Low-grade gliomas (LGG) are slow-growing primary brain tumors that typically affect young adults. Advanced age is widely recognized as a poor prognostic factor in LGG. The impact of age on postoperative outcome in this patient group has not been systemically studied.We performed a nationwide register-based study with data from the Swedish Brain Tumor Registry (SBTR) for all adults diagnosed with a supratentorial LGG (WHO grade II astrocytoma, oligoastrocytoma, or oligodendroglioma) during 2005-2015. Patient- and tumor-related characteristics, postoperative complications, and survival were compared between three different age groups (18-39 years, 40-59 years, and ≥60 years).We identified 548 patients; 204 patients (37.2%) aged 18-39 years, 227 patients (41.4%) aged 40-59 years, and 117 patients (21.4%) ≥60 years of age. Unfavorable preoperative prognostic factors (eg, functional status and neurological deficit) were more common with increased age (P < .001). In addition, overall survival was significantly impaired in those 60 years and above (P < .001). We observed a clear dose-response for age with separation of survival curves at 50 years. Biopsy was more common in patients ≥60 years (P < .001). Subgroup analysis of patients with resection revealed a higher amount of postoperative neurological deficits in older patients (P = .029).In general, older patients with LGG have several unfavorable prognostic factors compared with younger patients but seem to tolerate surgery in a comparable fashion. However, more neurological deficits were observed following resections in elderly. Our data further support a cutoff at 50 years rather than 40 years for selection of high-risk patients.