Table 2.

Number of hits in the area of sleep monitoring systems research between 2010 and 2020.

Keywords	Web of Science	PubMed	IEEE Xplore
Monitor elderly	8700	120,291	2998
Elderly monitoring system	3545	22,742	2421
Monitoring technology	213,286	95,162	116,056
Long term elderly monitor	891	8858	205
Smart home	15,545	1101	13,497
Monitoring system	345,087	131,532	189,744
Health monitoring	256,174	177,388	31,965
Monitoring technology	213,286	95,162	116,056
User behavior	82,881	16,103	28,829
Elderly People Living Alone	877	4449	229
Activity recognition	56,194	49,094	12,687
Activity daily living	29,382	64,711	2589
Changing behavior in elderly	2333	91,998	117
Unobtrusive Activity Recognition	202	54	133
Mobility in smart house	140	12	62
Monitor mobility in elderly	372	1377	156
Daily mobility	8180	7926	1018
Daily mobility in elderly	1073	5135	86
Social isolation	17,026	17,947	538
Loneliness	10,501	5321	125
Social Isolation in the elderly	741	6711	42
Limit social isolation	1661	2144	39
Limit social isolation in elderly	71	850	1
Taking meals	4227	514	194
Monitor eating in elderly	66	1027	20
Eating Activity	16,859	18,186	346
Eating Activity in elderly	321	5266	21
Nutrition in elderly	10,593	9044	33
Malnutrition in elderly	2314	1893	6
Smart sensing	21,915	2694	13,830
Non-intrusive sensor	1186	173	898
Unobtrusive sensors	1296	529	1112
Wireless sensor	89,018	6251	116,392
User privacy	24,957	1109	18,278
User acceptance	17,489	4621	4199
User satisfaction	19,825	3240	6434
Elderly monitoring data processing	623	3860	576
Elderly monitoring big data	119	203	79
Elderly monitoring data mining	91	227	95
Elderly monitoring machine learning	252	747	273
Elderly monitoring artificial intelligence	177	1065	414