Background:Infections are an important cause of morbidity and mortality in older people; however, they are often difficult to diagnose because the signs and symptoms of infection in older people are frequently atypical. Fever, one of the most important signs of infection, is a case in point. Preliminary evidence suggests that the febrile response in older persons is blunted, leading to the clinical maxim, “the older, the colder.” The objective of this study was to assess the effect of age on the febrile response to moderate-to-severe pneumonia in hospitalized patients adjusted for the effect of anatomic site at which the temperature was measured.Methods:This is a retrospective cohort study of 320 hospitalized patients with moderate-to-severe pneumonia. The study was designed to assess the effect of age on the febrile response to moderate-to-severe pneumonia in hospitalized patients, adjusting for the effect of the anatomic location of the temperature measurement. The highest temperature of each day and the anatomic sites at which temperatures were taken (axillary, oral, rectal, or other) on days 1 and 2 of infection and at hospital discharge. Baseline demographic information, including age, were obtained for each patient.Results:There were 320 patients (median age, 64 years; range, 18–97 years). Using a linear regression model, significant inverse correlations were found between age and the temperature for patients on the first and second days of hospitalization (P< 0.001). For each decade increase in age, the average temperature on the first 3 days of infection was lower by 0.15°C. Temperature at discharge, a surrogate for baseline temperature, also decreased at an equal rate with age.Conclusion:In this study, the febrile response to infections was reduced with increasing age and baseline temperatures were generally lower in older patients.