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Apolipoprotein E4 genotype in Moroccan patients with dementia
, Hassan EL-Abid3, Marouane Mergaoui4, Loubna Khalki1, Laila Bouguenouch5
*Corresponding author: Youssef Razouqi, Interdisciplinary Laboratory of Biotechnology and Health, Neurosciences and Cellular Physiology Team, Mohammed VI Higher Institute of Biosciences and Biotechnology, Mohammed VI University of Sciences and Health (UM6SS), Casablanca, Morocco. yrazouqi@um6ss.ma
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Received: ,
Accepted: ,
How to cite this article: Razouqi Y, El Bouchikhi I, EL-Abid H, Mergaoui M, Khalki L, Bouguenouch L. Apolipoprotein E4 genotype in Moroccan patients with dementia. J Neurosci Rural Pract. 2025;16:620-4. doi: 10.25259/JNRP_349_2025
Abstract
Dementia is a complex disorder affecting older adults, and polipoprotein E (APOE)-ε4 is considered the primary genetic risk factor for its development. This ongoing study investigated the relationship between APOE genotypes, lifestyle variables, and illness severity in Moroccan patients compared with healthy controls. We conducted a case–control study, genotyping 24 patients and 23 controls for the APOE rs429358 and rs7412 polymorphisms. Diagnosis was based on the National Institute on Aging-Alzheimer’s Association criteria, with confirmation through magnetic resonance imaging and computed tomography scans. APOE-ε4 was significantly more prevalent in patients compared to the controls (P = 0.0002). Furthermore, low educational levels were strongly associated with increased dementia severity (P = 6.4E-6). Smoking was also more common in the patients with dementia (P = 0.0047). This brief report underscores the significance of APOE-ε4 as a risk factor for dementia in the Moroccan population. Expanding the study population will confirm associations, help identify additional risk factors, and guide and personalize therapeutic approaches, considering population-specific characteristics. This preliminary report forms part of an ongoing national study on genetic and lifestyle determinants of dementia in Morocco.
Keywords
Apolipoprotein E
Dementia
Education
Morocco
e4 allele
INTRODUCTION
Dementia is a neurological disorder that affects individuals aged 65 and older.[1] The condition is becoming increasingly prevalent worldwide and remains a significant global public health problem, as its incidence is set to rise as life expectancy increases.[2] A crucial aspect of dementia is the interplay between genetic and environmental factors, which manifests in wide variability of symptoms and gender-specific profiles.[3]
Apolipoprotein E (APOE), which stands for APOE, plays a key role in dementia risk, particularly in Alzheimer’s disease (AD). This is because it triggers a cascade of pathological processes, including neurotoxicity, tau protein phosphorylation, synaptic loss, and brain inflammation.[4] The APOE gene has three alleles, e2, e3, and e4, arising from rs429358 and rs7412. The e4 allele is strongly associated with an increased risk of developing dementia, linked to reducing the elimination of beta-amyloid, while a protective effect against dementia has been demonstrated for the e2 allele.[5]
Several studies across Sub-Saharan Africa (Nigeria, Ghana, and South Africa) have reported APOE e4 frequencies ranging from 10% to 30% among dementia patients, generally lower than those observed in European cohorts and in African Americans, who have been reported to carry the e4 allele at higher rates.[6-9] In North Africa, data remain limited to a few Egyptian and Tunisian studies reporting low e4 rates (<15%) and possible gene–environment modulation.[10] To the best of our knowledge, no study has yet examined APOE variants in a Moroccan dementia cohort, justifying this preliminary investigation.
At present, substantial research has been conducted on APOE polymorphisms worldwide. However, studies on non-European populations, particularly in North Africa, remain scarce.[11] This study aimed to determine the APOE polymorphisms and associated dementia risk factors within the Moroccan population, contributing to a better understanding of genetic risk for dementia in this region.
MATERIALS AND METHODS
Participants
The Local Human Ethics Committee (CE/UM6SS/12/24) authorized the community to conduct this cross-sectional study. All study steps were in accordance with the Declaration of Helsinki norms. From a community-based cohort, 24 subjects aged 55 years or older diagnosed with dementia and 23 age- and sex-matched healthy controls were selected (characterized as persons without any significant neurocognitive symptoms, diseases, or pertinent other medical history). The diagnosis of dementia was based on the National Institute on Ageing-Alzheimer’s Association (NIA-AA) criteria,[12] which combine clinical assessments with magnetic resonance imaging and computed tomography scans. Both a neurologist and psychiatrist validated the diagnosis. The Mini-Mental State Examination (MMSE)[13] evaluated the cognition of the controls, who had no history of dementia, neurodegenerative symptoms, or other neurological conditions.
