Characteristics of 51 studies included in the meta-analysis
| First author, year * | Design, cohort name, country | Observation | Sample for analysis/cases | Mean age; female | Outcome | Type of sleep disorders |
| Suh, 2018 | South Korea | 4y (max) | 2,238/265 | 68.1; 54% | Cognitive decline | Sleep characteristics |
| Sindi, 2018 | Sweden | 9y (max) | 437/19 | 70; 60% | Dementia | Insomnia and sleep duration |
| Sweden | 9y (max) | 306/122 | 83.9; 85% | |||
| Finland | 21y (mean); 26y (max) | 1,409/61 | 50.2; 62% | |||
| 10y (mean) | 703/44 | 70.2; 65% | ||||
| Ohara, 2018 | Japan | 8.8y (mean); 10y (max) | 1,497/294 | 70; 56% | Dementia | Sleep duration |
| Nakakubo, 2018 | Japan | 4y (max) | 2,096/280 | 71; 53% | Cognitive decline | Sleep duration; excessive daytime sleepiness |
| Lysen, 2018 | Netherlands | 8.5y (mean) | 4,835/420 dementia (320 AD) | 71.9; 58% | Dementia; AD | Sleep quality; PSQI components |
| Lutsey, 2018 | USA | 14.9y (median); 17.5y (max) | 1,083 for apnoea; 1,653 for sleep duration/145 | 62.7; 53% | Dementia | Apnoea; sleep duration |
| Lu, 2018 | Japan | 5.7y (mean) | 7,422/688 | 74.7; 56% | Dementia | Sleep duration |
| Li, 2018 | USA | 11y (max); 4.6y (mean) | 1,097/220 | 81.0; 77% | AD | Sleep quality |
| 11y (max); 3.4 (mean) | 855/344 | 80.1; 79% | MCI | |||
| Li, 2018 | USA | max >30y | 2,461/227 | 51; 50% | Dementia | Sleep duration |
| Larsson, 2018 | Sweden | 12.6y (mean) | 28,775/3,755 | 71.6; 47% | AD | Sleep duration |
| Burke, 2018 | USA | 4.24y (mean) | 9,184/361 | 71; 65% | Probable AD | Sleep disturbance |
| Westwood, 2017 | USA | 10y (max) | 2,457/234 dementia (181 AD) | 72; 57% | Dementia; AD | Sleep duration |
| Sung, 2017 | China-Taiwan | 10y (max) | 184,158/5,301 | 49; 65% | Dementia | Nonapnoea sleep disorders |
| Chang, 2013 | China-Taiwan | 4.78 to 4.93y (mean) | 8,484/199 | Mixed; 41% | Dementia | Sleep apnoea |
| Reijs, 2017 | Finland | 2.4y (mean) | 353/na | 70.6; 59% | AD | Sleep problem |
| Pase, 2017 | USA | 12y (mean); 19y (max) | 321/32 dementia (24 AD) | 67; 50% | Dementia; AD | Percentage of REM sleep |
| Luojus, 2017 | Finland | 21.9y (mean) | 2,386/287 dementia (234 AD) | 53; 0% | Dementia; AD | Sleep disturbance |
| Gabelle, 2017 | France | 1y (max) | 479/63 | 74; 68% | Cognitive decline | Sleep characteristics |
| Bokenberger, 2017 | Sweden | 17.7y (max); 14.3y (median) | 11,247/1,844 | 72.5; na | Dementia | Sleep characteristics |
| Niu, 2016 | China | 1y (max) | 1,010/161 | 69.8; 65% | Cognitive decline | Sleep characteristics |
| Ding, 2016 | USA/Canada | 5.7y (mean) | 7,547/310 | 67.5; 0% | Dementia | Sleep apnoea |
| Diem, 2016 | USA | 4.9y (mean) | 1,245/290 MCI and 183 dementia | 82.6; 100% | Dementia or MCI | Sleep characteristics |
| Yaffe, 2011 | USA | 4.7y (mean) | 298/60 MCI and 47 dementia | 82.3; 100% | Dementia or MCI | Sleep characteristics |
| Chen, 2016 | USA | 7.3–7.7 (mean) | 7,444/802 | 70.1; 100% | Cognitive decline | Sleep duration |
| Yaffe, 2015 | USA | 8y (max) | 179,738/21,784 dementia (4,107 AD and 2,715 VD) | 66.9–68.5; 0% | Dementia and its subtypes | Series of sleep problems |
| Tsapanou, 2015 | USA | 3y (max) | 1,041/78 | 79.3; 69.8% | Dementia | Series of sleep problems |
