Preterm birth, also known as premature birth, is the birth of a baby at fewer than 37 weeks gestational age, as opposed to full-term delivery at approximately 40 weeks. Extreme preterm is less than 28 weeks, very early preterm birth is between 28 and 32 weeks, early preterm birth occurs between 32 and 36 weeks, late preterm birth is between 34 and 36 weeks gestation. These babies are also known as premature babies or colloquially preemies (American English) or premmies (Australian English). Symptoms of preterm labor include uterine contractions which occur more often than every ten minutes and/or the leaking of fluid from the vagina before 37 weeks. Premature infants are at greater risk for cerebral palsy, delays in development, hearing problems and problems with their vision. The earlier a baby is born, the greater these risks will be.The cause of spontaneous preterm birth is often not known. Risk factors include diabetes, high blood pressure, multiple gestation (being pregnant with more than one baby), being either obese or underweight, vaginal infections, air pollution exposure, tobacco smoking, and psychological stress. For a healthy pregnancy, medical induction of labor or cesarean section are not recommended before 39 weeks unless required for other medical reasons. There may be certain medical reasons for early delivery such as preeclampsia.Preterm birth may be prevented in those at risk if the hormone progesterone is taken during pregnancy. Evidence does not support the usefulness of bed rest.
Likewise the hypothesis is, that as infants go through states of cognitive development, people with Alzheimers disease go through the reverse process of progressive cognitive impairment.The association with celiac disease is unclear, with a 2019 study finding no increase in dementia overall in those with CD, while a 2018 review found an association with several types of dementia including Alzheimers disease. Pathophysiology
Neuropathology
Alzheimers disease is characterised by loss of neurons and synapses in the cerebral cortex and certain subcortical regions. This loss results in gross atrophy of the affected regions, including degeneration in the temporal lobe and parietal lobe, and parts of the frontal cortex and cingulate gyrus. Degeneration is also present in brainstem nuclei particularly the locus coeruleus in the pons. Studies using MRI and PET have documented reductions in the size of specific brain regions in people with Alzheimers disease as they progressed from mild cognitive impairment to Alzheimers disease, and in comparison with similar images from healthy older adults.Both Aβ plaques and neurofibrillary tangles are clearly visible by microscopy in brains of those with Alzheimers disease, especially in the hippocampus. However, Alzheimers disease may occur without neurofibrillary tangles in the neocortex. Plaques are dense, mostly insoluble deposits of beta-amyloid peptide and cellular material outside and around neurons. Tangles (neurofibrillary tangles) are aggregates of the microtubule-associated protein tau which has become hyperphosphorylated and accumulate inside the cells themselves.