Socio-demographic and clinical variables
We categorized participants into three groups based on their highest level of education: Illiterate, primary school, high school, and undergraduate or higher. A structured questionnaire was used to collect demographic data and lifestyle factors such as sex, age, and smoking habits.
DNA isolation and genotyping
DNA was extracted from the collected blood samples using the Maxwell Rapid Sample Concentrator (Maxwell® RSC) Blood DNA Kit (Promega Corporation, Madison, WI, USA) according to the manufacturer’s protocol. To specifically target the SNPs rs429358 and rs7412, which delineate the e2, e3, and e4 alleles, we performed the polymerase chain reaction (PCR) using the following designed primers: forward (5’-CGGGCACGGCTGTCCAAGGAG-3’) and reverse (3’-CACGCGGCCCTGTTCCACCAG-5’), according to the optimized standard protocol. The obtained PCR products were then sequenced using the Big Dye Terminator V1.1 Cycle Sequencing Kit (ABI Prism, Massachusetts, USA) and the Applied Biosystems 3500Dx Genetic Analyzer.
Statistical analysis
To evaluate the APOE allele frequency among the studied groups and to assess various risk factor associations, we used Fisher’s exact test for smaller group sizes and Chi-square testing for larger groups. Statistical tests were performed using the R programming environment.
Differences between categorical variables were first evaluated using Chi-square or Fisher’s exact tests, as shown in Tables 1 and 2. To estimate the independent contribution of each risk factor to dementia, a binary logistic regression was then performed including APOE e4 carriage, education level, and smoking habit as predictors.
| Feature | Dementia patients | Control group | χ2/Fisher’s exact | P-value |
|---|---|---|---|---|
| Education level (%) | χ2(2, n=47)=3.27 | 0.2 | ||
| Illiterate | 11 (46) | 5 (21.7) | ||
| Primary school | 6 (25) | 8 (34.78) | ||
| High school and beyond | 7 (29) | 10 (43.5) | ||
| Smoking habit | 15 (62) | 5 (21.74) | χ2(1, n=47)=8.19 | 0.0047* |
| APOE genotypes | Fisher’s exact | 0.0028* | ||
| ε2/ε2 | 0 | 1 | ||
| ε3/ε3 | 11 | 20 | ||
| ε4/ε4 | 2 | 0 | ||
| ε2/ε3 | 3 | 2 | ||
| ε2/ε4 | 2 | 0 | ||
| ε3/ε4 | 6 | 0 | ||
| APOE alleles (%) | Fisher’s exact | 0.0002** | ||
| ε4 frequency | 12 (25) | 0 | ||
| Non-ε4 frequency | 36 (75) | 46 (100) |
Data are presented as absolute numbers (n) and percentages (%). Comparisons between categorical variables were performed using Chi-square tests when all expected cell counts were≥5 and Fisher’s exact tests when expected cell counts were <5. Reported values include the χ2statistic for Chi-square analyses. Statistical significance was defined as P<0.05, P<0.01. APOE: Apolipoprotein E. *P<0.05, **P<0.01
| Feature | Severe symptoms | Moderate or mild symptoms | χ2/Fisher’s exact | P-value |
|---|---|---|---|---|
| Education level | Fisher’s exact | 6.4E-6*** | ||
| Illiterate | 11 | 0 | ||
| Primary school | 2 | 4 | ||
| High school and beyond | 0 | 7 | ||
| Living area | χ2(1, n=24)=0.74 | 0.4 | ||
| Urban area | 8 | 5 | ||
| Rural area | 5 | 6 | ||
| APOE status | Fisher’s exact | 0.24 | ||
| ε4 carriers | 7 | 3 | ||
| Non-ε4 carriers | 6 | 8 |
Data are presented as absolute numbers (n) and percentages (%). Comparisons between categorical variables were performed using Chi-square tests when all expected cell counts were ≥5 and Fisher’s exact tests when expected cell counts were <5. Reported values include the χ2 statistic for Chi-square analyses. Statistical significance was defined as***:P<0.001,APOE: Apolipoprotein E
Due to the small sample size and the presence of zero counts for APOE ε4 in the control group, the model was fitted using a Firth-corrected likelihood approach to minimize small-sample bias. Odds ratios (OR) with 95% confidence intervals (CI) and associated P-values were reported, and statistical significance was defined as P < 0.05.
