Population normative data for three cognitive screening tools for older adults in sub-Saharan Africa

Gray, William Keith; Paddick, Stella-Maria; Ogunniyi, Adesola; Olakehinde, Olaide; Dotchin, Catherine; Kissima, John; Urasa, Sarah; Kisoli, Aloyce; Rogathi, Jane; Mushi, Declare; Adebiyi, Akindele; Haule, Irene; Robinson, Louise; Walker, Richard

doi:10.1590/1980-57642021dn15-030005

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Original Article • Dement. neuropsychol. 15 (03) • Jul-Sep 2021 • https://doi.org/10.1590/1980-57642021dn15-030005 linkcopy

Population normative data for three cognitive screening tools for older adults in sub-Saharan Africa

Dados normativos populacionais para três instrumentos de triagem cognitiva para idosos na áfrica subsaariana

Authorship SCIMAGO INSTITUTIONS RANKINGS

ABSTRACT

In sub-Saharan Africa (SSA),cognitive screening is complicated by both cultural and educational factors, and the existing normative values may not be applicable. The Identification of Dementia in Elderly Africans (IDEA) cognitive screen is a low-literacy measure with good diagnostic accuracy for dementia.

Objective: The aim of this study is to report normative values for IDEA and other simple measures [i.e., categorical verbal fluency, the Consortium to Establish a Registry for Alzheimer’s Disease (CERAD) 10-word list] in representative community-dwelling older adults in SSA.

Methods: Individuals aged ≥60 years resident in 12 representative villages in Kilimanjaro, Tanzania and individuals aged ≥65 years resident within three communities in Akinyele Local Government Area, Oyo State, Nigeria underwent cognitive screening. The normative data were generated by the categories of age, sex, and education.

Results: A total of 3,011 people in Tanzania (i.e., 57.3% females and 26.4% uneducated) and 1,117 in Nigeria (i.e., 60.3% females and 64.5% uneducated) were screened. Individuals with higher age, lower education, and female gender obtained lower scores. The 50th decile values for IDEA were 13 (60–64 years) vs. 8/9 (above 85 years), 10–11 uneducated vs. 13 primary educated, and 11/12 in females vs. 13 in males. The normative values for 10-word list delayed recall and categorical verbal fluency varied with education [i.e., delayed recall mean 2.8 [standard deviation (SD) 1.7] uneducated vs. 4.2 (SD 1.2) secondary educated; verbal fluency mean 9.2 (SD 4.8) uneducated vs. 12.2 (SD 4.3) secondary educated], substantially lower than published high-income country values.

Conclusions: The cut-off values for commonly used cognitive screening items should be adjusted to suit local normative values, particularly where there are lower levels of education.

Keywords: cognition; screening; Tanzania; Nigeria; sub-Saharan Africa; education

Tanzania	10th	20th	30th	40th	50th	60th	70th	80th	90th
Age
60–64 years (n=775)	10	11	12	13	13	14	14	15	15
65–69 years (n=662)	9	11	12	12	13	13	14	14	15
70–74 years (n=513)	7	9	10	11	12	13	13	14	15
75–79 years (n=437)	6	8.6	10	11	12	12	13	14	14
80–84 years (n=299)	4	6	8	9	10	11	12	13	14
85 years and above (n=365)	0.6	4	5.8	7	8	10	11	13	14
Sex
Female (n=1,726)	5	8	10	11	12	13	13	14	15
Male (n=1,285)	7	10	11	12	13	13	14	14	15
Education
No formal education (n=794)	3	6	7	9	10	11	12	13	14
1–4 years of primary school (n=1,033)	7	9	10	11	12	13	13	14	15
5–7 years of primary school (n=1050)	9	11	12	13	13	14	14	14.8	15
Secondary school or higher (n=142)	11	13	13	14	14	15	15	15	15

Nigeria	20th	30th	40th	50th	60th	70th	80th	90th
Age
65–69 years (n=378)	8	10	11	12	13	13	14	15	15
70–74 years (n=240)	7	9	10	12	12	13	14	15	15
75–79 years (n=139)	6	8	9	10	11	12	13	14	15
80–84 years (n=173)	4	6	8	10	11	12	13	14	15
85 years and above (n=159)	3	5	7	8	9	10	12	13	14
Sex
Female (n=674)	5	7	9	10	11	12	13	14	15
Male (n=443)	8	10	11	12	13	13	14	15	15
Education
No formal education (n=721)	5	7	8.6	10	11	12	13	14	15
1–4 years of primary school (n=147)	8	10	11	12	12	13	14	14	15
5–7 years of primary school (n=161)	9	11	12	13	13	14	15	15	15
Secondary school or higher (n=88)	10	12	13	13	14	14.4	15	15	15

