Age is related to the incidence of periodontal destruction: "...in a well-maintained population who practises oral home care and has regular check-ups, the incidence of incipient periodontal destruction increases with age, the highest rate occurs between 50 and 60 years, and gingival recession is the predominant lesion before 40 years, while periodontal pocketing is the principal mode of destruction between 50 and 60 years of age. "There are a variety of periodontal risk factors which can affect the prevalence, rate, extent and severity of the disease progression. Major risk factors include smoking, lack of oral hygiene with inadequate plaque biofilm control. There is a slow to moderate rate of disease progression but the patient may have periods of rapid progression ("bursts of destruction"). Chronic periodontitis can be associated with local predisposing factors (e.g. tooth-related or iatrogenic factors). The disease may be modified by and be associated with systemic diseases (e.g. diabetes mellitus, HIV infection) It can also be modified by factors other than systemic disease such as smoking and emotional stress, anxiety and depression. Care should be taken however, when diagnosing a patient who smokes as smoking can alter some of the results of an examination. In smokers, the gingiva are pale and fibrous and tend to bleed less while being probed due to the effect of nicotine on the vasculature by vasoconstricting them. Thus, a lowered response is produced and this explains why incorrect data can be gained. There is also an increase in supragingival calculus alongside visible nicotine staining.
The 2017 classification of Periodontal Diseases and Conditions includes:Periodontitis:

Necrotizing periodontal diseases
Periodontitis
Periodontitis as a manifestation of systemic diseaseTherefore, in accordance to the 2017 classification, a diagnosis would be achieved through the patient assessment individually on the basis of:

Type
Distribution: localised (up to 30% of teeth) or generalised (more than 30% of teeth) and the molar/incisor pattern
Stage and grading
Stages: I (early/mild) with <15% or <2mm interproximal bone loss, II (moderate) with coronal third of root bone loss, III (severe) with mid third of root bone loss, IV (very severe) with apical third of root bone loss
Grading: A (slow) with <0.5% bone loss/age, B (moderate) with 0.5-1.0% bone loss/age, C (rapid) with >1.0% bone loss/age
Status: stable, remission or unstable (see Table 1)
Risk factors, which include systemic diseases such as diabetes or extrinsic factors such as smoking. Treatment
There is professional agreement among dentists that smoking cessation and good oral hygiene are key to effective treatment and positive outcomes for patients. Similarly, any plaque retentive factors which exist and are modifiable should be corrected, such as overhangs on restorations. Treatment can involve both non-surgical and surgical therapies. The typical initial treatment known to be effective is scaling and root planing (SRP) to mechanically debride the depths of the periodontal pocket and disrupt the biofilm present. This is done using a powered ultrasonic or sonic scaler and/or unpowered hand instruments. "In patients with chronic periodontitis, subgingival debridement (in conjunction with supragingival plaque control) is an effective treatment in reducing probing pocket depth and improving the clinical attachment level.