Table 4.
Effects of early-life conditions on adult cognition
| Outcomea | Measuresb | Category | Effects | Country |
|---|---|---|---|---|
| Cognitive tests | Small head circumference | Child Nutrition | 1.05 | China76,c |
| Large head circumference | Child Nutrition | 0.83 | ||
| Taller height | Child Nutrition | 0.66* | ||
| Drank milk | Child Nutrition | 0.65* | ||
| Father occupation | Child SES | 1.00 – professional | ||
| 1.01 – administrator | ||||
| 1.24 – service | ||||
| 1.75* – laborer | ||||
| Dementia | Leg length | Child Nutrition | 0.82 | Brazil75,d |
| Head circumference | Child Nutrition | 0.80 | ||
| Illiteracy | Child SES | 1.18 | ||
| Place of birth | Child SES | 1.22 – town | ||
| 1.23 – rural | ||||
| MMSE | Adult smoking | Adult Lifestyle | 0.73 | |
| Infrequently went to bed hungry | Child Nutrition | 0.89 (m), 0.89* (f) e | China72 | |
| Never/rarely suffered from severe sickness | Child Health | 0.74*** (m), 0.75***(f) | ||
| Adequate medical service for childhood illnesses | Child Health | 0.67*** (m), 0.77*** (f) | ||
| Father’s occupation professional | Child SES | 0.89 (m), 1.01 (f) | ||
| Some schooling | Child SES | 0.64*** (m), 0.63*** (f) | ||
| Survival status of parents at age 10 | Child SES | |||
| Ref: at least one | 1.00 (m), 1.00 (f) | |||
| Both parents alive | 1.03 (m), 0.88 (f) | |||
| Missing | 2.28***(m), 1.84*** (f) | |||
| Place of birth (urban) | Child SES | 0.66*** (m), 0.75*** (f) | ||
| Currently smokes | Adult Lifestyle | 0.79** (m), 1.00 (f) | ||
| Currently drinks heavily | Adult Lifestyle | 0.84 (m), 1.12 (f) e | ||
| Currently exercises regularly | Adult Lifestyle | 0.54*** (m), 0.58*** (f) | ||
| MMSE score (0–19) height | Height | Child Nutrition | 0.01** (m), 0.03*** (f) | LAC77 |
| Excellent health | Child Health | 0.05 (m), 0.14 (f) | ||
| Never hungry | Child Nutrition | 0.08 (m), 0.12 (f) | ||
| Good economic situation | Child SES | 20.08 (m), 20.22* (f) | ||
| MMSE score (0–19) knee height | Height | Child Nutrition | 20.00 (m), 0.04* (f) | |
| Excellent health | Child Health | 0.05 (m), 0.14 (f) | ||
| Never hungry | Child Nutrition | 0.09 (m), 0.12 (f) | ||
| Good economic situation | Child SES | 20.07 (m), 20.22* (f) | ||
| MMSE | Low knee height | Child Nutrition | 1.08 (m), 1.24* (f) | China78 |
| Arm length | Child Nutrition | 1.62** (m), 1.38** (f) | ||
| Went to bed hungry | Child Nutrition | 1.12 (m), 1.27** (f) | ||
| Education | Child SES | |||
| Ref: 7 years + | 1.00 | |||
| 1–6 years | 1.59** (m), 1.44 (f) | |||
| 0 years | 2.64** (m), 2.05** (f) | |||
| Place of birth (rural) | Child SES | 1.10 (m), 0.96 (f) | ||
| Current smoker | Adult Lifestyle | 0.94 (m), 0.95 (f) | ||
| MMSE –impaired or not | Had both parents alive at age 10 | Child SES | 0.94 | China74f |
| Born in urban area | Child SES | 0.83 | ||
| Leisure activity index | Adult Lifestyle | 0.80*** | ||
| Smoked in the past 5 years | Adult Lifestyle | 1.02 | ||
| Alcoholic use in the past 5 years | Adult Lifestyle | 1.04 | ||
| Regular exercise in the past 5 years | Adult Lifestyle | 1.02 |
SES, socioeconomic status; MMSE, Mini Mental State Examination; Gender models noted by: m, males; f, females.
