You're welcome, JPK58. Glad to be of help.
By "AGE" I'm assuming you mean a persons age in years. I don't believe age has anything to do with Janumet's "effectiveness" but age has a larger role with renal function. To make it clear for other readers, Janumet is combination of two drugs; Sitagiptin and Metformin.
This a brief from the Merck web site - makers of Janumet - Section 8.5 - Geriatric Use JANUMET.
"Because Sitagiptin and Metformin are substantially excreted by the kidney, and because aging can be associated with reduced renal functions, JANUMET should be used with caution as age increases. Care should be taken in dose selection ans should be based on careful and regular monitoring of renal function.
Of the total number of subjects [N=3884] in Phase II and III clinical studies of Sitagliptin, 725 patients were 65 years and over, while 61 patients were 75 years and older. No overall differences in safety or effectiveness were observed between subjects 65 years and over and younger subjects. While this and other clinical experience have not identified differences in responses between the elderly and younger patients, greater sensitivity of some older individuals cannot be ruled out.
Metformin hydrochloride - The initial and maintenance dosing of Metformin should be conservative in patients with advanced age, due to the potential for decreased renal function in this population."
Since Merck does not provide a clear understanding of dosage for the elderly you need to discuss this with your care provider and whether continuing with Janumet is appropriate for you. Hope this answers your question.