| Martin, 2015 | France | 7.8y (mean) | 559/na | 67.0; 60.3% | Attentional decline | SBD |
| Lin, 2015 | China-Taiwan | 5y (max) | 3,020/166 | Mixed; 43.7% | Dementia and its subtypes | Sleep-related movement disorders |
| Chiu, 2015 | China-Taiwan | 7y (max) | 5,960/88 | Mixed; 49% | Dementia | Insomnia |
| Song, 2015 | USA | 3.4y (mean) | 2,601/484 | 76.0; 0% | Cognitive decline | Sleep stage duration |
| Blackwell, 2015 | USA | 3.4y (mean) | 2,636/484 | 76.0; 0% | Cognitive decline | SBD |
| Blackwell, 2014 | USA | 3.4y (mean) | 2,822/484 | 76.0; 0% | Cognitive decline | Sleep characteristics |
| Benedict, 2015 | Sweden | 40y (max) | 1,574/270 dementia (119 pure AD and 61 VD) | 49.6; 0% | Dementia and its subtypes | Sleep disturbances |
| Hahn, 2014 | Sweden | 9y (max) | 214/61 dementia (47 AD) | 83.4; 80.4% | Dementia and its subtypes | Sleep pattern change |
| Virta, 2013 | Finland | 22.6y (mean) | 1,326/179 | Midlife; 47.9% | AD | Sleep characteristics |
| Sterniczuk, 2013 | 12 countries in Europe | 4.3y (mean) | 17,656/300 | 63.9; 55.5% | Dementia | Sleep characteristics |
| Peters, 2013 | USA | 3.3y (mean) | 230/61 dementia (47 AD) | 81.9; 50% | Dementia and its subtypes | Nighttime behaviours |
| Lim, 2013 | USA | 6y (max); 3.3y (mean) | 737/97 | 81.6; 76% | AD | Sleep fragmentation |
| Benito-Leon, 2013 | Spain | 3.4y (mean) | 2,715/na | 72.9; 57% | Cognitive decline | Sleep duration |
| Benito-León, 2009 | Spain | 3.2y (median) | 3,286/140 | 72.9; 57% | Dementia and its subtypes | Sleep duration |
| Potvin, 2012 | Canada | 1y (max) | 1,664/68 women+37 men | 74.4; 69.7% | Cognitive decline | Sleep characteristics |
| Keage, 2012 | Canada | 10y (max) | 604/na | 75; 53% | Cognitive decline | Sleep characteristics |
| Jaussent, 2012 | France | 8y (max) | 4,898/697 | Range=65–85; 57% | Cognitive decline | Sleep characteristics |
| Boot, 2012 | USA | 3.8y (median) | 651 at least one follow-up/104 | 77; 30% | MCI | RBD |
| Osorio, 2011 | USA | 7.7y (mean) | 346/25 | Range: 24–96; 64% | AD | Insomnia |
| Elwood, 2011 | UK | 10y (max) | 1,225/49 AD and 44 VD | 61.5; 0% | AD and VD | Sleep characteristics |
| Lobo, 2008 | Spain | 2y (max) | 3,244/82 dementia (47 AD and 208 MCI) | 73.6; 55.2% | Dementia; AD; MCI | Sleep problems |
| Tworoger, 2006 | USA | 1.8y (mean) | 1,844/na | 74; 100% | Cognitive decline | Sleep characteristics |
| Foley, 2001 | USA | 3y (max) | 2,346/191 | 76.6; 0% | Dementia | Sleep characteristics |
| 2,242/482 | Cognitive decline | |||||
| Cricco, 2001 | USA | 3y (max) | 2,429/619 | 72; na | Cognitive decline | Insomnia |
| 4,015/1076 | ||||||
| Quesnot, 1999 | France | 4y (max) | 1,389/184 | Range: 59–71; 58.7% | Cognitive decline | Snoring and excessive daytime sleepiness |
*The full reference list can be found in online supplementary appendix 3.
AD, Alzheimer’s disease; LCI, Lower Confidence Interval; MCI, Mild Cognitive Impairment; na, Not Applicable; PSQI, Pittsburgh Sleep Quality Index; RBD, Rapid Eye Movement Sleep Behavioural Disorder; REM, Rapid Eye Movement; REMR, Robust Error Meta-regression; SBD, Sleep Breathing Disorders; UCI, Upper Confidence Interval; VD, Vascular Dementia; y, year.