RESULTS
In this study, 24 dementia patients and 23 healthy controls were recruited. The dementia group consisted of 13 males (54.2%) and 11 females (45.8%), whereas the control group included 9 males (39.1%) and 14 females (60.9%). The age of patients ranged from 60 to 92 years, with an average age of 72.3 years and a mean age at first symptom onset of 69.6 years. MMSE scores for the dementia group varied between 3 and 23, with an average score of 11.6. The highest MMSE scores among patients (22 and 23) were observed in those with high school or academic education, whereas the lowest scores in the control group (25 and 26) were found among illiterate participants. A notable family history of dementia was reported in 15 (62.5%) patients with dementia. Smoking habits and illiteracy were more prevalent in the patients group than in the controls, indicating a significant association (P = 0.0047 for smoking and P = 0.02 for education, as shown in [Table 1]).
Molecular screening for rs429358 and rs7412 APOE polymorphisms revealed the presence of the APOE-ε4 allele in 25% of patients with dementia, while this allele was completely absent in the control group. This finding supports the strong association between APOE-ε4 and dementia risk (P = 0.0002). The genotypic and allelic frequencies in Tables 1 and 2 further confirmed that APOE-ε4 is a key genetic risk factor in our cohort.
Multivariate logistic regression confirmed that APOE ε4 carriage (OR = 6.8, 95% CI: 1.3–35.6, P = 0.02) and low education (OR = 5.4, 95% CI: 1.2–25.3, P = 0.03) were independent predictors of dementia, while smoking showed a non-significant trend toward increased risk (OR = 2.7, 95% CI: 0.8–9.1, P = 0.09, [Table 3]).
| Predictor | β(Estimate) | OR | 95% CI | P-value | Significance |
|---|---|---|---|---|---|
| APOE ε4 carriage (yes vs. no) | 1.91 | 6.8 | 1.3–35.6 | 0.02* | Significant |
| Low education (illiterate vs. primary+) | 1.68 | 5.4 | 1.2–25.3 | 0.03* | Significant |
| Smoking habit (yes vs. no) | 0.99 | 2.7 | 0.8–9.1 | 0.09 | NS |
Binary logistic regression identifying independent predictors of dementia among Moroccan participants. The model included APOE ε4 carriage, educational level, and smoking habit as predictors. OR: Odds ratio, CI: Confidence interval, NS: Not significant, APOE: Apolipoprotein E. Asterisks (*) indicate statistical significance at P<0.05. The model explains approximately 42% of the variance and correctly classifies 78% of cases
The final model explained 42% of the variance (Pseudo-R2 = 0.42) and correctly classified approximately 78% of participants.
DISCUSSION
Dementia is a complex neurological condition influenced by genetic predispositions, environmental factors, lifestyle, and education level. [14] Two key polymorphisms, rs429358 and rs7412, define the three well-known alleles e2, e3, and e4, with e4 being a well-established hereditary risk factor for dementia.[11]
In the present study, APOE-ε4 was detected in 25% of the patients, while it was absent in the control group (P = 0.0002**, [Table 2]), confirming its significant association with the risk of dementia. However, the e4 allele is less common in North African populations than in Western populations[15] which might be explained by the region’s complicated demographic and genetic background.
Recent large-scale sequencing in populations of African-ancestry identified novel APOE variants (R145C and R150H) that modulate the risk conferred by the e4 allele, highlighting the importance of ancestry-specific genetic modifiers.[16] Moreover, the protective effect of higher education support fundings from African-American and Asian cohorts,[17] emphasizing the role of cognitive reserve in reducing neurodegenerative vulnerability.
