Weaker and more fragmented circadian rhythms in the elderly are associated with an increased risk of dementia, prospective data have shown.1 A meta-analysis found no significant association between menopausal hormone therapy and dementia.[Disruption of circadian rhythms by nighttime light causes a phase shift and suppression of the amplitude of the central circadian pacemaker.1 Such disruption has been associated with metabolic syndrome, diabetes, obesity, heart attack, stroke, and hypertension.[Disrupted circadian rhythms predict a higher risk of mortality, accounting for age, gender, and lifestyle."[1] Sleeping in dim light for one night increases blood sugar and heart rate.[2] Sleep deprivation increases beta-amyloid levels, which are associated with Alzheimer's disease and impaired brain function.[3] Light smog may increase the risk of Alzheimer's disease.