Introduction
Materials and methods
Search methods
Inclusion criteria, data extraction and validity assessment
Analysis
Study Name | n | Population | Dose & type of oral iron | Baseline Iron Status | Study duratn, Drop-outs | Cognitive tests* |
---|---|---|---|---|---|---|
Iron 34 Pl 30 | S Africa-mothers, 18-30 yrs
Pre-menopausal women
| 125 mg/d as pills |
Anaemic - Hb 9-11.5 g/dl, SF 10-12 μg/L | 29 wks, Iron 2 Pl 4 |
Raven's CPM (IQ), Wechsler's DS (M, Ps)
| |
Iron 40 Pl 41 | USA-adolescents, school, mean age 16.2 and 15.7
Children 6-18
| 260 mg/d EFe as capsules |
Iron Defic - Hb>11.5 g/dl (Af American), Hb>12 g/dl (white), SF<12 μg/L for all | 8 wks, Iron 1 Pl 2 | Visual Search and Attention (AC), Hopkin's Verbal Learning Test (M), DS Modalities (Ps), Attention. | |
Elwood 1970 [20] | Iron 26 Pl 21 | UK - women >20 yrs
Pre-menopausal women
| 150 mg/d as tablets |
Anaemic - HB<10.5 g/dl | 8 wks, Iron 0 Pl 0 |
Mazes test (AC), Serial Sevens (M), Peg board (Ps), E test, card sorter. |
Iron 32 Pl 16 | India-School boys-recipients of free noon meal, 8-15 yrs
Children 6-18
| 30 or 40 mg/d as tablets |
Anaemic - Hb<10.5 g/dl, Iron Defic and/or Repl- rest | 8.5 wks, Iron 0 Pl 0 |
Mazes test (AC), Visual Memory Test (M), Wechsler's Digit span (Ps), Clerical task | |
Groner 1986 [22] | Iron 19 Pl 19 | USA-pregnant women, 14-24 yrs
Pre-menopausal women
| 60 mg/d EFe as capsules |
Iron repl - mean Hb>12 g/dl, SF 40-60 μg/L | 4 wks, Iron 3 Pl 10 |
Vocab (IQ), DS (M, Ps), Arithmetic (SA), Consonant trigram, Rey AVL, Digit Span |
Iron 83 Pl 83 | India-School girls, under privileged, 8-15 yrs
Children 6-18
| 60 mg/d EFe as tablets |
Anaemic - Hb<10.5 g/dl, Iron Defic and/or Repl-rest | 17.2 wks, Iron 18 Pl 18 |
Mazes test (AC), Visual Memory (M), Wechsler's Digit span (Ps), Clerical | |
Iron 303 Pl 299 | Mexico-school children, mean age 7.0
Children 6-18
| 30 mg/d as tablets |
Iron Defic and/or Repl - Hb>9 g/dl | 21 wks, Iron 38 Pl 49 | Distractibility (AC), Peabody PV (IQ), Vis Memory (M), Maths (SA), Sternberg** | |
Iron 57 Pl 59 | New Zealand-female high school students, 12.5-17.9 yrs
Children 6-18
| 105 mg/d EFe as tablets |
Iron defic - Hb>12 g/dl, SF<12 μg/L | 8 wks, 5 across whole study | Visual Search and Attention (AC), Hopkin's Verbal Learning (M), Stroop task, Reading span | |
Lynn & Harland 1998 [15] | Iron 208 Pl 205 | England - teenagers at 7 comprehensive schools, 12-16 yrs
Children 6-18
| 17 mg/d EFe as tablets |
Iron Defic - any Hb, SF<12 μg/L ??and??? Iron Repl - the rest | 16 wks, Unclear, ~200 over study? |
Raven's CPM (IQ)
|
Iron 76 Pl 76 | USA-Women, aged 18-35 yrs
Pre-menopausal women
| 60 mg/d EFe as pills |
Anaemic - Hb 10.5-11.9 g/dl plus 2 aFeSIs, Iron Defic - Hb = 12 g/dl plus 2 aFeSIs, Iron Repl - Hb = 12 g/dl without 2 aFeSIs | 16 wks, Iron 20 Pl 19 | Cog Abilities-attention (AC), Cog Abilities - memory (M), Cog Abilities - learning (SA), Shipley Inst Scale (IQ) | |
Pollitt 1989 [24] | Iron 678 Pl 678 | Thailand-school children, 9-12 yrs
Children 6-18
| 4 mg/kg/d EFe as tablets |
Anaemic Hb<12 g/dl and SF<10 μg/L or TS<16%, Iron Defic Hb>12 g/dl and SF<10 μg/L or TS<16%, Iron Repl - rest | 16 wks, Not reported |
Raven's CPM (IQ), Mathematics (SA), Thai language |
Iron 59 Pl 60 | Indonesia-primary school children, mean age 10.7 to 11.1 yrs
Children 6-18
| 2 mg/kg/d EFe as tablets |
Anaemic - Hb<11 g/dl, TS<15%, Iron Repl - Hb>12 g/dl, TS>20% | 13 wks, Iron 0 Pl 0 | Raven's CPM (IQ), Bourden-wisconsin concentration, Maths, Language, Biology, social science | |
