TABLE 1.
Characteristics of studies included in the systematic review
| Study (year) | n 1 | Year sampled | Follow‐up period, year | Country | Study design | Lipid measured | Outcome (effect measure) | Risk estimate | Diagnostic criteria | Mean (SD) age at baseline | Age range (baseline) | Female (%) | Covariates adjusted for in analysis |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Gong (2021) 27 | 273,262 | 2006‐2010 | 11.8a | United Kingdom | Prospective cohort study | TC, LDL, HDL | Incident dementia | HR | ICD‐10 codes via medical records, death registry | 56·3 (8 0) 2 | ·· | 100·0 | Age, BMI, CVA, diabetes, drugs b, c SBP, SES, smoking |
| Gong (2021) 27 | 228,964 | 2006‐2010 | 11·7a | United Kingdom | Prospective cohort study | TC, LDL, HDL | Incident dementia | HR | ICD10 codes via medical records, death registry | 56·7 (8·2) 2 | ·· | 0·0 | Age, BMI, CVA, diabetes, drugs b, c, SBP, SES, smoking |
| Iwagami (2021) 2 8 | 636,262 | 1992‐2009 |
7·4a (4·6, 10·4) |
United Kingdom | Retrospective cohort study | TC, LDL, HDL, TG | Incident dementia | HR | Medical codes via general practice records (CPRD GOLD) | 52·0 (7·2) | ·· | 49·9 | Age, BMI, country, CVA, CVD, diabetes, drugs b, c, d, ethnicity, EtOH, SES, sex, smoking, AF, COPD |
| Liang (2020) 19 | 744 | 1972‐1987 | 21·2* | Finland | Prospective cohort study | TC | Incident dementia | HR | DSM‐IV criteria via MMSE | 50·4 (6·0) | 40‐64 | 62·1 | Age, APOE genotype, BMI, BP, CVD, death, diabetes, education, glucose level, physical activity, sex, smoking |
| Sabia (2019) 29 | 7899 | 1985‐1988 | 24·7a | ||||||||||
| (19·1, 29·3) | United Kingdom | Prospective cohort study | TC | Incident dementia | HR | ICD10 codes via medical records | 50·4 (2·3) | 45‐55 | 32·4 | Age, CVD, ethnicity, education, marital status, SES, sex, | |||
| Svensson (2019) 22 | 1106 | 1990 | ·· | Japan | Prospective cohort study | TC, LDL, HDL, TG | Incident dementia, MCI | OR | DSM‐IV criteria via MMSE, WMS‐R, CDT, CDR scale | 54·3 (5·5) | ·· | 63·1 | Age, BMI, diabetes, drugs b, education, EtOH, HTN, sex, smoking |
| Vu (2019) 21 | 10,119 | 1967‐1973 | ·· | United States | Prospective cohort study | TC | Incident dementia | HR | ICD9 codes via Medicare claims | 35·3 (5·5) | 23‐47 | 32·4 | Age, death, education, ethnicity, No. of medical visits prior to diagnosis, sex |
| Toro (2014) 30 | 222 | 1993‐1995 | 14 a | Germany | Prospective cohort study | TC | Incident dementia, MCI | OR | DSM‐III via clinical assessment | 62·4 | 60‐64 | 46·8 | APOE genotype, BMI, diabetes, education, HTN, SES, sex |
| Exalto (2014) 34 | 9480 | 1964‐1973 | 36·1 (4·3)* | United States | Retrospective cohort study | TC | Incident dementia | HR | ICD9 codes via medical records | 46·1 (4·3) | 40‐55 | 55·1 | Age, BMI, education, depressed mood, diabetes, head trauma, lung function, obesity, SBP, sex, smoking |
| Rönnemaa (2011) 42 | 2268 | 1970 | 29* | Sweden | Prospective cohort study | TC | Incident dementia, AD, VD, FTLD | HR | DSM‐IV criteria via medical records | 49·6 (0·6) | ·· | 0·0 | Age, education |