Sex	Age	No formal education					Formal education
Sex	Age	Number	20th	40^th	60th	80th	Number	20th	40th	60th	80th
Females	60–64 years	85	8	11	12	14	389	12	13	14	15
	65–69 years	237	8	11	12	14	347	11	12	13	15
	70–74 years	208	7	9	12	14	198	9	11	13	14
	75–79 years	188	6	9	11	13	149	9	11	13	14
	80–84 years	196	5	8	11	12	91	7	9	12	14
	85 years and above	247	3	6	9	12	65	4	7	9.6	13
Males	60–64 years	19	6	8	12	14	310	12	13	14	15
	65–69 years	50	9	11	13	14.8	366	11	13	14	15
	70–74 years	57	9.6	12	13	15	290	10	12	13	15
	75–79 years	55	7	10	12	14	184	10	12	13	14
	80–84 years	55	5.2	8.4	11	13.8	130	8	10	13	14
	85 years and above	110	5	8.4	11	14	102	6.6	9	12	14

CERAD immediate recall word list-learning
Sex	Age	No formal education					Formal education
Sex	Age	Number	20^th	40th	60th	80th	Number	20th	40th	60th	80th
Females	60–64 years	85	9	12	14	18	389	12	14	16	19
	65–69 years	237	12	14	16	18	347	11	13	16	19
	70–74 years	208	10	12	15	17	198	10	12	14	17
	75–79 years	188	8	11	13	16	149	10	12	14	17
	80–84 years	196	7	11	13	16	91	6	10	13	17
	≥85 years	247	5	9	11.6	15	65	3.8	8	11	16
Males	60–64 years	19	8	9.2	10.8	13.2	310	13	14	16	18
	65–69 years	50	11	14.6	18	20	366	12	14	16	19
	70–74 years	57	10	12.4	15	18	290	11	13	15	18
	75–79 years	55	9	12	13.4	15.2	184	10	12	14	16
	80–84 years	55	7.8	11	14	16	130	8.8	11	13	17
	≥85 years	110	5.8	12	13	16	102	7	10	13	15

CERAD delayed word-list recall
	Age	No formal education					Formal education
	Age	Number	20^th	40th	60th	80th	Number	20th	40th	60th	80th
Females	60–64 years	85	2	3	4	5	389	3	4	5	6
	65–69 years	237	2	3	4	5	347	3	4	5	6
	70–74 years	208	2	3	4	5	198	2	3	4	5
	75–79 years	188	1	2	3	5	149	2	3	4	5
	80–84 years	196	1	2	3	5	91	0	2	3	4
	≥85 years	247	0	1	3	4	65	0	1	3	4
Males	60–64 years	19	1	3	3	5	310	3	4	5	6
	65–69 years	50	2	4	5	6	366	3	4	5	6
	70–74 years	57	2	3	4	5	290	2	4	4	5
	75–79 years	55	1	3	4	5	184	2	3	4	5
	80–84 years	55	1	3	4	5	130	1	2	4	5
	≥85 years r	110	0	2.4	3.6	5	102	0	2	3	5

Categorical verbal fluency – Animal naming
	Age	No formal education					Formal education
	Age	Number	20^th	40th	60th	80th	Number	20th	40th	60th	80th
Males	60–64 years	85	4	7	9	13	389	8	9	11	13
	65–69 years	237	6	8	10	13	347	7.6	9	10	13
	70–74 years	208	6	9	10	13	198	6	8	10	12
	75–79 years	188	5	7	9	12	149	6	8	10	12
	80–84 years	196	5	7	9	11.6	91	5	7	8.2	10.6
	≥85 years	247	4	6	8	11	65	4	6	8	10
	60–64 years	19	3	7	9	14	310	8	10	12	15
	65–69 years	50	7	9	12	15.8	366	8	10	12	15
	70–74 years	57	6	10	12.8	16	290	8	10	12	15
	75–79 years	55	6.2	9.4	12	15	184	7	10	11	12
	80–84 years	55	6	8	10	15	130	7	8.4	10	13
	≥85 years	110	5	8	10	15.8	102	5	9	10	13

