To investigate the efficacy, safety, and tolerability of linagliptin 5 milligrams once a day compared to placebo as as add-on therapy for 24 weeks to stable basal insulin treatment in elderly patients, 60 years of age and older, with Type 2 Diabetes Mellitus and insufficient glycaemic control.Stable background therapy of metformin and/or alpha-glucosidase inhibitors is also allowed.

In addition, this trial will assess if linagliptin reduces the risk of hypoglycaemia when added to background basal insulin therapy. The treatment duration of this trial (24 weeks) will enable assessment of the clinically relevant endpoint of a decrease in glycosylated Haemoglobin, a well-accepted measurement of chronic glycaemic control.

Inclusion criteria:

• Patients must sign and date an Informed Consent consistent with International Conference on Harmonisation and Good Clinical Practice guidelines and local regulations prior to any evaluation and participation in the trial.
• Male and female patients with a clinical diagnosis of Type 2 Diabetes Mellitus, at the time of Informed Consent, who are:
• 60 years of age or older at informed consent or Screen Visit,
• taking stable doses of basal or biosimilar basal insulin [strictly inclusive of: insulin neutral protamine Hagedorn and isophane insulin; Humalog Basal (a suspension of insulin lispro protamine); insulin degludec; insulin detemir; and insulin glargine] for at least 4 weeks prior to randomisation (Visit 3) with dose adjustments up to a maximum of plus or minus 20% of baseline being allowed,
• may or may not be taking metformin immediate release or extended release [if the patient is taking metformin, stable dose must be maintained for at least twelve weeks without dose adjustments prior to randomisation (Visit 3)], and
• may or may not be taking alpha-glucosidase inhibitors [acarbose, miglitol, and voglibose; if the patient is taking alpha-glucosidase inhibitors, stable dose must be maintained for at least twelve weeks without dose adjustments prior to randomisation (Visit 3)].
• Patients must have an glycosylated Haemoglobin of 7.0% (53 millimoles per mole) to 10.0% (86 millimoles per mole) at the first visit (Screen).
• Patients must have a Body Mass Index of 45 kilogram/meter squared or less at the Screen Visit.
• In the investigator's opinion, patients must be reliable, compliant, and agree to cooperate with all planned future trial evaluations as explained in detail during the informed consent process and to be able to perform them.

Exclusion criteria:

• Impaired cognitive ability as supported by the Saint Louis University Mental Status Examination, additional assessment if necessary, and verified by the investigator at the Screen Visit.
• Depressed mood as supported by a score of 10 or more on the Patient Health Questionnaire at the Screen Visit.
• Type 1 Diabetes Mellitus as determined by past medical records and history.
• Acute coronary syndrome (non-ST Elevation Myocardial Infarction, ST Elevation Myocardial Infarction, and/or unstable angina pectoris), stroke or transient ischemic attack within 3 months prior to Screen Visit.
• Indication of liver disease determined during Screen and/or Run-In Period, defined by a serum level above 3 times the upper limit of normal in any of the following: alanine aminotransferase, aspartate aminotransferase, or alkaline phosphatase.
• Bariatric, gastric bypass, and other gastrointestinal procedures or surgeries (including all types of gastric banding, restriction, and/or LapBand) with the objective of promoting weight loss within the past two years at Screen Visit.
• Medical history of cancer (except for resected non-invasive basal or squamous cell carcinoma) and/or treatment for cancer within the last 5 years.
• Blood dyscrasias or any disorders causing hemolysis or unstable red blood cells (malaria, babesiosis, haemolytic anaemia).

Boehringer Ingelheim (BI) acknowledges that investigators have the right to publish the study results. Investigators shall provide BI with a copy of any publication or presentation for review prior to any submission. Such review will be done with regard to proprietary information, information related to patentable inventions, medical, scientific, and statistical accuracy within 60 days. BI may request a delay of the publication in order to protect BI's intellectual property rights.