Why Am I Always Tired After 40? What Your Body Is Trying to Tell You

Sleep apnea is the single most commonly missed cause of persistent fatigue in men over forty. Obstructive sleep apnea, in which the airway repeatedly collapses during sleep causing brief awakenings that the person typically does not remember, is estimated to affect twenty to thirty percent of middle-aged men, the majority of whom are undiagnosed. The resulting sleep fragmentation prevents the restorative deep sleep phases from completing properly, producing daytime exhaustion regardless of total time in bed. The classic presentation is a man who sleeps what appears to be an adequate number of hours but wakes unrefreshed, is drowsy during the day, and has a partner who reports significant snoring or witnessed breathing pauses. If this description fits, a sleep study is the appropriate next investigation.

Low testosterone, as discussed earlier in this category, produces fatigue through reduced cellular energy production, reduced red blood cell production, and the motivational and mood effects of testosterone decline. It is worth testing fasting morning testosterone if fatigue is accompanied by other symptoms consistent with testosterone decline: reduced libido, increased abdominal fat, reduced muscle mass, mood changes, or reduced exercise tolerance.

Iron deficiency anaemia is less commonly considered in men than in women but does occur, particularly in men with poor dietary iron intake, gastrointestinal blood loss from chronic NSAID use or undetected gastrointestinal conditions, or very high athletic training loads. Anaemia produces fatigue through reduced oxygen-carrying capacity and is definitively diagnosed with a simple blood test.