Table 2.
Incidence of cognitive impairment overall and according to key baseline characteristics, “Health and Ageing in Africa: A Longitudinal Study of an INDEPTH Community in South Africa” (HAALSI), Agincourt, South Africa, 2014–19
| Baseline characteristic | N cases, unweighted | Unweighted person-years | Weighted person-years | Incidence rate (IR), per 1000-person years (95% CI) | Incidence rate ratio (IRR) (95% CI) |
|---|---|---|---|---|---|
| Overall | 320 | 13,579.9 | 16,170.1 | 25.7 (23.0, 28.8) | - |
| Age | |||||
| 40–44 | 12 | 1,352.3 | 1,537.8 | 8.9 (5.2, 16.8) | 1.00 (ref) |
| 45–49 | 16 | 1,325.5 | 1,491.5 | 13.6 (8.4, 23.6) | 1.51 (0.72, 3.17) |
| 50–54 | 25 | 2,123.7 | 2,449.9 | 11.6 (7.9, 17.6) | 1.30 (0.66, 2.56) |
| 55–59 | 30 | 1,866.3 | 2,179.9 | 17.0 (11.8, 25.5) | 1.88 (0.97, 3.67) |
| 60–64 | 32 | 1,998.7 | 2,325.1 | 16.2 (11.6, 23.4) | 1.82 (0.95, 3.50) |
| 65–69 | 37 | 1,720.0 | 2,030.6 | 22.0 (16.0, 30.8) | 2.42 (1.28, 4.60) |
| 70–74 | 40 | 1,304.6 | 1,596.8 | 31.5 (23.3, 43.7) | 3.41 (1.82, 6.42) |
| 75–79 | 42 | 928.2 | 1,195.3 | 47.3 (35.2, 64.9) | 4.99 (2.66, 9.33) |
| 80+ | 86 | 960.6 | 1,363.2 | 93.5 (75.9, 116.3) | 9.21 (5.13, 16.5) |
| Per 5-year age increase | - | - | - | - | 1.34 (1.28, 1.41) |
| P for linear trend | - | - | - | - | <0.0001 |
| Sex/gender | |||||
| Male | 144 | 6,087.5 | 7,531.9 | 26.7 (22.6, 31.7) | 1.00 (ref) |
| Female | 176 | 7,492.4 | 8,638.1 | 24.9 (21.5, 29.0) | 0.98 (0.80, 1.20) |
| Country of birth | |||||
| South Africa | 179 | 9,687.8 | 11,618.3 | 20.6 (17.8, 24.0) | 1.00 (ref) |
| Mozambique or other | 141 | 3,880.8 | 4,539.0 | 38.8 (33.0, 46.1) | 1.62 (1.31, 2.00) |
| Educational attainment | |||||
| 0 years | 232 | 5,486.2 | 6,610.6 | 45.8 (40.3, 52.3) | 1.00 (ref) |
| 1–7 years | 61 | 5,010.8 | 5,926.4 | 13.5 (10.5, 17.6) | 0.44 (0.33, 0.58) |
| 8–11 years | 20 | 1,731.3 | 2,035.9 | 12.0 (7.8, 19.2) | 0.54 (0.33, 0.88) |
| 12+ years | 5 | 1,324.9 | 1,564.4 | 3.8 (1.6, 11.3) | 0.21 (0.09, 0.53) |
| Per year of education | – | – | 0.90 (0.86, 0.94) | ||
| Literacy | |||||
| Can read and write | 82 | 7,671.1 | 9,055.7 | 11.6 (9.4, 14.6) | 1.00 (ref) |
| Cannot read and/or write | 238 | 5,901.0 | 7,104.9 | 43.8 (38.5, 49.9) | 2.36 (1.80, 3.10) |
| Employment status | |||||
| Not working | 268 | 9,687.4 | 11,632.8 | 30.3 (26.8, 34.3) | 1.00 (ref) |
| Homemaker | 35 | 1,475.7 | 1,721.5 | 25.5 (18.4, 34.3) | 0.87 (0.62, 1.20) |
| Employed | 16 | 2,378.4 | 2,769.8 | 6.8 (4.2, 11.6) | 0.46 (0.28, 0.77) |
| Marital status | |||||
| Married | 122 | 7,362.5 | 8,677.7 | 17.7 (14.9, 21.3) | 1.00 (ref) |
| Not married | 197 | 6,211.9 | 7,484.6 | 34.8 (30.2, 40.2) | 1.84 (1.42, 2.39) |
| Household asset quintile | |||||
| 5 (richest) | 27 | 2,900.0 | 3,420.9 | 9.9 (6.9, 14.9) | 1.00 (ref) |
| 4 | 47 | 2,830.6 | 3,342.1 | 18.1 (13.6, 24.4) | 1.62 (1.02, 2.55) |
| 3 | 62 | 2,684.6 | 3,207.3 | 26.0 (20.3, 33.9) | 2.15 (1.38, 3.34) |
| 2 | 82 | 2,621.8 | 3,169.6 | 34.6 (27.8, 43.5) | 2.64 (1.73, 4.05) |
| 1 (poorest) | 102 | 2,542.9 | 3,030.0 | 42.5 (35.0, 51.9) | 3.27 (2.14, 5.01) |
| Per quintile decrease | - | - | - | 1.31 (1.20, 1.42) | |
| Smoking history | |||||
| Never smoker | 258 | 10,785.3 | 12,732.6 | 26.1 (23.1, 29.6) | 1.00 (ref) |
| Current or former smoker | 62 | 2,780.8 | 3,419.6 | 24.6 (19.2, 32.1) | 1.09 (0.81, 1.49) |
| Alcohol consumption ≥5 days/week | |||||
| No | 288 | 12,829.1 | 15,248.1 | 24.6 (21.9, 27.7) | 1.00 (ref) |
| Yes | 32 | 740.3 | 905.5 | 45.2 (32.2, 65.2) | 1.68 (1.19, 2.37) |
| Hypertension | |||||
| No | 109 | 5,689.3 | 6,728.6 | 21.2 (17.5, 25.8) | 1.00 (ref) |
| Yes | 206 | 7,676.5 | 9,174.8 | 29.2 (25.4, 33.6) | 1.03 (0.83, 1.29) |
| History of stroke, angina, or heart attack | |||||
| No | 298 | 12,900.3 | 15,344.8 | 25.1 (22.4, 28.2) | 1.00 (ref) |
| Yes | 22 | 672.9 | 817.0 | 38.5 (25.3, 61.3) | 1.45 (0.96, 2.19) |
| History of diabetes | |||||
| No | 259 | 11,215.2 | 13,319.9 | 25.0 (22.1, 28.4) | 1.00 (ref) |
| Yes | 39 | 1,415.7 | 1,698.7 | 30.3 (22.1, 42.5) | 1.05 (0.77, 1.44) |
| HIV status (DBS) | |||||
| Negative | 245 | 9,419.2 | 11,142.2 | 28.2 (24.9, 32.0) | 1.00 (ref) |
| Positive | 52 | 3,030.7 | 3,619.3 | 19.1 (14.5, 25.8) | 1.03 (0.76, 1.40) |
Note: Person-years for each baseline characteristic may not add to the total person-years, due to a small number of missing observations.
Note: IRs and IRRS are weighted to account for the probabilities of mortality and study attrition over the follow-up.
Note: Model for age is unadjusted; Model for sex/gender is age-adjusted; Model for country of birth is age- and sex/gender-adjusted; Models for all other variables are adjusted for age, sex/gender, and country of birth.