Soemantri 1989 [25] | Iron 71 Pl 59 | Indonesia-primary school children, mean age 10.4
Children 6-18
| 2 mg/kg/d EFe tablets |
Anaemic - Hb<11 g/dl, TS<12%, Iron Repl - Hb>12 g/dl. TS <20% | 13 wks, Iron 0 Pl 0 |
Raven's CPM (IQ), Maths (SA), Language, Biology, social science |
Iron/d 112 Iron/wk 102 Pl 99 | Thailand-School children, mean age 9.6 to 9.7
Children 6-18
| 60 mg/d or/wk EFe, tablets |
Iron Repl - Hb>8 g/dl, SF>20 μg/L | 16 wks, Iron/d 1 Iron/wk 4 Pl 1 |
Test of Non-Verbal Intelligence (IQ), Maths (SA), Thai Language |
Random-isation Described/Allocation Concealment | Researcher/Outcome Assessor/Participants Masked to intervention | Change in iron status OR 12+ wks?* | All those randomised included in outcomes?/Reason for dropouts reported? | Potential for funding bias** | Study data useable in meta-analysis? | |
---|---|---|---|---|---|---|
Beard 2005
| Partially/Unclear | Unclear/Unclear/Yes |
Yes (SF, 29 wks) | No/Partially | Moderate | Yes |
Bruner 1996
| Yes/Unclear | Yes/Unclear/Yes |
Yes (Hb & SF) | No/Yes | High | No (no raw data, only regression) |
Elwood 1970
| No/Unclear | Unclear/Yes/Yes |
Unclear (p-values not presented) | No/Partially | High | Yes |
Gopaldas 1985
| Partially/Unclear | No/No/Yes |
Anaemic & Iron repl: Yes (Hb) | Yes/Yes (no drop-outs) | High | Yes |
Groner 1986
| No/Unclear | Yes/Yes/Yes |
Yes (Hb) | No/Yes | Moderate | Yes |
Kashyap 1987
| Partially/Unclear | Unclear/Unclear/Yes |
Anaemic & Iron repl: Yes (Hb, 17 wks) | No/Partially | Moderate | Yes |
Kordas 2005
| Yes/Unclear | Yes/Yes/Yes |
Yes (21 wks) | No/Partially | Moderate | No (only z-scores) |
Lambert 2002
| No/Unclear | Yes/Unclear/Yes |
Yes (SF, not Hb) | No/No | Moderate | No (no variance data) |
Lynn & Harland 1998
| Yes/Unclear | Yes/Yes/Yes |
Iron Defic & Iron repl: Yes (16 wks) | Unclear/No | High | Yes |
Murray-Kolb 2007
| Yes/Unclear | No/Yes/Yes |
Anaemic & Iron repl: Yes (SF, not Hb, 16 wks),Iron defic: No (not SF or Hb) | No/Partially | Moderate | No (reported only as z-scores) |
Pollitt 1989
| No/Unclear | Unclear/Unclear/Yes |
Anaemic, Iron defic & Iron repl: Yes (Hb, SF, 16 wks) | No/No | Moderate | Yes |
Soemantri 1985
| No/Unclear | Unclear/Unclear/Unclear |
Anaemic: Yes (Hb, 13 wks)
Iron repl: No (Hb) | Unclear/No | Moderate | No (no variance or SD data) |
Soemantri 1989
| No/Unclear | Unclear/Unclear/Yes |
Anaemic & Iron repl: Yes (Hb, 13 wks) | No/No | Moderate | Yes |
Sungthong 2004
| Yes/Yes | Yes/Yes/Yes |
Yes (SF & Hb, 16 wks) | No/Yes | Low | Yes |
Results
Review process
Study characteristics
Validity of studies
Outcomes
Attention/Concentration
Cognitive domain | Age group | Standardised mean difference (95% CI) | Number of participants/studies | Heterogeneity - I2 test |
---|---|---|---|---|
Attention & concentration | Children aged 6-18 | 0.62 (0.26 to 0.98)* | 132/2 (4 arms)** | 0% |
Pre-menopausal women | 0.53 (-0.06 to 1.12) | 47/1 | Not relevant | |
Intelligence | Children aged 6-18 | 0.02 (-0.22 to 0.27) | 2289/4 (9 arms)** | 82% |
Pre-menopausal women | 0.62 (0.15 to 1.10)* | 76/2 | 0% | |
Memory | Children aged 6-18 | 0.33 (-0.19 to 0.85) | 132/2 (4 arms)** | 35% |
Pre-menopausal women | 0.09 (-0.31 to 0.50) | 123/3 | 18% | |
Psychomotor | Children aged 6-18 | 0.19 (-0.17 to 0.54) | 132/2 (4 arms)** | 0% |
Pre-menopausal women | 0.09 (-0.32 to 0.50) | 123/3 | 21% | |
Scholastic aptitude | Children aged 6-18 | 0.03 (-0.63 to 0.69) | 1799/3 (6 arms)** | 96% |
Pre-menopausal women | 0.77 (-0.08 to 1.62) | 25/1 | Not relevant |