title: Circadian activity rhythms and risk of incident dementia and mild cognitive impairment in older women.
abstract: OBJECTIVE
  Previous cross-sectional studies have observed alterations in activity rhythms in dementia patients but the direction of causation is unclear. We determined whether circadian activity rhythms measured in community-dwelling older women are prospectively associated with incident dementia or mild cognitive impairment (MCI).
  
  
  METHODS
  Activity rhythm data were collected from 1,282 healthy community-dwelling women from the Study of Osteoporotic Fractures (SOF) cohort (mean age 83 years) with wrist actigraphy for a minimum of three 24-hour periods. Each participant completed a neuropsychological test battery and had clinical cognitive status (dementia, MCI, normal) adjudicated by an expert panel approximately 5 years later. All analyses were adjusted for demographics, body mass index (BMI), functional status, depression, medications, alcohol, caffeine, smoking, health status, and comorbidities.
  
  
  RESULTS
  After 4.9 years of follow-up, 195 (15%) women had developed dementia and 302 (24%) had developed MCI. Older women with decreased activity rhythms had a higher likelihood of developing dementia or MCI when comparing those in the lowest quartiles of amplitude (odds ratio [OR] = 1.57; 95% CI, 1.09-2.25) or rhythm robustness (OR = 1.57; 95% CI, 1.10-2.26) to women in the highest quartiles. An increased risk of dementia or MCI (OR = 1.83; 95% CI, 1.29-2.61) was found for women whose timing of peak activity occurred later in the day (after 3:51 PM) when compared to those with average timing (1:34 PM-3:51 PM).
  
  
  CONCLUSIONS
  Older, healthy women with decreased circadian activity rhythm amplitude and robustness, and delayed rhythms have increased odds of developing dementia and MCI. If confirmed, future studies should examine whether interventions (physical activity, bright light exposure) that influence activity rhythms will reduce the risk of cognitive deterioration in the elderly.
authors.affiliation: California Pacific Medical Center Research Institute, San Francisco, CA 94107-1728, USA. gtranah@sfcc-cpmc.net
authors.forename: Gregory J
authors.initials: GJ
authors.lastname: Tranah
authors.forename: Terri
authors.initials: T
authors.lastname: Blackwell
authors.forename: Katie L
authors.initials: KL
authors.lastname: Stone
authors.forename: Sonia
authors.initials: S
authors.lastname: Ancoli-Israel
authors.forename: Misti L
authors.initials: ML
authors.lastname: Paudel
authors.forename: Kristine E
authors.initials: KE
authors.lastname: Ensrud
authors.forename: Jane A
authors.initials: JA
authors.lastname: Cauley
authors.forename: Susan
authors.initials: S
authors.lastname: Redline
authors.forename: Teresa A
authors.initials: TA
authors.lastname: Hillier
authors.forename: Steven R
authors.initials: SR
authors.lastname: Cummings
authors.forename: Kristine
authors.initials: K
authors.lastname: Yaffe
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000523:psychology*; D002940:Circadian Rhythm / Q000502:physiology*; D060825:Cognitive Dysfunction / Q000503:physiopathology / Q000523:psychology*; D015331:Cohort Studies; D003704:Dementia / Q000503:physiopathology / Q000523:psychology*; D005260:Female; D006801:Humans; D009483:Neuropsychological Tests; D012307:Risk Factors; D014930:Women / Q000523:psychology*