Prostate, UTIs etc. Commonly prostate enlargement, mostly benign prostatic hypertrophy which comes with age, also prostatitis and prostate cancer. Cystitis or urethritis including stds. Bladder stone. Caffeine & high fluid intake. Anxiety. Occasionally: urethral stricture, bladder diverticulum, bladder reflux, interstitial cystitis.
Prostate; diabetes. As men age, the male hormone causes the prostate gland to enlarge; since it surrounds the urethra, it can narrow this tube & press into the bladder wall & prevent complete bladder emptying; thus the man feels the urge to pee more often & urgently. One of the signs of diabetes is urinary frequency. Urinary tract infections (uncommon in men) are possible cause too. See doc for eval for these issues.