Interestingly, we revealed no significant association between APOE-ε4 status and symptom severity (P = 0.24). Table 2 illustrates that both e4-carriers and non-carriers displayed comparable symptomatology. This aligns with prior studies demonstrating that while APOE-ε4 increases the risk of developing dementia, it may not directly correlate with disease progression or symptom severity.[18]
The regression analysis of our study confirmed that both genetic (APOE e4) and educational factors exert independent influences on dementia risk in Moroccan patients. This agrees with reports from Tunisia and Nigeria, where e4 carriers were 2–4-fold more likely to develop Alzheimer’s disease.[19] Our observed e4 frequency (25%) lies between North-African (15%) and Sub-Saharan (30%) averages,[20] suggesting an intermediate pattern possibly shaped by Morocco’s unique genetic admixture.
The clinical development of the illness may be influenced more by factors such as educational achievement and lifestyle choices.[21] Our results highlight the importance of education to reduce the impact of dementia symptoms. Severe symptoms were more common among individuals with lower levels of education, especially among those who were illiterate, compared to those with higher levels of education (P = 6.4 E-6, [Table 2]). This result is in line with earlier research, which found a significantly lower incidence of dementia in individuals with higher education than in those with no formal education.[22]
Smoking was also identified as a major risk factor; with higher prevalence in the dementia group than in the controls (P = 0.0047, [Table 1]). Smoking exacerbates vascular damage and oxidative stress, which is already present in people with cardiovascular disease.[23] To add, these findings suggest new avenues to investigate regarding the ethnic and genetic background, focusing on dementia within Moroccan population [Table 2].
This report shows that APOE polymorphisms rs429358 and rs7412 are common in the Moroccan population. It also provides important initial information on how the APOE-ε4 allele increases the risk of dementia. This specifically highlights the significant influence of lifestyle factors on the severity of the disease and the protective potential of cognitive activities, a healthy lifestyle, and a secure environment in reducing the risk of AD.
This study makes a critical note considering the lack of a strikingly larger sample group, suggesting chance findings. This was evident when looking at the healthy control group, which showed no prevalence for the APOE-e4 allele. Having larger cohorts would prove these results more accurate and offer deeper insights into the connection between dementia risk and the APOE polymorphisms, especially in Morocco.
In the Moroccan context, this report sheds light on the influence of lifestyle choices, particularly education and smoking, on dementia severity. To add, these findings suggest new avenues to investigate regarding the ethnic and genetic background, focusing on dementia within Moroccan populations. Future studies require biological materials, including blood, serum, plasma, and urine, while taking into account the rich, diverse and ethnic make-up of the people. Strengthening the focus on genetic aspects would assist in gaining deeper insights towards understanding the molecular actions of dementia.
Limitations
There are multiple shortcomings with this study. First, the small sample size limits the amount of power that the study has statistically, and limits the ability to generalize the findings. In this regard, participant recruitment is ongoing to achieve a balanced sample size in the subsequent phase of the study. Second, the cross-sectional method used means that there is an inability to make causal conclusions. Third, the absence of APOE-e4 in the control group may indicate a chance result that is the result of a small sample size, needing replication in larger study groups. Finally, there are multiple validated instruments used, such as the NIA-AA criteria and the MMSE; however, there are potential shortcomings in the outcomes of cognitive assessments due to the cultural and educational differences within the population.
CONCLUSION
Our analysis reaffirms the documented association of APOE-ε4 with dementia risk while emphasizing the multifaceted nature of the condition, wherein genetics, education, and lifestyle converge to influence both onset and progression of dementia. These findings underscore the necessity for further research on the etiological and predisposition factors of dementia, integrating both hereditary and non-genetic aspects to better understand and address this condition. Therefore, enlargement of the study population, completion of more comprehensive data collection, and performing thorough analyses will be essential for drawing more definitive and robust conclusions.
Acknowledgment:
This work is part of the thesis at Mohamed VI University of Sciences and Health (UM6SS).
Ethical approval:
The research/study approved by the Institutional Review Board at Comité d’Ethique de l’Université Mohammed VI des Sciences de et la Santé de Casablanca, number CE/UM6SS/12/24, dated 01st May 2024.
Declaration of patient consent:
The authors certify that they have obtained all appropriate patient consent.
Conflicts of interest:
There are no conflicts of interest.
Use of artificial intelligence (AI)-assisted technology for manuscript preparation:
The authors confirm that there was no use of artificial intelligence (AI)-assisted technology for assisting in the writing or editing of the manuscript and no images were manipulated using AI.
Financial support and sponsorship: Nil.
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