Notes: Shown are odds ratios with the exception of Maurer and Height77 from the LAC region, which are results from linear regressions. The numbers reported reflect net effects after controlling for covariates, which varied from study to study but in most instances included age, gender and education along with other covariates.
In several studies, cognitive impairment was defined using the MMSE.97 Higher numbers indicate better cognition.
Yi et al.72 used the Chinese version of the MMSE; it tests orientation, registration, attention, calculation, recall and language. Any respondent scoring between 24 and 30 (a perfect score) has ‘normal cognitive functioning’ and anything below 24 is considered ‘impaired’.
Zhang et al.78 used the Chinese version of the MMSE; it tests orientation, calculation, recall and language. A perfect score is 30 and lower scores indicate poor cognitive ability.
Maurer77 used an abbreviated MMSE exam and minimized low literacy bias and measured cognition based on a series of orientation, memory and executive functioning tests. The resulting MMSE score ranged from 0–19 points, and tended to be left-skewed.
Wen and Gu74 used the Chinese version of the MMSE; it tests orientation, registration, copy and design, calculation, recall, naming and language.
Scazufca et al. and Zhang et al.75, 76 used a battery of validated assessments of cognitive functioning.
Measures for nutrition, health, SES and lifestyle were defined slightly differently from country to country.
Measures of childhood nutrition were defined in the following manner: (1) low knee height (lowest 10th percentile);78 (2) height [continuous (cm)];77 (3) height (m), taller (≥1 SD);76 (4) arm length (lowest 10th percentile);78 (5) leg length [continuous (cm)];75 (6) head circumference: (cm), small (<1 SD), large (≥1 SD);76 continuous (cm);75 (7) went to bed hungry [yes (no)];72, 78 (8) never hungry [time of lack of food resulting in hunger (yes (no))];77 and (9) drinking milk daily in childhood [yes (no)].76 Some measures shown in the table can also be interpreted as measures of childhood SES such as went to bed hungry.
Measures of childhood health were defined in the following manner: (1) excellent health [yes (no)];77 (2) never/rarely suffered from a severe sickness [yes (no)];72 and (3) adequate medical for childhood illnesses [yes (no)].72
Measures of childhood SES were defined in the following manner: (1) father’s occupation [professional (reference group), laborer, administrator, service];76 (2) father’s occupation professional [yes (no)];72 (3) some schooling [yes (no)];72 (4) education [7+ years (reference group), 1–6 years, 0 years];78 (5) literacy [yes (no)];75 (6) survival status of parents at the age of 10 [at least one parent died (reference group), both living, missing];72 (7) had both parents alive at age 10 [yes (no)];74 (8) good economic situation [good economic circumstances of the family (good (average/poor))];77 and (9) birthplace: place of birth – urban [yes (no)];72, 74 place of birth – rural [yes (no)];78 place of birth [city (reference group), town, rural].75
Measures of adult lifestyle were defined in the following manner: (1) smoking: current smoker [yes (no)];72, 78 smoked in the past 5 years [yes (no)];74 ever smoked [no (yes)];75 (2) drinking: drinks heavily [defined as 400 g of beer per day (yes (no))];72 drank in the past 5 years [yes (no)];74 (3) exercising: exercises regularly [yes (no)];72 regularly exercised in the past 5 years [yes (no)];74 and (4) leisure activity index (an index developed to encompass a range of activities shown to impact health conditions at older ages including gardening, raising pets, outdoor activities, reading, playing cards, listening to radio, watching television and social activities).74
The significance levels reflect the reporting of 95% confidence intervals. The full models reported in this study included other prenatal factors but did not report their effects in the full model.
In baseline models (results not shown), the effects of leg length and head circumference were significant. In the final model reported in the table these effects disappear. In a model with exposure adjusted for age and gender, the effects of leg length and head circumference remain strong even after adjusting for adult SES and lifestyle.
Yi et al.72 reported effects that were of marginal significance (P <0.10). The odds ratios for males who infrequently went to bed hungry as well as that for females who currently drink heavily were marginally significant.
Only select variables were included from Wen and Gu74 due to space constraints.
P <0.05;
P <0.01;
P <0.001.