Education level	Sex	Age	Recall first trial		Recall second trials		Recall third trials		Animal naming		Delayed word-list recall
Education level	Sex	Age	Mean	SD	Mean	SD	Mean	SD	Mean	SD	Mean	SD
No formal schooling	Females	60–64 years	3.7	2.006	4.7	1.983	4.8	2.069	8.8	5.794	3.4	2.078
		65–69 years	4.1	1.616	5.0	1.618	5.5	1.517	9.8	4.514	3.7	1.759
		70–74 years	3.8	1.710	4.5	1.636	5.1	1.818	9.9	4.156	3.3	1.817
		75–79 years	3.4	1.792	4.1	1.802	4.5	1.902	8.6	3.993	3.0	1.917
		80–84 years	3.2	1.931	4.0	1.951	4.2	2.079	8.3	4.284	2.8	1.955
		85 years and above	2.6	1.769	3.4	2.048	3.8	2.371	7.5	4.695	2.2	2.100
	Males	60–64 years	2.9	2.079	3.3	2.077	3.9	1.985	8.9	5.547	2.8	1.951
		65–69 years	4.4	2.090	5.3	1.906	5.6	2.260	11.1	5.211	4.1	2.165
		70–74 years	3.8	1.722	4.8	1.575	5.4	1.811	11.4	5.357	3.7	1.901
		75–79 years	3.6	1.470	4.4	1.532	4.5	1.824	10.9	4.550	3.3	2.082
		80–84 years	3.2	1.663	4.0	1.915	4.4	2.224	9.7	5.041	3.2	2.035
		85 years and above	3.0	1.812	4.0	2.250	4.2	2.362	9.8	5.674	2.9	2.042
Formal schooling	Females	60–64 years	4.2	1.717	5.3	1.628	5.9	1.694	10.6	4.126	4.4	1.838
		65–69 years	4.0	1.685	5.2	1.684	5.6	1.866	10.0	3.677	4.3	1.990
		70–74 years	3.7	1.699	4.7	1.859	5.2	1.969	9.3	3.731	3.6	1.882
		75–79 years	3.6	1.725	4.4	1.673	4.8	1.789	9.0	3.892	3.4	1.838
		80–84 years	3.1	1.945	3.9	2.152	4.2	2.489	7.8	3.543	2.6	1.982
		85 years and above	2.5	2.078	3.5	2.278	3.8	2.622	7.2	4.680	2.2	2.101
	Males	60–64 years	4.1	1.536	5.3	1.358	5.9	1.530	11.8	4.333	4.4	1.682
		65–69 years	4.1	1.712	5.3	1.568	5.9	1.646	11.7	4.513	4.3	1.764
		70–74 years	3.7	1.748	4.9	1.768	5.4	1.864	11.5	5.160	3.8	1.898
		75–79 years	3.4	1.709	4.6	1.509	4.9	1.691	10.2	3.679	3.5	1.771
		80–84 years	3.3	1.857	4.3	1.948	4.6	2.300	9.9	4.588	3.1	2.106
		85 years and above	3.1	1.908	3.7	2.093	4.1	2.254	9.2	4.599	2.6	2.058

		Parameter estimate	Lower 95%CI	Upper 95%CI	Significance
Recall first trial	Age	-0.049	-0.055	-0.043	<0.001
	Male	0.079	-0.035	0.192	0.173
	Formal schooling	0.014	-0.109	0.137	0.823
Recall second trial	Age	-0.058	-0.064	-0.052	<0.001
	Male	0.177	0.063	0.292	0.002
	Formal schooling	0.184	0.059	0.308	0.004
Recall third trial	Age	-0.066	-0.073	-0.059	<0.001
	Male	0.158	0.034	0.283	0.013
	Formal schooling	0.264	0.129	0.399	<0.001
Animal naming	Age	-0.092	-0.107	-0.076	<0.001
	Male	1.656	1.369	1.943	<0.001
	Formal schooling	0.178	-0.134	0.490	0.263
Delayed recall	Age	-0.063	-0.070	-0.056	<0.001
	Male	0.209	0.085	0.332	0.001
	Formal schooling	0.300	0.165	0.434	<0.001

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[TFN1] Bold values represent deciles.