| Study | N | Follow-up | Dose mGy | Results and notes |
| Grosshans et al. 2007 [52] | 37 | Mean = 23 months | 25,000 | Progressive cognitive decline reported in lung cancer patients given prophylactic cranial irradiation but 41% had significant cognitive deficit at start, probably due to earlier lung radiation exposures. Mean age 59. Post cranial irradiation cognitive deficits were seen (p < 0.008) but were discarded by study as due to development of the lung cancer. |
| Tucker et al. 1989 [51] | 24 | At 12 years post exposure | 24,000 | NHL and leukemia adult patients. Mean age 39. Long term neuro-psychological consequences found in 38%. (p < 0.02) Objective neurological changes (p < 0.02). Significant moderate brain atrophy. Significant EEG anomalies. |
| Peper et al. 2000 [53] | 12 | 8.8y | 14,000 | Whole body irradiation for bone marrow transplant. Increase in brain atrophy found. Few statistically significant long-term neurobiological effects: logical memory, verbal encoding, small sample. |
| Nieder et al. 1999 [54] | 49 | 4 - 130 months Mean = 10 m | 30,000 | Whole body irradiation. Non-reversible symptoms found; lassitude, distractibility, memory impairment (80% of patients) personality change, one case of progressive dementia. CT changes in 81% of patients 2 years after irradiation. Cerebral atrophy in 51% of patients. |
| Frytak et al. 1989 [55] | 283 | >1.5 y | 30,000 | Prophylactic cranial irradiation for small cell lung cancer. Neurological effects including dementia in 37% of survivors. PCI associated with unacceptable level of neurotoxicity. |
| Schulte et al. 1996 [56] | 63,825 | Death certs | <50 mSv | Death certificate by occupation. Highest ranking for Alzheimers dementia for female radiology technicians. |
| Wilkinson et al. 2000 [57] | 67,960 | Death Certs | <50 mSv | Nuclear workers. RR 1.46 compared with national population for mortality from dementia. |
| Sibley et al. 2003 [58] | 67,960 | Death certs | <50 mSv | Nuclear workers. Significant excess risk (discussed in this report). Internal exposures. |
| Sibley et al. 2006 [59] | 67,960 | Death certs | <50 mSv | Nuclear workers. Significant excess risk (discussed in this report). Internal exposures. |
| Loganovsky 2009 [60] | Chernobyl workers | EEG |
| Significant neurological effects reported. Internal exposures. |
| Johnson et al. 1985 [61] | N = 20 | 6.2 | 30 Gy cranial | 75% had abnormal CT scans; 75% had neurological complaints; 65% had abnormal neuropsychiatric issues. |
| Begum et al. 2012 [5] | review |
|
| Concluded that mechanistic evidence favours a causal association. |
| Marazitti et al. 2014 [62] | review |
|
| Radiation exposure leads to an increased risk of neurodegenerative effects. Brain is now recognised as one of the main dose-limiting organs in radiotherapy” |