| Solomon (2009) 45 | 9844 | 1964‐1973 | ·· | United States | Retrospective cohort study | TC | Incident AD | HR | ICD9 codes via medical records | 42·4 (1·7) | 40‐45 | 54·1 | Age, BMI, CVA (late‐life), diabetes, education, ethnicity, HTN, sex |
| Mielke (2010) 44 | 648 | 1968‐1969 | 32* | Sweden | Prospective cohort study | TC | Incident dementia, AD | HR | DSM‐III criteria via medical records | 46·8 2 | 38‐60 | 100·0 | Age, BMI, DBP, education |
| Whitmer (2005) 18 | 8845 | 1964‐1973 | 26·7* | United States | Retrospective cohort study | TC | Incident dementia | HR | ICD9 codes via medical records | 42·0 (1·4) | 40‐44 | 53·7 | Age, ethnicity, education, sex |
| Rosengren (2005) 43 | 7402 | 1970‐1973 | 23* | Sweden | Prospective cohort study | TC | Incident dementia | HR | ICD 8/9 codes via hospital records/death registry | 51·5 (2·3) | 47‐55 | 0·0 | Age |
| Kivipelto (2005) 35 | 1409 | 1972‐1987 | 21·0 (4·9)* | Finland | Prospective cohort study | TC | Incident AD | OR | DSM‐IV criteria via MMSE | 50·6 (6·0) | 40‐64 | 62·1 | Age, sex, education, BMI, SBP, follow‐up duration |
| Kivipelto (2001) 36 | 1400 | 1972‐1987 | 20·9 (4·9)* | Finland | Prospective cohort study | TC | Incident dementia | OR | DSM‐IV criteria via MMSE | 50·4 (6·0) | 40‐64 | 62·1 | Age, BMI, CVA, CVD, education, EtOH, smoking |
| Kivipelto (2001) 20 | 1352 | 1972‐1987 | 21·0 (4·9)* | Finland | Prospective cohort study | TC | Incident MCI | OR | MCADRC criteria | 50·4 (6·0) | 40‐64 | 62·1 | Age, BMI |
| Notkola (1998) 46 | 444 | 1959‐1974 | 30* | Finland | Prospective cohort study | TC | Incident AD | OR | DSM‐III‐R criteria | ·· | 40‐59 | 0·0 | Age, APOE genotype |
Number of participants from the original study who were eligible for analysis in the present review.
Due to data restrictions, values were based on the entire study sample rather than the eligible sub‐sample for our study.
*Follow‐up period in mean (SD) years; aFollow‐up period in median (IQR) years.
Drugs: b = lipid‐lowering, c = antihypertensive, d = hypoglycemic (antidiabetic).
Abbreviations: AD, Alzheimer's disease; APOE, apolipoprotein E ε4; AF, atrial fibrillation, BP, blood pressure; BMI, body‐mass index; CVD, cardiovascular disease; CVA, cerebrovascular accident/disease; COPD, chronic obstruction pulmonary disease; CDR, Clinical Dementia Rating; CPRD, Clinical Practice Research Datalink; CDT, clock drawing test; DSM, Diagnostic and Statistical Manual of Mental Disorders; DBP, diastolic blood pressure; EtOH, alcohol use; FTLD, frontotemporal lobe dementia; HDL, high‐density lipoprotein; HR, hazard ratio; HTN, hypertension; ICD, International Classification of Diseases; LDL, low‐density lipoprotein; OR, odds ratio; MCADRC, Mayo Clinic Alzheimer's Disease Research; MCI, mild cognitive impairment; MMSE, Mini‐Mental State Examination; RR, risk ratio; SES, socioeconomic status; SBP, systolic blood pressure; TC, total cholesterol; TG, triglyceride; VD, vascular dementia; WMS‐R, Wechsler Memory Scale‐Revised.