factors associated with long-term implant survival in a large number of patients.
 

The sample consisted of 475 patients who had dental implants and referred to a private clinic for a period of 10 years. Patients were followed regarding smoking habits, periodontal conditions and diabetes mellitus.

During this long period of follow up, the failures rate of the implants was only 4.7%. However, More than one-half of the patients required a structured supportive periodontal program.

Smoking and attendance in a regular supportive periodontal program were statistically associated with implant survival. Diabetes mellitus was not related to implant survival in this patient cohort.

Reference:

Anner et al. Implant dentistry (Volume 19 - Issue 1 - pp 57-64).