@article {Whibleye036219,
	title = {Sleep disturbance as a moderator of the association between physical activity and later pain onset among American adults aged 50 and over: evidence from the Health and Retirement Study},
	journal = {BMJ Open},
	volume = {10},
	year = {2020},
	pages = {e036219},
	abstract = {Objective To examine whether sleep disturbance modifies the association between physical activity and incident pain.Design Prospective population-based study.Setting Health and Retirement Study.Participants American adults aged >=50 years who reported no troublesome pain in 2014 were re-assessed for pain in 2016. Of 9828 eligible baseline respondents, 8036 (82\%) had complete follow-up data for adjusted analyses (weighted analysis population N=42 407 222).Exposures Physical activity was assessed via interview with questions about time spent in moderate and vigorous physical activity. Sleep disturbance, assessed using a modified form of the Jenkins Sleep Scale, was examined as a potential moderator.Main outcome measure Troublesome pain.Results In weighted analyses, 37.9\% of the 2014 baseline pain-free sample participated in moderate or vigorous physical activity once a week or less, with an overall mean Physical Activity Index Score of 9.0 (SE=0.12). 18.6\% went on to report troublesome pain in 2016. Each one-point higher on the Physical Activity Index Score was associated with a reduced odds ratio (OR) of incident pain for those who endorsed sleep disturbance never/rarely (OR=0.97, 95\% CI 0.94 to 0.99), but not for those who endorsed sleep disturbance sometimes (OR=0.99, 95\% CI 0.97 to 1.01) or most of the time (OR=1.01, 95\% CI 0.99 to 1.03). The analysis of possible interaction demonstrated that frequency of sleep disturbance moderated the physical activity and incident pain association (Wald test: p=0.02).Conclusions The beneficial association of physical activity on reduced likelihood of later pain was only observed in persons who endorsed low levels of sleep disturbance.},
	keywords = {pain, Physical activity, sleep disorders},
	issn = {2044-6055},
	doi = {10.1136/bmjopen-2019-036219},
	author = {Whibley, Daniel and Heidi M Guyer and Swanson, Leslie M and Braley, Tiffany J and Kratz, Anna L and Galit L Dunietz}
}
@article {5954,
	title = {Documentation of Biomarkers in the 2006 and 2008 Health and Retirement Study},
	year = {2013},
	institution = {Institute for Social Research, University of Michigan},
	address = {Ann Arbor, Michigan},
	abstract = {Biomarkers refer to the general range of physiological, metabolic, biochemical, endocrine and genetic measures that can be obtained in living organisms. The term is most commonly used to refer to one-time biochemical or hematological measures made on blood or other available bodily fluids, but perhaps the term should be used for a broader range of measures. In 2006 and 2008, HRS included the following biomarkers measurements, administered in this order: Saliva collection for DNA extraction; Blood spot collection for cholesterol, hemoglobin A1C, CRP and cystatin C analysis (results for C-reactive protein and cystatin C are forthcoming). This report describes the following for each of the measures listed above: Rationale and key citations; Sample description; Measure  description; Equipment; Protocol description; Special instructions.},
	keywords = {Health Conditions and Status, Healthcare, Methodology},
	author = {Eileen M. Crimmins and Jessica Faul and Jung K Kim and Heidi M Guyer and Kenneth M. Langa and Mary Beth Ofstedal and Amanda Sonnega and Robert B Wallace and David R Weir}
}
